IMBSIR 76-1141

Study of Initial Stages of Wear

by Electron Channeling

I. Measurement of Plastic Strain in Copper Due to Sliding Wear

II. Quantitative Methods in Wear Debris Analysis

A. W. Ruff

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

September 1976

Final Report

N000 14-76-F-002

Prepared for Office of Naval Research

Department of the Navy

Arlington, Virginia 22217

NBSIR 76-1141

STUDY OF INITIAL STAGES OF WEAR

BY ELECTRON CHANNELING

I. Measurement of Plastic Strain in Cooper Due to Sliding Wear

II. Quantitative Methods in Wear Debris Analysis

A. W. Ruff

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

September 1976

Final Report

NOOO 14-76-F-002

Prepared for Office of Naval Research

Department of the Navy

Arlington, Virginia 22217

U S. DEPARTMENT OF COMMERCE. Elliot L. Richardson, Secretary

Edward O. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

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NBSIR 76 -1141

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4. TITLE (and Subtitle)

S Study of Initial Stages of Wear by Electron

Channeling

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Final Report

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A. W. Ruff

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A. W. Ruff

National Bureau of Standards

Washington, D.C. 20234

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September 1976

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19. KEY WORDS (Continue on reverse aide it necessary and Identify by block number)

Copper;' electron channeling; electron microscope; metals; particle analysis;

plastic deformation; surfaces; wear; wear debris; x-ray analysis.

20. ABSTRACT (Continue on reverse aide If necessary and Identify by block number)

Wear experiments have been conducted to determine the plastic strains that are troduced in the surface material near sliding wear tracks. Both oil lubricated and

y sliding experiments have been carried out at different sliding distances on surces of copper. The strain values were determined from selected area electron channel

-

g patterns obtained using a scanning electron microscope from regions as small as ym in size and 0.05 ym deep around the wear track. A deformed calibration specimen

I I 1473 EDITION OF 1 NOV 65 IS OBSOLETE

S/N 0102-014-6601 ! DD FORM

1 JAN 73 SECURITY CLASSIFICATION OF THIS PAGE (When Dale Bnlarad)
UNITY CLASSIFICATION OF THIS P AGEfWhen Data Entered) was used to relate electron channeling band contrast to deformation strain. Strain

maps were obtained on the wear surface lateral to the wear track and also below the

surface using electropolishing metal removal techniques. Particular attention was placed on the near-surface strain values. In all cases, the maximum strain was found

at the wear surface located at the track center and the strains decreased uniformly

with depth. Significant, large strains were also found outside the wear tracks. The

results are compared with those previously reported for iron and with recent

theoretical models.

Wear debris has been removed from a number of test systems and analyzed using

different methods. Those methods produced specific information concerning the

particulate size and composition. A magnetic debris recovery method was quantitativel)

evaluated using actual debris samples and also using collections of manufactured

particulates having known sizes and compositions. Small 5 pm diameter Si02 spheres, some containing nickel, were used to simulate debris. Other particulates of iron and

nickel in different size ranges were also used in order to investigate such matters

as size resolution, lubricant dilution techniques, particle overlap difficulties, and

the general problem of calibration of debris recovery systems. A comparison between

chemical analysis and particulate analysis findings is presented. The application

of optical and electron microscope methods and x-ray microanalysis in characterizing

the wear particulates was carried out directly on the recovery substrate; those

techniques are described.

SECURITY CLASSIFICATION OF THIS PAGE (When Date Entered)
Measurement of Plastic Strain in Copper Due to Sliding Wear

A. W. Ruff

Metallurgy Division

National Bureau of Standards

Washington, D.C. 20234

ABSTRACT

Wear experiments have been conducted to determine the plastic strains that are introduced in the

surface material near sliding wear tracks. Both oil

lubricated and dry sliding experiments have been

carried out at different sliding distances on sur- faces of copper. The strain values were determined

from selected area electron channeling patterns

obtained using a scanning electron microscope from

regions as small as 10 pm in size and 0.05 pm deep

around the wear track. A deformed calibration

specimen was used to relate electron channeling

band contrast to deformation strain. Strain maps

were obtained on the wear surface lateral to the

wear track and also below the surface using

electropolishing metal removal techniques.

Particular attention was placed on the near- surface strain values. In all cases, the maximum

strain was found at the wear surface located at

the track center and the strains decreased uniformly

with depth. Significant, large strains were also

found outside the wear tracks. The results are compared with those previously reported for iron

and with recent theoretical models.

INTRODUCTION

Investigations into the mechanisms of the wear

of materials are of crucial importance if significant

progress is to be made in reducing wear or even in

monitoring wear rates. The analysis of wear debris

recovered from lubricants and wearing systems has

proven (1-3) to offer valuable information on the

condition of such systems, however, the significance

of debris analysis (if purely empirical methods are

to be exceeded) rests on an understanding of debris

formation mechanisms. Recent years have seen several

important contributions (4,5). In particular,

the delamination theory of wear (6) postulates a wear particle formation process that appears to agree

with certain observations. That approach incorporates

certain material parameters in the model used and

recognizes the influence of imperfections, e.g. voids,

inclusions and the free surface. One unusual aspect

of that model involves surface softening, i.e.,

Contribution of NBS. Not subject to copyright.
dislocation density and flow stress

gradients such that both quantities increase initially

with distance inward from the surface. That circumstance develops according to this picture as a result

of surface image forces on the dislocations produced

during the wear deformation that lead to a local loss

of dislocations as a result of glide out of the surface. Some experimental evidence in copper and

aluminum has been cited (7) to support this idea

although recent measurements on iron (8) have not

found any evidence for the surface softening that

would be expected. This paper presents some results

obtained on high purity copper specimens tested in

sliding wear that also indicates an absence of any

surface softening effects. However, it is important

to note that this aspect of the delamination model

is not crucial (in our view) , Indeed the factors

responsible for subsurface crack formation and

propogation are probably complex and numerous.

Data such as those presented here concerning the

strain distribution in the material near wear tracks

are required if an accurate understanding of the

inhomogeneous deformation processes involved

in such matters are to be understood.

