Cermet alloy containing nitrogen

A cermet alloy and a drill formed of the cermet alloy include hard dispersed phases and binder metal phases. The hard dispersed phases include a metal atom group containing titanium and a nonmetal atom group containing nitrogen. The amount of titanium contained in the metal atom group is at least 0.5 and not more than 0.95 as an atomic ratio. The amount of nitrogen contained in the nonmetal atom group is at least 0.1 and not more than 0.7 as an atomic ratio. The hard dispersed phases further include a fine grained portion having a mean grain size of at least 0.2 .mu.m and not more than 0.6 .mu.m and a coarse grained portion having a mean grain size of at least 1 .mu.m and not more than 3 .mu.m. The volume ratio of the fine grained portion to the course grained portion is at least 0.3 and not more than 3. The proportion of the binder metal phases contained in the cermet is at least 5 percent by weight and not more than 30 percent by weight. This cermet drill has an excellent wear resistance, toughness and thermal cracking resistance.

FIELD OF THE INVENTION 
The present invention relates to a high-quality cermet alloy containing 
nitrogen which has an excellent wear resistance and toughness and is 
capable of withstanding high-speed cutting. The invention also relates to 
a drill which is formed of such a cermet alloy. The term "drill" as used 
herein refers to a drill bit. 
Background Information 
A drill is a cutting tool which is employed for drilling holes into a 
workpiece of steel or the like. FIG. 1 shows the structure of a twist 
drill by way of example. The twist drill generally comprises a head 
portion 1 which is adapted to cutting, and a shank portion 2 which is not 
much concerned with the cutting but is mainly adapted to discharge chips 
as well as to mount the drill in a chuck of a cutting machine such as a 
drilling machine. 
In a working condition, the head portion and the shank portion of a drill 
are subject to different conditions. Therefore, characteristics required 
for the respective portions of the drill are different from each other. 
For example, wear resistance and deposition resistance etc. are required 
for a cutting edge part of the head portion, while toughness for 
maintaining strength of the tool is required for the shank portion. Also, 
different portions of the cutting edge part of the head portion must have 
different characteristics because the central cutting edge portion and the 
outer peripheral cutting edge portion are subject to vary different in 
cutting speeds. In order to satisfy such complicated requirements, various 
materials have hitherto been developed for drills. 
Up to this time, general materials for drills are high-speed steel and 
cemented carbide. High-speed steel, which is superior in toughness but 
inferior in wear resistance, is improper for high-speed cutting. On the 
other hand, cemented carbide, which has an excellent wear resistance and 
cutting accuracy but is brittle, may be bent when used in a machine tool 
having low rigidity, for example. 
In order to improve the above situation, a drill structure with a head 
portion of high-speed steel coated with hard TiN, or a structure with a 
head portion made of cemented carbide and brazing the same has been 
considered. However, the head portion subjected to coating has had such a 
disadvantage that a coating layer of at least its front flank side is 
removed when regrinding of the drill and the greater part of the effect of 
coating is lost. Further, the structure formed by brazing the head portion 
with cemented carbide has had such a disadvantage that the same cannot be 
used for cutting a hard to cut material; nor for deep hole drilling since 
brazing itself is essentially inferior in thermal strength and mechanical 
strength. 
In recent years there have been proposed a structure of brazing different 
materials (P30 and D30) of cemented carbide, see Japanese Utility Model 
Laying-Open No. 58-143115, and a structure of metallurgically integrating 
or joining the same, see Japanese Utility Model Publication No. 62-46489 
for attaining improvements in wear resistance and toughness. The 
difference between characteristics required for a central part and an 
outer peripheral part of a drill and making materials of cemented carbide 
for the central part and for the outer peripheral part to differ from each 
other to form a double structure, have been described in Japanese Patent 
Laying-Open No. 62-218010. Methods of forming this double structure by 
injection molding have been described in Japanese Patent Laying-Open Nos. 
63-38501 and 38502. In addition, preparing the material for a drill from 
cermet, in order to improve the deposition resistance of the drill is 
described in Japanese Patent Laying-Open No. 62-292307 or the like. In 
these conventional examples, those preparing cemented carbide from coarse 
grains and bringing the same into strong binder phases for the purpose of 
improving the toughness of the shank portions of the drills, have 
unintendedly reduced strength of the materials or are subject to elastic 
change or distortion, which cause such a problem that the drills are bent 
during drilling by vibration of the workpieces, by instable rotation of 
the drilling machines or the like. 
