Abrasive tool for honing

The ratio of stock removal to tool wear (G ratio) of an abrasive tool having a copper-tin bond alloy with diamond abrasive grit dispersed therein is more than doubled when honing cast iron by including titanium carbide particulate in the bond alloy in an amount of about 0.5 weight percent to less than 20 weight percent, preferably from about 1 to 5 weight percent, based on the total weight of copper and tin.

FIELD OF THE INVENTION 
The present invention relates to abrasive tools useful for honing and 
sizing workparts. 
BACKGROUND OF THE INVENTION 
Metal bonded abrasive tools for honing bores in workparts are known in the 
art. For example, a metal bonded diamond tool is disclosed in U.S. Pat. 
No. 3,594,141 issued July 20, 1971 to Houston et al. The tool is described 
as including a backing element made of iron and bronze (copper-tin) 
sintered powder and a stone element thereon. The stone element comprises a 
bond or matrix alloy which is a sintered mixture of cobalt and tungsten 
carbide powders with other refractory carbides such as titanium carbide, 
chromium carbide, tantalum carbide or vanadium carbide optionally present 
and further comprises diamond grits held in the bond alloy. The ratio of 
carbide to cobalt in the bond alloy is varied from 20 weight percent to 90 
weight percent inversely with cobalt from 80 weight percent to 10 weight 
percent in the bond alloy. The honing tool is subjected to a two stage 
sintering treatment such that the bronze component of the backing element 
is caused to liquify and infiltrate the matrix of the stone element. Upon 
cooling, the bronze infiltrant solidifies in the matrix of cobalt and 
tungsten and other carbides, occupying about 30% of the volume of the 
stone element. 
U.S. Pat. No. 4,142,872 issued Mar. 6, 1979 to Conradi also describes a 
metal bonded abrasive tool which comprises a bonding matrix of sintered 
borided cobalt powder with optional fillers such as tungsten carbide, and 
diamond or cubic boron nitride abrasive particles held in the bonding 
matrix. The cobalt powder and abrasive particles are sintered together 
with the boriding of the cobalt being conducted prior to or during the 
sintering treatment. 
U.S. Pat. No. 3,496,682 issued Feb. 24, 1970 to Quaas et al. describes a 
flame sprayable alloy composition for producing cutting and/or wear 
surfaces on substrates. The flame sprayable composition includes a matrix 
system of nickel, cobalt or copper base and diamond abrasive bort 
entrapped in the matrix as the composition is sprayed on the substrate. 
Refractory carbides such as tungsten, titanium, chromium, zirconium and 
molybdenum carbides may be mixed with the diamond bort in an amount of 1 
to 50 percent by weight. The matrix system must melt below 2400.degree. F. 
and to this end nickel base alloys, cobalt base alloys and copper base 
alloys of the copper-silicon and copper-tin type are employed. 
Other abrasive tools or articles are disclosed in U.S. Pat. No. 3,596,649 
issued Aug. 3, 1971 to Olivieri, U.S. Pat. No. 4,308,035 issued Dec. 29, 
1981 to Danilova et al. and U.S. Pat. No. 4,311,490 issued Jan. 19, 1982 
to Bovenkerk et al. Methods for producing abrasive articles or individual 
abrasive grains are illustrated in U.S. Pat. No. 3,389,981 issued June 24, 
1968 to Strauss, U.S. Pat. No. 3,785,938 issued Jan. 15, 1974 to Sam, U.S. 
Pat. No. 4,024,675 issued May 24, 1977 to Vladimicrovich et al. and U.S. 
Pat. No. 4,184,853 issued Jan. 22, 1980 to Otopkvov et al. 
SUMMARY OF THE INVENTION 
In a typical working embodiment, the present invention provides an abrasive 
tool comprising a metal bond alloy or matrix of copper, tin and optionally 
cobalt in which titanium carbide particulate is included in an amount from 
about 0.5 weight percent but less than 20 weight percent, preferably about 
0.5 to 10 weight percent, and even more preferably about 1 to 5 weight 
percent based on the total metal alloy weight to significantly increase 
the G ratio (i.e., ratio of stock removal to tool wear) during honing. 