EXPERIMENTAL

The constant velocity, sliding wear tester

used in these studies has been described previously

(8) . A motor driven cam transmitted a reciprocating

velocity (2.0 cm/s) to a platform on which the test

specimen was fastened. The linear motion was adjustable up to 2 cm. A load was applied through

a pin from above the specimen. A bearing ball of

2.4 mm diameter (52100 steel) was fastened at the

end of this pin. The frictional force at the con- tact surface could be measured during the wear

test using strain gauges. Tests of durations from

5 to 500 cycles were conducted under either dry

or oil lubricated conditions.

Specimens were fabricated from 99.999% copper

sheet, 0.5 mm thick (impurity content 10 ppm C,

5 ppm Zn, others <1 ppm). Specimens were cut to

size 1 cm x 2.5 cm and then annealed for 2 hours

at 1000°C in an evacuated, sealed quartz tube.

Prior to wear testing each specimen was electropolished about 20 minutes in a solution of 67%

phosphoric acid: 33% water. In experiments involving

strain measurements below the worn surface, the same electropolishing procedure was followed in order to remove material in a strain- free manner. An approximate depth of 10 ym of copper was removed from each

side of the sheet in 24 minutes.

- 2

-
Specimens were clamped down around the edges

within the specimen tray in the wear tester. In

tests involving oil lubrication, the specimen tray was filled with SAE 30 weight automotive oil prior

to testing. The oil had been previously filtered

through a 1.2 ym filter to remove solid impurities.

Tests were conducted by mounting the electropolished

specimen in the tray, adding oil if desired, loading

the pin to the desired value, starting the drive

motor and carefully lowering the pin into contact

with the specimen. The wear specimen and bearing

ball were examined after each test (after cleaning

with a solvent) using optical microscopy and scanning

electron microscopy (SEM) techniques . The SEM had

been modified for selected area electron channeling

pattern (SACP) studies involving the rocking beam

mode (9,10) of operation. The specimen was oriented

normal to the electron beam and operated in the

emissive (secondary and backscattered electron) mode.

The minimum selected area realizable was about 10 ym

across (approximately circular) at a specimen- lens

distance of 2 mm. The angular extent of the SACP

was about 15 degrees. The microscope was operated at

20 kV and a specimen current of 2 x 10" amperes.

RESULTS AND DISCUSSION

Selected Area Channeling Patterns

Previous workers (9-11) have used either the

line width or the contrast associated with a particular channeling line as a measure of the strains

present in the channeling volume. Channeling lines

of different hkl indices (corresponding to the hkl

of the planes involved in the channeling process)

exhibit different line broadening amounts; the

higher index lines are more sensitive to lattice

strain. Hence it is necessary to systematically

employ the same {hkl} channeling line and to

calibrate the effect of strain on that line using

a suitably deformed specimen. In this study, the

111 channeling line in copper was used. The contrast

of the line was determined according to the relation

C = {I (max) - I (min) }/I (avg) where I is the detected

(amplified) signal level. The method of use of the

gain and DC level controls on the SEM that permited

quantitative contrast values to be determined from

photographs of the signal trace on the recording

screen has been described (8)

.

An example of an SACP taken from one grain in an undeformed copper

specimen is shown in Fig. 1. The 111 band is labeled

and higher order channeling lines are clearly visible

as the fine structure in this pattern.

- 3-
Strain Calibration Specimen

A copper rod, 4.5 mm in diameter, was cut to a length 12.5 mm. Two flat surfaces were ground on opposite sides, one parallel to the rod axis, the

other at an angle of about 1.2° to the axis. This

resulted in a tapered specimen, 1.35 mm thick at one

end and 1.62 mm thick at the other end. The specimen

was then electropolished, sealed in an evacuated

capsule and annealed for 2 hours at 980°C. The

specimen was deformed in compression between two steel

plates on which teflon films had been placed until a uniform thickness was reached. In this manner, a gradient in applied true strain from zero to 271 was produced

SACP from two different regions of the calibration specimen are presented in Fig. 2. Superimposed

on these patterns are four signal traces from different regions of the pattern and the two reference

signals (white and black levels) that are used in

determining the average contrast. Reproducible

contrast values were obtained using this method of

signal presentation and measurement over the contrast

range of 0 to 10%, provided that each specimen was mounted carefully in the SEM in a reproducible manner. A strain determination could be completed at a given

location in a matter of minutes using this method.

A sufficient number of grains with 111 channeling bands prominent in their patterns were

located and the contrast gradient that resulted from

the introduced strain gradient mapped out along the

length of the calibration specimen. The results of

SACP contrast measurements are given in Fig. 3.

Contrast values below 1% were not measured due to

poor precision. Strains greater than about 27% in

copper cannot reliably be determined by this method.

Previous studies of stainless steel (9,10) have shown

that strains in excess of about 20% (tensile) could

not be reliably measured using SACP methods. In iron

(8) strains greater than about 17% (compressive)

could not be determined by this method.

Sliding Wear Experiments

Studies were conducted using progressively larger

sliding distances. The specimen surfaces were all

electropolished for about 15 minutes immediately before wear testing. The oil lubricated tests will be

described first. The smallest sliding distance was

0.17 m (5 machine cycles). The contact along the

track was reasonably uniform as shown in Fig. 4. A

number of grains in and adjacent to the wear track

were selected and SACP were obtained. Two of the

- 4-
locations (A and D) on the surface in Fig. 4 produced

the SACP shown in Fig. 5. The higher strains present

in the track center lead to the lower contrast pattern

seen in Fig. 5a. The strains determined from these

SACP using the contrast-strain relation (Fig. 3) are plotted in Fig. 7 and will be discussed later. The

grain configuration in this specimen is seen in Fig. 4

in the channeling contrast that results from grain

orientation differences.

Two other sliding distances were studied, 1.7

and 17 m, under the same conditions in other respects.

Figure 5a shows a portion of the wear track formed

under oil lubricated conditions at the latter distance. The track is characterized by long, shallow

groove markings in the sliding direction and by a lip of material at the track edge. Extensive plastic

deformation has taken place in the surface material

at the wear track. Adjacent to the track, slip

lines can be seen in many of the grains (arrow,

Fig. 5a) . The amount of slip decreases rapidly with

distance from the track edge. One test was con- ducted in which only a light film of oil was placed

initially on the bearing pin contact. Under this

limited lubrication condition the track appearance

remained similar to that seen in Fig. 5a. The dry

sliding tests produced a significantly different

track appearance (Fig. 5b). The track was wider,

more irregular and the groove markings within the

track were much less prominant. The frictional

coefficient over the last portion of the dry tests was typically 1.5, considerably higher than that

found for oil lubricated tests of about 0.7. It

is believed that a relatively "soft" loading pin

suspension in the wear tester is responsible for some of the track features found, as a result of the

higher frictional forces associated with the dry

tests

.