Thus, improvements have hitherto been made based on individual viewpoints, 
with respect to complicated requirements for drills. However, none of 
these conventional structures have completely satisfied the requirements 
for the overall characteristics of the drills. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a cermet alloy 
containing nitrogen, which has an excellent performance characteristic 
particularly in its wear resistance and toughness. 
Another object of the present invention is to provide a cermet drill formed 
of cermet, which has excellent wear resistance and deposition resistance 
in a head portion of the drill, while having the necessary and sufficient 
characteristics in its shank portion. 
Still another object of the present invention is to provide a drill of a 
sintered hard alloy formed of WC cemented carbide, which has an excellent 
wear resistance and deposition resistance in a head portion of the drill 
while having the necessary and sufficient characteristics in its shank 
portion. 
The invention's purpose is to improve the wear resistance and deposition 
resistance in particular, among the characteristics required for a drill. 
It has been found to be necessary to employ cermet containing nitrogen, 
which is mainly composed of titanium (Ti), in order to improve the wear 
resistance and the deposition resitance. To this end, parametric 
experiments have been made with respect to various components contained in 
cermet. A number of effective features have been found. 
A first drill embodiment has the following features: 
(1) Hard dispersed phases of cermet have mixed structures of finely 
classified fine-grain hard phases with a grain size of 0.2 to 0.6 .mu.m 
and coarse-grain hard phases with a grain size of 1 to 3 .mu.m. The volume 
mixing ratio of the fine-grain hard phases to the coarse-grain hard phases 
is 0.3 to 3.0. Within this range, it is possible to effectively suppress 
the generation and progress of cracking caused by a thermal shock which is 
applied to the cutting edge of the drill when the drill is used. More 
preferably, the grain sizes of the fine-grain hard phases are 0.3 to 0.5 
.mu.m and the grain sizes of the coarse-grain hard phases are 1.5 to 2.2 
.mu.m. 
(2) The hard dispersed phases of the cermet are composed of a nitride of 
titanium carbonitride compound of titanium and at least one metal selected 
from the groups IVa, Va and VIa of the periodic table excluding titanium, 
and the composition of the hard dispersed phases is such that the titanium 
content in metal atoms is 0.5 to 0.95 as an atomic ratio. Wear resistance 
and deposition resistance of cermet are rendered insufficient if the 
titanium content is less than 0.5. If the titanium content exceeds 0.95, 
on the other hand, the degree of sintering of cermet is deteriorated. 
(3) The proportion of nitrogen in nonmetal atoms contained in the hard 
dispersed phases is 0.1 to 0.7 as an atomic ratio. Namely, an effect 
whereby nitrogen suppresses the grain growth of the hard dispersed phases 
during sintering, is not attained if the proportion of nitrogen is less 
than 0.1 as an atomic ratio. If the nitrogen ratio exceeds 0.7, on the 
other hand, the degree of sintering the cermet deteriorates. 
(4) The amount of binder metal phases contained in the cermet is 5 percent 
by weight to 30 percent by weight. If it is less than 5 percent by weight, 
the toughness of cermet is rendered so insufficient that chipping is 
caused when the drill is used. If the binder exceeds 30 percent by weight, 
on the other hand, the wear resistance is rendered so insufficient that 
significant wear is caused in a flank of the cutting edge or a margin part 
of the drill. 
In a second embodiment of the invention the drill has the following 
features: 
(1) In order to suppress the generation and progress of cracking which is 
caused by a thermal shock at the cutting edge of the drill, the volume 
mixing ratio of fine-grain hard phases with a grain size of 0.2 to 0.6 
.mu.m to coarse-grain hard phases with a grain size of 1 to 3 .mu.m must 
be in a range of 0.3 to 3.0. More preferably, the grain sizes of the 
fine-grain hard phases are 0.3 to 0.5 .mu.m, and the grain sizes of the 
coarse-grain hard phases are 1.5 to 2.2 .mu.m. 
(2) In order to increase the toughness and strength required for drill 
shank portion, the hard dispersed phases of cermet must be fine grained 
structures with a grain size of 0.2 to 0.6 .mu.m. The aforementioned two 
cermet materials are similar in composition to each other, although the 
same are different in characteristic from each other. Thus, it is possible 
to continuously join and form these materials without employing a 
discontinuous and low-strength joining method such as brazing. An example 
of such a joining method is the press (dry bag) time junction, HIP time 
junction or the like. 