Diamond and/or cubic boron nitride abrasive grit is also held in the bond 
alloy.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Abrasive tools of the invention include a copper-tin or copper-tin-cobalt 
bond alloy or matrix to which is added titanium carbide in critical 
amounts. Abrasive grit in the form of diamond and/or cubic boron nitride 
particulate is held in the bond alloy. The Table hereinbelow sets forth 
the composition of the bond alloy for certain abrasive tools which were 
subjected to honing tests of cast iron as described in detail below. The 
tools represented in the Table each had diamond particulate dispersed 
throughout the bond alloy along with the titanium carbide particulate, the 
diamond being present in an amount of 100 concentration (or about 25% by 
volume of the tool being diamond particulate). 
TABLE 
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Bond Alloys 
Tool # Cu Sn Co Ag TiC 
______________________________________ 
10 73.5 26.5 -- -- 0 
11 71.0 24.0 -- -- 5 
12 68.5 21.5 -- -- 10 
13 63.5 16.5 -- -- 20 
20 34 13 48 5 0 
21 34 13 47 5 1 
22 34 13 43 5 5 
______________________________________ 
Tool #'s 10 and 20 are reference tools against which the honing capability 
of the other tools is compared and they are not considered part of the 
present invention. 
The tools were made by conventional hot pressing procedures, including a 
mixing step, cold compaction step and hot compaction step. In particular, 
the process for making the tools consisted of the following detailed 
steps: 
(a) The elemental metallic powders, TiC powder and diamond particulate were 
measured out and tumble mixed in a conventional drum mixer for 24 hours. 
The metallic powders had a particle size of minus 325 mesh while the TiC 
and diamond particulate had a particle size of minus 325 mesh and 140/170 
mesh, respectively. 
(b) A conventional high speed steel (T-1) die with a rectangular cavity and 
having a punch was filled with the appropriate amount of powder premixed 
in step (a). 
(c) The powder was cold compacted in the die at 10 TSI (tons per square 
inch) in a conventional hydraulic press. 
(d) The punch/die assembly with cold compacted powder therein was placed in 
a furnace having a nitrogen or other inert atmosphere and heated to about 
1325.degree. F. for 1 hour. 
(e) The heated punch/die assembly was removed from the furnace and 
immediately compacted at a sufficient punch pressure to compact the powder 
to a density of 8.60 g/ml. 
(f) After hot compaction, the punch/die assembly is air cooled to room 
temperature under punch pressure in the press. 
(g) Then, the room temperature assembly is removed from the press and the 
compacted powder tool is removed. 
(h) The compacted tool is then ground true and to size if necessary. 
The honing tools thus made were tested in laboratory honing experiments as 
follows: 
Cylindrical specimens of cast iron simulating engine block cast iron were 
provided in 6-inch lengths with a 31/2 inch diameter bore therethrough. 
Honing tests were performed on a Model #728 honing machine manufactured by 
Micromatic Division of Ex-Cell-O Corporation, Troy, Mich. Prior to honing, 
the long dimension of the rectangular stones was measured to .+-.0.0001 
inch and the specimen bore was measured to .+-.0.0005 inch. For honing, 
the Microdial.RTM. stone expander adjustment mechanism on the machine was 
set to expand or feed out the stones 0.018 inch in 6 minutes at a spindle 
speed of 360 RPM and reciprocation of 60 cycles/minute (one cycle=stone 
insertion pass and stone withdrawal pass). The honing tools were initially 
run in the specimen bore until the stones were satisfactorily seated. The 
actual honing test consisted of 5 travels of the Microdial stone expander, 
i.e., the stones were expanded 0.018 inch over 6 minutes five different 
times under the spindle speed and reciprocation conditions noted above. 