Strain Measurements

Shortly after each wear test was completed,

SACP were obtained from the surface at various

distances from the wear track center. A grain was selected that was sufficiently large, suitable in

orientation and positioned across the track from

which the SACP were obtained. At each location

at least four values of contrast across the 111

band were obtained and averaged. The associated

strain value was determined from the calibration

curve (Fig. 3). The results are given in Fig. 7.

A common feature of the lateral strain distribution is the rapid decrease in strain near and

beyond the edge of the wear track. However, the

surface strains still extend considerable distances

- 5-
from the apparent edges of the wear tracks. For

example, at a sliding distance of 17 m under oil,

the strain at the track edge (70 pm) was about

24% and decreased to about 5% at twice that distance from the center. In two cases the strain

could be measured over the entire track width

and was found to increase steadily as the track

center was approached. Since strains greater

than about 36% could not be measured by the SACP

method it was not possible to map out the entire

surface distribution of strains in all cases. However, it appears that for sliding distances up

to 17 m the maximum strain values at the surface

are found at the track center position. Comparison

of the 17 m sliding distance experiments under dry,

oil film and oil bath conditions reveals that larger

strains and a broader distribution are produced

under dry conditions but otherwise the strain distribution is similar.

Measurements of the strain distribution with

depth below the original surface were conducted after

electropolishing for appropriate times to remove a specific thickness of material. The original track

center could be located in all cases since the

surface depression there persisted through the

electropolishing steps. The results determined

from three 17 m sliding distance experiments are shown in Fig. 8. In all cases the measured strains

extend further lateral to the wear track than its

edges (marked by arrow) even at subsurface locations.

Within the track the maximum strains are found at

the surface and decrease smoothly with depth, van- ishing at depths of 50 pm or more depending on conditions. At any specific depth the maximum strain

was found under the wear track center.

Relation to Other Studies

The strain measurement method described here

has previously been applied to wear track deformation studies in iron (8)

.

Qualitatively the results

were similar in these two materials. The strain

values in both materials decreased with depth below

the worn surface and decreased with lateral distance

from the wear track. At a given sliding distance,

17 m in oil, the strains in copper are about twice

as large as in iron, both at the surface and at

particular depths. The track center strains

(50g, 17m) vanish at 30ym depth in iron and at about

50 pm depth in copper. Under dry conditions, the

difference appears even greater. The surface slip

- 6-
markings adjacent to the wear track in copper were

more prominent than in iron, consistent with the

evidence of more extensive plastic deformation.

Several previous studies of wear track material

have been conducted in copper and similar metals.

Some of those developed information that can be

related to the results presented here. Bailey and

Gwathmey (12) studied the effects of dry sliding

wear on various orientations of copper single crystals. This included dislocation etch pit studies

that demonstrated the rapid decrease in dislocation

density with distance out from the wear track edge.

Slip line observations adjacent to the tracks were

consistent with those found here. They found con- siderable work hardening in the wear track and

reported evidence of recrystallization when the

deformation temperature reached 250 C. X-ray

diffraction studies (averaged over 250 pm regions)

of sliding on copper single crystals (13) revealed

crystal plane bending and rotations resulting from

slip deformation. The deformed layer was described

as microsrystalline in structure. In another dry

sliding study in copper (14) metallographic

examination revealed evidence of recrystallization

associated with the material below the worn

(deformed) surface material. Microhardness measurements were conducted that showed decreases with

distance from the wear surface that are consistent

with the strain profiles found here. Other microhardness measurements have been reported for copper

(15,16) involving material in and adjacent to sliding

wear tracks that however, show some disagreement with

respect to the trend of hardness values. Because of

the influence of the free surface on hardness measurements (8) it is believed that quantitative comparisons

may not be justified. Recently, Bill and Wisander

(17,18) have reported wear track studies in copper

under various conditions (including liquid methane

environments where oxidation should be relatively

slow) . They found evidence for a small cell -sized

recrystallized region near the wear surface in which

the dislocations involved were predominantly located

in the cell walls. The reported cell size of 5000A0 was determined using transmission electron microscopy

techniques on thin foils cut from the worn specimens.

It is known from studies of the microstructure of

plastically deformed copper that small cell sizes

characterize relatively high levels of strain

(19) and hence those results are consistent

with the SACP broadening found here. Lacking a detailed theory of SACP broadening, it is not presently

possible to distinguish uniform dislocation arrangements from cell -structure arrangements based on SACP

data alone. Either possibility can be associated,

- 7-
however, with the high level of deformation and

hardening that is believed present.

The delamination model of wear (6) includes

among other features the consideration of a "soft

surface" region that forms during the wear deformation by the loss of dislocations through the

free surface. The calculated depth of this region

for copper was reported as about 10 urn although

for the higher yield stress values usually

associated with copper (4 MPa) a more

representative figure would be 0.5 pm. The results

reported here are not consistant with that picture,

rather, they indicate a hardened layer at the surface

and a decrease of strain with distance below the

surface. The SACP are obtained from layers of

material about 500 X thick and about 10-15 pm in

lateral dimensions. Thus the SACP obtained from

the as -worn surface in copper are associated with

the near-surface layer that is of interest in the

delamination theory.

Detailed knowledge of the microstructure of

the near surface region is being accumulated.

Recent results (18) indicate that a transition in

microstructure occurs below the worn surface. This

microstructure transition may develop as a result

of dynamic recrystallization processes that are driven by thermal and mechanical effects. If

correct, that microstructure may alternatively

satisfy the requirements for delamination processes

that produce the wear debris particles frequently

found.

SUMMARY

1) Strains up to 351 have been measured

using a calibrated selected area electron channeling

pattern method from wear track material in copper.

Both the original surface and subsurface material

were examined.

2) The maximum strains associated with the

wear track material are always found at the surface

and the track center. A soft or low dislocation

density zone postulated by the delamination theory

was not found in copper, nor in iron as previously

reported.