According to the invention, a head portion and a shank portion of a drill, 
which are formed of a different compositions of cermet materials, are 
integrally joined with each other. The composition of each part of this 
drill and characteristics thereof will now be described. 
I. HEAD PORTION 
A. Components of Hard Dispersed Phases 
a. The hard dispersed phases are composed of a nitride compound of titanium 
or a carbo-nitride compound of titanium and at least one metal selected 
from the groups IVa, Va and VIa of the periodic table excluding titanium, 
and the titanium content as metal atoms contained in the hard dispersed 
phases is in the range of 0.5 to 0.95 an atomic ratio. The wear resistance 
and the deposition resistance of cermet are rendered insufficient if the 
titanium content is less than 0.5. If the titanium content exceeds 0.95, 
on the other hand, the degree of sintering of the cermet deteriorates. 
b. The proportion of nitrogen in nonmetal atoms contained in the hard 
dispersed phases is 0.1 to 0.7 as an atomic ratio. Namely, an effect 
whereby nitrogen atoms suppress the grain growth of the hard dispersed 
phases during sintering, is not attained if the nitrogen proportion is 
less than 0.1. If the nitrogen ratio exceeds 0.7, on the other hand, the 
degree of sintering of cermet deteriorates. 
c. The hard dispersed phases are mixtures of fine-grained hard phases with 
a grain size of 0.2 to 0.6 .mu.m and coarse grained hard phases with a 
grain size of 1.0 to 3.0 .mu.m, wherein the volume ratio of the 
fine-grained hard phases to the coarse-grained hard phases is in the range 
of 0.3 to 3.0. If the ratio is less than 0.3, the toughness is rendered so 
inferior that chipping is caused in the cutting edge part of the drill. If 
the ratio exceeds 3.0, on the other hand, the thermal shock resistance is 
so deteriorated that thermal cracking occurs. 
B. Amount of Binder Metal Phases Contained in the Cermet 
a. The amount of the binder metal phases contained in cermet is in a range 
of 5 percent by weight to 30 percent by weight. If the binder is less than 
5 percent by weight, the toughness is rendered so insufficient that 
chipping is caused in the cutting edge. If the binder exceeds 30 percent 
by weight, on the other hand, the wear resistance is rendered so 
insufficient that significant wear is caused in the flank of the cutting 
edge or of a margin or edge portion of the drill. 
II. Shank Portion 
Since high toughness is required for the shank portion, the difference in 
the thermal expansion coefficient between the same and the cutting edge 
part must be not more than 1.0.times.10.sup.-6 /.degree.C., in order to 
implement a low Young's modulus deformable in response to a bending load 
and to assure an excellent junction with the cutting edge part. 
A. Components of the Hard Dispersed Phases 
a. The hard dispersed phases are composed of a nitride compound of titanium 
or a carbo-nitride compound of titanium and of at least one metal selected 
from the groups IVa, Va and VIa of the periodic table excluding titanium, 
and the titanium content in metal atoms contained in the hard dispersed 
phases is in the range of 0.5 to 0.95 as an atomic ratio. The junction 
strength with the cutting edge part is deteriorated if the titanium ratio 
is less than 0.5. The degree of sintering of the cermet deteriorates if 
the titanium content exceeds 0.95. 
b. The proportion of nitrogen in nonmetal atoms contained in the hard 
dispersed phases is in the range of 0.1 to 0.7 as an atomic ratio. If the 
nitrogen proportion is less than 0.1, the grain growth of the hard 
dispersed phases is caused during sintering of the cermet, and no 
prescribed grain sizes can be obtained. The degree of sintering of the 
cermet deteriorates if the nitrogen content exceeds 0.7. 
c. The grain sizes of the hard dispersed phases are in fine-grained 
structures with a grain size of 0.2 to 0.6 .mu.m. If the grain sizes 
exceed 0.6 .mu.m, the strength of cermet deteriorates and it is not 
possible to maintain a sufficient toughness which is required for the 
shank portion. 