Thereafter, stone wear was measured to 0.0001 inch and specimen bore 
diameter was measured to 0.0005 inch after the tool and specimen were 
allowed to cool to room temperature. From the stone wear and specimen bore 
diameter changes, the ratio of cubic inches of stock (specimen) removal to 
cubic inches of stone wear (the well-known "G" ratio) was calculated. 
The results of these tests are shown in the FIGURE which is a bar graph 
depicting abrasive loss per cycle of the honing process for each tool 
made. 
It is apparent that addition of titanium carbide to the copper-tin bond 
alloy of tool #10 had a beneficial effect when titanium carbide additions 
are limited to less than 20.sup.w /o. When the weight percent of titanium 
carbide was 5.sup.w /o and 10.sup.w /o, special beneficial effects were 
noted. For example, when 5.sup.w /o titanium carbide was added, abrasive 
loss per cycle decreased from over 0.0004 for tool #10 to less than 0.0002 
for tool #11 representing an increase in G ratio from 7,477.7 to 29,926.8. 
When 10.sup.w /o titanium carbide was added, abrasive loss per cycle 
decreased from over 0.0004 to less than 0.0003 for tool #12 (increase in G 
ratio from 7,477.7 to 14,955.4) but was nevertheless higher than abrasive 
loss for tool #11 with 5.sup.w /o titanium carbide. Tool #13 illustrates 
that titanium carbide must be limited to less than 20 weight percent to 
avoid an unacceptable increase in abrasive loss per cycle. 
The beneficial effect of titanium carbide additions to the tools with 
copper-tin-cobalt-silver bond alloys is also illustrated in the FIGURE. 
For example, the addition of 1.sup.w /o titanium carbide results in a 
decrease in abrasive loss from over 0.0002 for tool #20 to less than 
0.0002 for tool #21 representing an increase in G ratio from 832.1 to 
1869.4. Tool #22 with 5.sup.w /o titanium carbide illustrates decreased 
abrasive loss per cycle but slightly higher than tool #21. 
In these tests, it is apparent that tool #11 was substantially equivalent 
to tool #21 and tool #22. Since the latter tools contain substantial 
amounts of expensive cobalt and silver, tool #11 appears to offer a much 
lower cost alternative in some applications, at least involving honing of 
cast iron. Of course, honing of other materials such as hard steel may 
produce different results. In fact, honing of hard steel fuel nozzles 
showed tool #11 to be inferior to tools #20 and #21. 
Abrasive tools of the present invention should have from about 0.5 to less 
than 20 weight percent titanium carbide dispersed in the bond alloy. 
Preferably, titanium carbide is present in amounts from about 1 to about 
10 weight percent and, even more preferably from about 1 to about 5 weight 
percent based on total weight of the metal bond alloy (Cu-Sn or 
Cu-Sn-Co-Ag). These titanium carbide additions can made to various metal 
bond alloy compositions, a preferred metal alloy bond consisting 
essentially of from about 10 to 90 weight copper, 10-30 weight tin, up to 
about 50 weight percent cobalt and up to about 10 weight percent silver. 
A particularly preferred metal bond alloy would have from about 70 to 80 
weight percent copper and about 20 to 30 weight percent tin with titanium 
carbide present from about 1 to 5 weight percent based on total weight of 
copper and tin. 
Another particularly preferred metal bond alloy would have about 20 to 30 
weight percent copper, about 10 to 20 weight percent tin, about 40 to 50 
weight percent cobalt and up to about 10 weight percent silver with 
titanium carbide present from about 1 to 5 weight percent based on the 
total weight of the metallic bond components. 
Of course, in the above embodiments, cubic boron nitride could be used in 
lieu of the diamond particulate as the abrasive grit depending upon the 
material being honed and other sizes of particulate could be used. 
Although the invention has been illustrated with respect to specific 
examples and preferred embodiments, it will be understood by those skilled 
in the art that various changes may be made therein within the scope of 
the appended claims which are intended to also include equivalents of such 
embodiments.