3) The strain patterns developed in copper

under dry and under lubricated conditions were

similar; larger strain values were measured after

dry sliding wear.

ACKNOWLEDGEMENTS

The work was partially supported by the Office

of Naval Research and their interest is sincerely

appreciated.

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REFERENCES

1 Scott, D., "Debris Examination - A Prognostic

Approach to Failure Prevention," Wear , Vol. 34, 1975,

pp. 15-22.

2 Seifert, W. W. , and Westcott, V. C., "A

Method for the Study of Wear Particles in Lubricating

Oil," Wear, Vol. 21, 1992

3 Ruff, A. W. , "Characterization of Debris

Particles Recovered from Wearing Systems," Wear , in

press, 1976; see also NBS report 74-474, 1974.

4 Koba, H., and Cook, N. H., "Wear Particle

Formation Mechanisms," ONR report NR229-003, 1974.

5 Scott, D., Seifert, W. W., and Westcott, V. C.,

"Ferrography - An Advanced Design Aid for the 80* s"

Wear , Vol. 34, 1975, pp. 251-260.

6 Suh, N. P., "The Delamination Theory of Wear," Wear,

Vol. 25, 1973, pp. 111-124.

7 Suh, N. P. , Jahanmir, S., Abrahamson, II, E. P.

,

and Turner, A. P. L., "Further Investigation of the

Delamination Theory of Wear," J. Lubr. Tech., Vol. 96,

1974, pp. 631-637.

8 Ruff, A. W. , "Deformation Studies at Sliding

Wear Tracks in Iron," Wear, 40, 59-74 (1976).

9 Stickler, R., Hughes7”*2. W. , and Booker, G. R.,

"Application of the SA-ECD Method to Deformation

Studies," SEM/1971 , IITRI, 1971, pp. 473-480.

10 Spencer, J. P., Booker, G. R. , Joy, D. C., and

Humphreys, C. J., "Electron Channeling Patterns from

Deformed Crystals," SEM/1974, IITRI, 1974, pp. 920-926.

11 Newbury, D. E., "The Origin, Detection and Uses

of Electron Channelling Contrast," SEM/1974, IITRI, 1974,

pp. 1047-1054.

12 Bailey, J. M. , and Gwathmey, A. T., "Friction

and Surface Deformation During Sliding on a Single

Crystal of Copper," ASLE Trans . , Vol. 5, 1962, pp. 45-56.

13 Roshon, Jr., D. D., "Selected Area X-ray

Diffraction Studies of Surface Damage in Sliding on Single-Crystal Copper," J. Appl. Phys., Vol. 35, 1964,

pp. 1262-1269.

14 Wibberley, R., and Eyre, T. S., "The Dry

Sliding Wear Characteristics of Copper with and

without 0.08% Silver," Wear , Vol. 13, 1969, pp. 27-38.

15 Tsuya, Y., "The Behavior of the Layer Damaged

by Friction," Bull. Jap. Soc. Prec. Engg. , Vol. 2,

1967, pp. 214-221.

16 Kirk, J. A., and Swanson, T. D., "Subsurface

Effects During Sliding Wear," Wear, Vol. 35, 1975,

pp. 63-67.

- 9-
17 Bill, R. C., and Wisander, D. W.,

"Recrystallization as a Controlling Process

in the Wear of some FCC Metals," preprint,

1976.

18 Bill, R. C., and Wisander, D. W.

"Surface Recrystallization Theory of the

Wear of Copper in Liquid Methane," NASA

Technical Note TD D-7840, 1974.

19 Swann, P. R., "Dislocation Arrangements

in Face-Centered Cubic Metals and Alloys," in

Electron Microscopy and Strength of Crystals , Interscience, 1963, pp. 131-181.

- 10 -
FIGURE CAPTIONS

Fig. 1 Selected area channeling pattern from

one grain in copper specimen. The 111 band is

marked

.

Fig. 2 SACP from grains in copper strain

calibration specimen (a) C = 7.6%, e = 5.0%

(b) C = 2.3%, e = 27%. The 111 bands are marked

(arrows) and four signal traces are superimposed

on each pattern.

Fig. 3 Strain vs. SACP contrast determined

from calibration specimen.

Fig. 4 Portion of the wear track after 0.17 m

sliding distance in oil. Locations of SACP obtained

are marked.

Fig. 5 SACP from (a) location D and (b) location A in Fig. 4. Band of interest is marked.

Fig. 6 Wear tracks on specimens tested (a)

in oil for 17 m sliding distance and (b) dry for

17 m. Locations at which SACP were obtained on original surface and below surface are marked.

Fig. 7 Strains determined for listed wear

test conditions on original surface at various

distances from track center.

Fig. 8 Strains determined for listed wear

test conditions at indicated depths in specimens

and various distances from track center.

- 11 -
Fig. 1 Selected area channeling pattern from one grain in copper specimen. The 111 band is

marked

WL

BL

(a) (b)

Fig. 2 SACP from grains in copper strain calibration specimen (a) C = 7.6%, e = 5.0% (b) C = 2.3%, e = 27%. The 111 bands are marked

(arrows) and four signal traces are superimposed on each pattern.

- 12 -
Calculated

Strain

(%)

Fig. 3 Strain vs. SACP contrast determined from

calibration specimen.

- 13 -
Fig. 4 Portion of the wear track after 0.17 m

sliding distance in oil. Locations of

SACP obtained are marked.

Fig. 5 SACP from (a) location D and (b) location

A in Fig. 4. Band of interest is marked.

- 14 -
Fig. 6 Wear tracks on specimens tested (a) in oil

for 17 m sliding distance and (b) dry for

17 m. Locations at which SACP were obtained

on original surface and below surface are marked.

- 15 -
Fig. 7 Strains determined for listed wear test

conditions on original surface at various

distances from track center.

Fig. 8 Strains determined for listed wear test

conditions at indicated depths in specimens

and various distances from track center.