B. Amount of Binder Metal Phases Contained in the Cermet 
The amount of the binder metal phases contained in the cermet is in a range 
of 5 percent by weight to 30 percent by weight. The strength is rendered 
insufficient if the binder metal is less than 5 percent by weight, while 
the cermet causes a plastic deformation if the binder metal exceeds 30 
percent by weight. If the binder metal is out of the aforementioned range 
the difference between the thermal expansion coefficient of the shank and 
the cutting edge part increases undesirably. 
Thus, according to the second embodiment of the invention, a head portion 
and a shank portion which are different in grain size and composition from 
each other, are integrally joined or molded together. 
It has been further found, with regard to a third embodiment of the 
invention that WC-based cemented carbide is preferable used to make the 
drill shank in order to satisfy toughness and strength required for the 
shank portion of a drill. Thus, in a third embodiment, a cermet which is 
excellent in wear resistance and deposition resistance, is employed for 
the head portion of the drill, while WC-based cemented carbide which is 
excellent in toughness, is employed for the shank portion. The head 
portion and the shank portion are integrally joined with each other. The 
characteristics of this drill will now be described. 
I. HEAD SECTION 
A. Components of Hard Dispersed Phases of the Cermet 
a. The hard dispersed phases are composed of a a nitride compound of 
titanium or a carbo-nitride compound of titanium (Ti) and at least metal 
member selected from the groups IVa, Va and VIa of the periodic table 
excluding titanium, and the titanium content in metal atoms contained in 
the hard dispersed phases is in a range of 0.5 to 0.95 as an atomic ratio. 
The wear resistance and deposition resistance of the cermet are rendered 
insufficient if the titanium content is less than 0.5. If the titanium 
content exceeds 0.95, on the other hand, the degree of sintering of the 
cermet deteriorates. 
b. The proportion of nitrogen as nonmetal atoms contained in the hard 
dispersed phases, is in a range of 0.1 to 0.7 as an atomic ratio. If the 
nitrogen is less than 0.1, an effect whereby nitrogen suppresses the grain 
growth of the hard dispersed phases during sintering of the cermet, cannot 
be attained. If the nitrogen exceeds 0.7, on the other hand, the degree of 
the sintering of cermet deteriorates. 
c. The hard dispersed phases are formed of mixtures of fine-grained hard 
phases having a grain size of 0.2 to 0.6 .mu.m and coarse-grained hard 
phases having a grain size of 1 to 3 .mu.m, and the volume ratio of the 
fine-grained hard phases to the coarse-grained hard phases is in a range 
of 0.3 to 3. The toughness of the cermet deteriorates so that chipping is 
caused in the cutting edge of the drill if said volume ratio is less than 
0.3. If the volume ratio exceeds 3.0, on the other hand, thermal cracking 
occurs in the cutting edge of the drill which is a problem. 
B. Amount of Binder Metal Phases Contained in the Cermet 
The amount of the binder metal phases contained in the cermet is in a range 
of 5 percent by weight to 30 percent by weight. If the binder metal is 
less than 5 percent by weight, the toughness of the cermet is rendered so 
insufficient that chipping is caused in the cutting edge of the drill. If 
the binder metal exceeds 30 percent by weight, on the other hand, wear 
resistance is rendered so insufficient that a significant wear is caused 
in the flank of the cutting edge or a margin or edge part. 
II. SHANK SECTION 
A. WC-based cemented carbide containing cobalt used to make the shank 
section of the drill. If high-speed steel or the like is employed for the 
shank, for example, cracks are easily produced in the junction between the 
head section; and the shank section by a thermal expansion difference 
between the shank and the cermet forming the head section, since the 
thermal expansion coefficient of the high speed steel is large. Further, 
the Young's modulus of high-speed steel is about 1/3 that of a WC-based 
alloy whereby wear defects of the head portion are caused by an inferior 
vibration resistance during cutting.

BEST MODES OF CARRYING OUT THE INVENTION 
EXAMPLE 1 
Cermet alloys having various material compositions and grain size 
distributions were used to form drills of 10 mm in diameter by the 
respective materials, and working performances thereof were experimentally 
examined. Table 1 shows compositions etc. of the various alloys subjected 
to the experiment, and alloys Nos. A to C in the Table indicate samples of 
the invention, while D to H indicate comparative samples. Among the 
comparative samples, D and E are used for comparison of proportions of 
nitrogen atoms as nonmetal atoms contained in the hard dispersed phases. 