- 16 -
QUANTITATIVE METHODS IN WEAR DEBRIS ANALYSIS

A. W. Ruff

Metallurgy Division

National Bureau of Standards

Washington, D.C. 20234

ABSTRACT

Wear debris has been recovered from a number of test systems and analyzed

using different methods. Those methods produced specific information concerning the particulate size and composition. A magnetic debris recovery

method was quantitatively evaluated using actual debris samples and also

using collections of manufactured particulates having known sizes and

compositions. Small 5 pm diameter SiC^ spheres, some containing nickel,

were used to simulate debris. Other particulates of iron and nickel in

different size ranges were also used in order to investigate such matters

as size resolution, lubricant dilution techniques, particle overlap

difficulties, and the general problem of calibration of debris recovery

systems. A comparison between chemical analysis and particulate analysis

findings is presented. The application of optical and electron microscope

methods and X-ray microanalysis in characterizing the wear particulates was

carried out directly on the recovery substrate; those techniques are described.

INTRODUCTION

The characterization of wear debris recovered from operating machines is

frequently conducted for the purpose of evaluating the condition of the

machine [1]. In that way, information additional to that obtained by

chemical analysis of lubricants (SOAP) or through the monitoring of machine

operating parameters can be acquired. Wear debris evaluation can also provide

- 17 -
insight into the operating mechanisms of wear, for example, distinguishing

between adhesive wear and corrosive wear. In recent years, several detailed

studies of wear debris have been reported [2-7]. In those cases, the

authors have described useful techniques for debris recovery and analysis,

and have contributed to an improved understanding of wear. While a few of

the studies reported quantitative data determined from the debris analysis,

much still remains to be done in that regard in order to place wear studies

on a more quantitative basis. Progress in that direction will require

development of more sophisticated (and accurate) measurement methods,

including the means for calibrating those methods. This paper will describe

several experiments involving quantitative comparisons of different debris

analysis methods and some results using simulated debris collections.

EXPERIMENTAL

The wear debris and particulate collections studied here were recovered from

lubricating oil by either of two methods. The first involved filtration

through a perforated membrane filter (Nuclepore^ type) with a pore diameter

about 1 pm. That filter is characterized by a smooth, relatively structurefree surface that introduces a minimum of background detail during subsequent

microscopic examination. After filtering the oil, naptha was passed through

the filter to dissolve any remaining oil and wash the debris that was collected

The filter was then dried at 40 C in a vacuum oven for up to 1 hour, affixed

to a specimen support stub and coated with a conductive layer of carbon in a

vacuum evaporator. The debris could then be examined in place in a scanning

electron microscope (SEM)

1 Nuclepore Corporation. This item is identified here for the purpose of

adequately describing the experimental method used in this study.

- 18 -
2 The second method utilized a magnetic separation process (Ferrography )

that passed a 2 ml volume of oil through a variable gradient magnetic

field arranged so that the debris particles are deposited on a glass

substrate. The particle location in the deposit depends on the particle

magnetic moment (which in turn depends on its size and moment per unit

volume). After preparation and washing in the recommended manner, the

substrate was placed in a vacuum oven at 40 C for up to 1 hour. The

substrate could then be coated with carbon for study in the SEM.

Examination in the SEM was conducted at 20 kV beam potential. Specimen

currents ranged from 100 pA to 100 nA depending on the need to achieve

sufficient x-ray emission intensity for analysis using the energy-dispersive

x-ray detector system. In the x-ray studies, particles of interest were

carefully oriented with respect to the detector in order to achieve good

signal collection and avoid interference effects from neighboring particles.

The particulate collections reported on here consisted of wear debris samples

recovered from turbine engine lubricants and bearing tests , and also several

simulated collections. Porous silica microspheres were obtained"^ in two sizes,

5 ym and 0.7 ym average diameter . Some of the 5 ym spheres were impregnated

with metallic nickel by chemically reducing an absorbed nickel complex. Iron

powder particles of mean diameter 3 ym and nickel particles of 30 ym mean

diameter were also used. Dispersions of the various particulates in automotive

lubricating oil (SAE 30) were produced and then handled as actual oil-debris

samples.

2 Ferrograph, Foxboro/Trans-Sonics , Inc. These items are identified here for

the purpose of adequately describing the experimental method used in this

study.

^The silica sphere samples were provided through the kind cooperation of

J. P. Wolf III and R. K. Iler, E. I. DuPont, Co.

- 19 -
RESULTS AND DISCUSSION

Silica Microspheres

A collection of the nickel -containing SiO^ spheres is shown in Fig. 1.

Some clustering on the A1 substrate is seen as a result of evaporation

of the liquid carrier. The size distribution of the spheres extends from

about 3 ym to 7 ym with an average value of 5 pm. The uniformity of nickel

content was determined by conducting x-ray microanalysis studies on a

collection of spheres. The time required to accumulate 5000 counts of the

Ni-Ka line was measured for each sphere in the collection. The average

count time was 180 sec. with a standard deviation of 40 sec. The combination

of size variation and nickel content variation thus roughly covered a range

of ±50% about the mean value. This was felt to constitute a sufficiently

narrow distribution for the present purpose of evaluating the debris recovery

systems.

An oil sample containing a relatively dilute concentration of the Ni/SiC^

spheres was passed through the magnetic recovery device. An optical micrograph of the resulting debris deposit is shown in Fig. 2a. The initial

deposit volume is located at the upper position in the photograph. Below

the initial deposit, the microspheres occur at a sharply reduced density.

At a suitable concentration in the oil, a collection of uniformly sized

spherical particles of the same composition would (ideally) be expected to

all deposit in the initial volume. Some details on the particle configurations in the deposit are shown in Fig. 2b. The particle strings that form in

the direction of the magnetic field lines start as a single row of the microspheres which increase in size by addition onto the ends. At some later stage

particles attach at the side of the string to begin another row. After two

- 20 -
or more rows form in contact, a second layer can develop on top of the rows,

thus thickening the deposit.

An equal volume mixture of SiO^ and Ni/SiC^ microspheres was prepared and

added to clean oil in order to evaluate the magnetic recovery method with

regard to non-metallic particles. The appearance of the deposit was

essentially that seen in Fig. 2 in that very few Si09 spheres were deposited.

Examination in transmitted light in the optical microscope revealed the nonnickel containing spheres since they transmit some light. The SiC^ spheres

were usually found at random locations on the substrate, not connected to the

strings of nickel -containing spheres (Fig. 3). Clearly the magnetic recovery

method cannot be used if reliable data on non-metallic particle fractions

are desired.

Another mixture was prepared using equal volumes of 5 pm and 0.7 ym nickelSi09 microspheres. An area on the magnetically recovered deposit is

shown in Fig. 4, about 4 mm down from the entry deposit location. The 0.7 ym

spheres are seen to deposit in groups of several spheres. That behavior

probably results from some aglomeration of the spheres during preparation

since single microspheres were rarely seen. Further down the deposit, the

0.7 ym microspheres predominated, still, however, in clustered units.

X-ray microanalysis studies were carried out on several particle strings in

order to determine the uniformity of nickel content in particles of a particular

string. One such group is shown in Fig. 5 and consists of both sizes of

microspheres. The labeled particles were exposed to the incident electron

beam in the SEM under nearly identical conditions of geometry, electron

current density and electron spot size. The Ni-Ka x-ray results are shown

in Table I.

- 21 -
Particles A, B and C are actually clusters of the smaller spheres. The

variation in Ni count rate (proportional to Ni content) for the 5 pm spheres

is due partly to statistical variation (about 6%) and partly to a real

variation in Ni content. The average value of count time is 80 ± 18 sec;

a variation of about 25%. The sample was rotated 180° in the SEM in order

to reanalyze the end particles. The reanalyzed values (1R, 9R) are not

significantly different from the original values indicating that electron

excitation from adjacent particles was not a significant factor in producing

the different count times for these two microspheres (numbers 1 and 9)

The effect of particle size and electron beam penetration on x-ray emission

has previously been studied for iron - 3% silicon particles [7]. It was

shown there that the x-ray emission intensity decreased rapidly for particle

sizes below about 3 pm. That same size effect would be expected for nickel

particles. Thus the size variation found among the 5 ym spheres does not

require any correction, however, any comparison with the smaller 0.7 ym

microspheres requires adjustment. The relative emission factor [7] at that

size is about 0.3 so that the corrected count time values for clusters A and

C is about (0.3) (350) = 100 sec. That value is reasonably consistent with

the Ni-Ka count time values for the larger microspheres as given above.

Other Particulate Mixtures

A mixture of irregularly shaped 3 ym Fe particles and the 5 ym Si02 microspheres

was prepared to further examine the differentiation of the magnetic recovery

method for metallic and non-metallic mixtures. Equal volumes of the dry powders

were added to clean lubricating oil. One sample was filtered through a 1 ym

pore sized filter; the result is shown in Fig. 6a where the irregularly

shaped particles are iron. The equi-volume initial proportion is consistant

- 22 -
with the appearance of this filter deposit. Another portion of the same

oil sample was passed through the magnetic recovery system; the resulting

deposit is shown in Fig. 6b. Only a very small fraction of non-metallic

particles were recovered.

Another mixture of two types of metallic particulates consisted of an

equal volume of 30 ym Ni particles and 3 ym Fe particles dispersed in

lubricating oil. A deposit of that mixture that was magnetically recovered

is shown in Fig. 7. The entry deposit region contained nearly all of the

larger Ni particles (at the solids concentration used here), however, many

of the smaller particles were also found at the entry volume. The smaller

particles appear to deposit there as a result of locally high field strengths

adjacent to the larger debris particles. Further down the deposit where the

imposed magnetic field gradient is larger only the smaller 3 ym particles

were found.

Oil Dilution Studies

The effect of different solids concentration in the oil on the quantitative

recovery of debris was examined. In one experiment, a deposit of wear debris

obtained from a jet engine lubrication system was recovered using the magnetic

method. The deposit was characterized. It was then washed free from the

substrate (using oil) and added to fresh oil of sufficient volume to obtain

1/5 the original concentration. That dilute sample was passed through the

magnetic recovery system and analyzed with the results shown in Table II (the

samples are designated K9 and 1/5 :K9, respectively). The initial deposit

height was measured using a calibrated fine focus control on an optical

microscope. The initial deposit volume was calculated after microscopic

- 23 -
measurement. The relative area coverages were determined using photoelectric measurement of light transmission through the deposit at the

indicated locations (measured from the initial deposit as origin) . Those

values do not represent absolute densities of the deposit. Examination of

the results in Table II shows that the initial deposit volume ratio (6.6)

and the coverage ratios (6.3 and 7.1) at the 1 mm and 5 mm location are

comparable to the known debris concentration ratio (5.0). On the other

hand, the initial deposit height and the relative coverage at the entry

deposit do not change in proportion to the debris concentration and would

be less satisfactory quantitative measures.

A second specimen was evaluated before and after a 10:1 dilution. The

particulates in that set were 5 ym Ni/Si02 microspheres. As shown in

Table II only the initial deposit volume ratio (11) and the area coverage

ratio at 1 ym location (8.3) are comparable to the known particle concentra

tion ratio (10). It is concluded that those two measures can be used with

the most confidence in quantitative characterization of magnetically

recovered debris.

Analytical Method Comparison

A sample of oil was obtained from a laboratory test of a tapered roller

bearing. The sample was taken immediately prior to failure of that bearing

Spectrometric oil analysis readings had been obtained on this sample as

well as on others periodically through the test duration. Wear debris

samples had also been obtained periodically. The trends of those two

measures of wear rate have been compared [8]; the interest here is with

the last oil sample. The spectrometric reading was obtained at a SOAP

- 24 -
laboratory using conventional methods and indicated 6 ppm Fe. That

same oil was further divided into two 1 g samples and analyzed here by

wet chemical methods. That procedure indicated an iron content of 3.7

and 4.0 ppm, or an average of 3.8 ppm Fe. The spectrometric value is

about 50% larger for this sample and appears to be inaccurate by that

amount. Two other 2 ml samples were drawn from the same oil and passed

through the magnetic recovery system to produce two debris deposits. The

initial deposit volume was stripped from each slide using plastic

replicating tape and subsequently analyzed by wet chemical methods. The

two values obtained for iron particulate content in the initial deposit

volume were 0.7 and 0.8 ppm Fe. The remaining debris particles on the

slide (located below the initial deposit) were removed and found to total

0.8 and 1.1 ppm Fe. Thus the recovered debris particles totaled an average

of 1.7 ppm Fe, with approximately 50% in the larger size group (3 to 50 pm,

entry volume) and 50% in the smaller group (<2 pm). Clearly that ratio will

depend on the debris size distribution and other factors. Of more interest

here is the total particulate analysis of 1.7 ppm Fe which is only approximately 50% of the total iron content (3.8 ppm) found in the oil by analysis.

Apparently, a large portion of the iron content occurs in extremely small

particles that are not magnetically recovered or as a dissolved constituent.

Further investigation is needed into this matter of wear product distribution

within lubricants and into the comparison of methods of recovery and analysis.

SUMMARY

Experiments have been conducted on various types of actual and simulated wear

debris particles recovered from lubricating oil using either filtration or

magnetic deposition methods. Both spherical and randomly shaped particles

were used in the size range 0.7 pm and 50 pm. The filter method cannot

-25-
discriminate between metallic and non-metallic particles. That feature

is a disadvantage when the wear debris may be obscured by irrelevant

contaminants such as carbon deposits, however, it would be an advantage

in terms of recovering significant abrasives from the lubricant. The

magnetic gradient method reliably recovers metallic debris and offers the

advantage of additionally classifying the particles with regard to

material type and size. That classification feature can probably be

calibrated in a reasonably quantitative manner. The magnetic method cannot

reliably recover non-metallic debris. Quantitative analysis methods can be

carried out on the particle-substrate combination resulting from either

method of debris recovery.

ACKNOWLEDGEMENTS

This work was partially supported by the Naval Air Engineering Center,

Lakehurst, New Jersey. The contribution of oil samples and valuable

information and discussion by H. Dalai, V. Westcott and co-workers is

gratefully acknowledged.
Particles 1 2 3 4 5 6 7 8 9 A B C 1R 9R

Time for

lO^ counts

(sec.

)

108 87 79 70 77 104 76 60 58 350 112 360 99 53

Table I. X-ray microanalysis results on particles identified in Fig. 5.

Sample Initial Deposit

Relative Area Coverage

at Indicated Location

Volume (pm3) Height (pm) Entry 1mm 5mm

K9 6.6 x loj? 65 36 14 * 5 1/5 :K9* 1.0 x 10° 24 11 2.2 0.7

ratio 6.6 2.8 3.3 6.3 7.1

NBS-7 1.2 x 10

6

. 23 14 5 0.6

1/10 :NBS-7 0.11 x 10° 12 2.5 0.6 —

ratio 11 2.0 5.6 8.3 —

*Particles were washed from original deposit.

Table II. Magnetic Recovery System - Dilution Effects on Performance

- 27 -
FIGURE CAPTIONS

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

- Nickel -containing SiO ? microspheres; average diameter 5 ym.

- Deposit of nickel -containing Si02 spheres, (a) Initial deposit

at upper end. (b) Details of particle arrangements in groups.

- Equal volume mixture of 5 ym Si02 spheres and Ni/Si02 spheres

after magnetic separation. Details near edge of deposit.

spheres are marked.

- Group of particles from mixture of 5 ym and 0.7 ym Ni/SK^ spheres.

- Group of 0.7 ym and 5 ym Ni/Si02 spheres used in x-ray microanalysis study.

- (a) Oil sample containing equal volume mixture of 5 ym Si02 spheres

and 3 ym Fe particles, filtered through 1 ym pore sized filter,

(b) Magnetic separation deposit from above mixture. Four

spheres are seen in this region.

- Magnetic separation deposit of a mixture of 30 ym Ni particles and

3 ym Fe particles. Entry deposit region contains all large

particles and some small particles.

- 28 -
REFERENCES

1. Scott, D., "Debris Examination - A Prognostic Approach to Failure

Prevention," Wear 34 (1975) 15-22.

2. Seifert, W. W. , and Westcott, V. C., "A Method for the Study of Wear

Particles in Lubricating Oil," Wear 21 (1972) 27-42.

3. Westcott, V. C., and Seifert, W. W. , "Investigation of Iron Content of

Lubricating Oil using a Ferrograph and an Emission Spectrometer,"

Wear 23 (1973) 239-249.

4. Koba, H. , and Cook, N. H., "Wear Particle Formation Mechanisms," ONR

report NR229-003 (1974).

5. Jones, W. R. , "Ferrographic Analysis of Wear Debris from Boundary

Lubrication Experiments with Five Ring Polyphenylether ," ASLE Trans.

18 (1975) 153-162.

6. Scott, D. , Seifert, W. W. , and Westcott, V. C., "Ferrography - An

Advanced Design Aid for the 80's," Wear 34 (1975) 251-260.

7. Ruff, A. W. , "Characterization of Debris Particles Recovered from

Wearing Systems," Wear, in press (1976); see also NBS report

74-474 (1974).

8. Westcott, V. C., private communication.

- 29 -
- 30 -
to0 • p C/> 0

-C §• a o

to P

too <N1 • O x)

•H

C -H

CO 0

to

b0 P P C 0 C

•H cx 0

CX 6 •(“( D 0

aj bo P P c P Ctj TO O P U P P i • r-1

CtJ t—H

to 0 o 0

fXi—1 u 0 U

•H XJ •H c P

rH P

Mh 05 rf o •H P, P P •H M-t

•fH £ o

to i—i o to CX 1—t 0 •H Q "a? w ctl +j0 • Q CNJ

ci

•H

PU - 31 -
Fig. 3. Equal volume mixture of 5/Am SiCL spheres and Ni/SiCL spheres after

magnetic separation. Details near edge of deposit. SiC^ spheres are marked.

Fig. 4. Group of particles from mixture of 5 pm and 0.7 pm Ni/SiC>

2 spheres.

- 32 -
Fig. 5. Group of 0.7 pm and 5 pm Ni/SiC^

spheres used in x-ray microanalysis study.

- 33-
Fig. 6. (a) Oil sample containing equal volume mixture of 5 pi SiO? spheres and 3 pm Fe particles, filtered through 1 pm pore sized filter.

_ (b) Magnetic separation deposit from above

mixture. Four SiO^ spheres are seen in this region.

- 34 -
Fig. 7. Magnetic separation deposit of a mixture of 30 pm

Ni particles and 3 pm Fe particles. Entry deposit region

contains all large particles and some small particles.

- 35 -
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Cruiser Destroyer Force

Pacific Fleet

Code 434

San Diego, California 92110

Attn: Chief Collins 1

Commanding Officer

Naval Ordnance Systems Support Office, Atlantic

Building #62

Norfolk Naval Shipyard

Portsmouth, VA 23709

Attn: J. Reidy 1

Commanding Officer

Naval Ordnance Systems Support Office, Pacific

Post Office Box 80548

San Diego, California 92138

Attn: Code 081 Clay Westfall 1

Commanding Officer

Naval Ship Engineering Center

Code 6101F

Prince George’s Center

Hyattsville, Maryland 20782

Attn: E. C. Davis 1

Commanding Officer

Naval Air Rework Facility

Technical Support Center (Code 360)

Naval Air Station

Pensacola, FLA 32508

Attn: R. Purcell 1

Commander

Charleston Naval Shipyard

Metals Section

Material Laboratory (Code 134.11)

Charleston, S.C. 29408

Attn: Hillary Douglas 1

- 45 -
Commander

Naval Ship Repair Facility

Subic

FPO San Francisco 96612 1

Commander

Naval Ship Repair Facility

Guam

FPO San Francisco 96612 1

Department of Chemistry

University of North Carolina

Chapel Hill, N.C. 27514

Attn: Dr. T. Isenhower 1

Assistant Chief for Technology

Office of Naval Research, Code 200

Arlington, Virginia 22217 1

Prof. R. M. Latanision

Metallurgy Dept., 8-202

MIT

Cambridge, Mass. 02139 1

Mr. V. C. Westcott

Trans Sonics, Inc.

P. 0. Box 326

Lexington, Massachusetts 02713 1

Dr. Ranga Komanduri

Camegie-Mellon University

Mechanical Engineering

Pittsburgh, PA 15213 1

Dr. Robert I. Jaffee

Technical Manager, Materials

Electric Power Research Institute

3412 Hillview Avenue

P. 0. Box 10412

Palo Alto, CA 94304 1

Dr. Bernard H. Kear

Materials Engineering and Research Laboratory

Pratt § Whitney Aircraft

Middletown Plant

Middletown, Connecticut 06457 1

- 46 -
Dr. F. S. Pettit

Materials Engineering § Research Laboratory

Pratt § Whitney Aircraft

Middletown Plant

Middletown, Connecticut 06457 1

Dr. B. A. Wilcox

Division of Materials Research

National Science Foundation

1800 G Street

Washington, D.C. 20550 1

Dr. I. G. Wright

Metal Science Section

Battelle Columbus Laboratories

505 King Avenue

Columbus, Ohio 43201 1

Prof. I. Finnie

Dept, of Mechanical Engineering

University of California

Berkeley, CA 94720 1

Dr. Edward Van Reuth

ARPA

1400 Wilson Blvd

Arlington, VA 22209 1

Dr. E. Saibel

Army Research Office

P. 0. Box 1221

RTP, North Carolina 27709 1

Prof. David A. Rigney

Dept, of Metallurgical Engineering

The Ohio State University

116 West 19th Avenue

Columbus, Ohio 43210 1

- 47 -
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OK REPORT NO. NBSIR - 1141

2. Gov't Accession

No.

3. Recipient’s Accession No. AD AO 31530

4. TITLF. AND SUBTITLE

Study of Initial Stages of Wear by Electron Channeling

I. measurement of Plastic Strain in Copper Due to

Sliding Wear

II. Quantitative Methods in Wear Debris Analysis

5. Publication Date October 1976

6. Performing Organization Code

7. AUTHOR(S)

A. W. Ruff

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 3120438

11. Contract/Grant No. N00014-76-F-002

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Department of the Navy

Office of Naval Research

Arlington, VA 22217

13. Type of Report & Period Covered

Final Report

14. Sponsoring Agency Code

15.

SUPPLEMENTARY NOTES

16.

ABSTRACT (A 200-word or less (actual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Wear experiments have been conducted to determine the plastic strains that are introduced in the surface material near sliding wear tracks. Both oil lubricated and

dry sliding experiments have been carried out at different sliding distances on sur- faces of copper. The strain values were determined from selected area electron channel

ing patterns obtained using a scanning electron microscope from regions as small as

10 ym in size and 0.05 ym deep around the wear track. A deformed calibration specimen

was used to relate electron channeling band contrast to deformation strain. Strain

maps were obtained on the wear surface lateral to the wear track and also below the

surface using electropolishing metal removal techniques. Particular attention was placed on the near-surface strain values. In all cases, the maximum strain was found

at the wear surface located at the track center and the strains decreased uniformly

with depth. Significant, large strains were also found outside the wear tracks. The

results are compared with those previously reported for iron and with recent

theoretical models.

Wear debris has been removed from a number of test systems and analyzed using

different methods. Those methods produced specific information concerning the

particulate size and composition. A magnetic debris recovery method was quantitatively

evaluated using actual debris samples and also using collections of manufactured

(CONTINUED ON ATTACHED)

17.

KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Copper; electron channeling; electron microscope; metals; particle analysis;

plastic deformation; surfaces; wear; wear debris; x-ray analysis.

18. AVAILABILITY foci Uni imited

[33 F°( Official Distribution. Do Not Release to NTIS

Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. Cl 3 3 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

22. Price

U SCOMM- DC 29042-P74
NBS-1 1 4A (REV. 7-7 3)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR RKPORT NO. NBSIR-1141 Continued2. Gov’t Accession

No.

3. Recipient’s Accession No. AD AO 31530

4. TITLE AND SUBTITLE 5. Publication Date

6. Performing Organization Code

7. A UTHOR(S) 8 . Perfor ming Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

1 1 . Contract/Gr ant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less (actual summary of most si frifi cant information. If document includes a significant

bibliography or literature survey, mention it here.)

particulates having known sizes and compositions. Small 5 ym diameter Si02 spheres,

some containing nickel, were used to simulate debris. Other particulates of iron and

nickel in different size ranges were also used in order to investigate such matters

as size resolution, lubricant dilution techniques, particle overlap difficulties, and

the general problem of calibration of debris recovery systems. A comparison between

chemical analysis and particulate analysis findings is presented. The application

of optical and electron microscope methods and x-ray microanalysis in characterizing

the wear particulates was carried out directly on the recovery substrate; those

techniques are described.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

18. AVAILABILITY Unlimited

1

' For Official Distribution. Do Not Release to NTIS

1 Order From Sup. of Doc., U.S. Government Printing Office Washington, D.C. 20402, SD Cat. No. 03

| | Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

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USCOMM-DC 2 904 2- P 7 4

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