Further, the comparative sample F is used for comparison of the grain size 
ratios of the hard dispersed phases. In addition, the comparative samples 
G and H are used for comparison of proportions of amounts of binder 
phases. The comparative samples D to H and the samples A to C of the 
invention were studied and compared with each other. 
TABLE 1 
__________________________________________________________________________ 
Hard Dispersed Phase 
Amount of 
Grain Size 
Nonmetal 
Binder Metal 
Abundance 
Composition Ratio 
Atomic 
Phase Ratio of 
Classifi- 
Alloy 
of Metal Atoms 
Ratio (wt. %) 
Hard Phase 
cation No. Ti 
Ta 
W Mo Nb N/C + N 
Ni Co A/B (*1) 
__________________________________________________________________________ 
Inventive 
A 75 
6 12 -- 7 0.38 9 10 2.4 
Sample B 87 
5 8 -- -- 0.41 10 12 1.0 
C 80 
4 5 5 6 0.46 8 10 0.8 
Comparative 
D 80 
5 7 2 6 0 8 12 0.2 
Sample E 73 
6 8 6 7 0.72 10 12 0.1 
F 82 
2 13 -- 3 0.43 9 11 at least 20 
G 73 
8 9 -- 10 0.37 1.5 2.5 
1.1 
H 85 
6 4 -- 5 0.42 15 19 1.4 
__________________________________________________________________________ 
##STR1## 
Table 2 shows conditions of drilling performance evaluation tests for the 
drills. The performance evaluation tests were performed under two types of 
conditions. The test 1 is a wear resistance evaluation test for the 
drills, wherein the drills perform continuous drilling work until the 
drills reach the ends of life due to breakage or wear, as determined by 
evaluating the status of the cutting edges thereof. 
The test 2 is a thermal cracking resistance evaluation test for drills, 
wherein deep hole drilling is performed in the same portion of each 
workpiece a plurality of times for evaluating the cutting edge status 
after the completion of prescribed drillings. 
TABLE 2 
______________________________________ 
Test Condition 
No. Test Name Item Condition 
______________________________________ 
1 Wear Resistance 
Workpiece S50C (H.sub.B = 230) 
Evaluation Test 
Cutting 60 m/min., wet type 
(Continuous Speed (water soluble cutting oil) 
Drilling) Feed Rate 0.23 mm/rev 
Depth 25 mm 
Criterion status of cutting edge after 
working up to end of life 
2 Thermal Cracking 
Workpiece SCM425 (H.sub.B = 260) 
Resistance Cutting 50 m/min., wet type 
Evaluation Test 
Speed (water soluble cutting oil) 
(Step Feed) Feed Rate 0.25 mm/rev 
Depth drawn out every drilling 
by 5 mm and subjected to 
re-drilling. 
repeated 5 times, up to 
25 mm 
Criterion status of cutting edge after 
working 500 holes 
______________________________________ 
In this experiment, a similar cutting test was also performed on a coated 
high-speed steel drill and a coated carbide drill, which are used 
nowadays, for reference. 
Table 3 shows the results of the aforementioned drill performance 
evaluation tests. The following features are are shown by the results of 
the experiments listed shown in Table 3: 
a. In comparing the samples A to C of the invention with the comparative 
samples D and E, it has been found that materials containing large amounts 
of coarse grains in the hard dispersed phases are inferior in shank 
strength and inferior in toughness due to sudden breakage etc., as shown 
by the results of the wear resistance test 1. 
b. In comparing the samples A to C of the invention with the comparative 
sample F, it has been found that the drill is superior in shank strength 
but is significantly inferior in thermal cracking resistance (test 2) when 
the grain sizes of the hard dispersed phases are only fine grains within 
the above grain size range. 
c. In comparing of the samples A to C of the invention with the comparative 
samples G and H, it has been found that the sample (comparative sample G) 
containing a small amount of binder phases is inferior in toughness (test 
1), and the sample (comparative sample H) containing a large amount of 
binder phases is inferior in wear resistance (test 1 and test 2). 
By comparing of these results of the experiments, it has been proven that 
the samples A to C of the invention excellent characteristics over the 
entire aspects of wear resistance, thermal cracking resistance, and shank 
toughness and strength. It has further been found from Table 3 that the 
samples also exhibit excellent characteristics as compared with the coated 
high-speed steel and the coated carbide material. The samples of the 
invention have such features that the present drills exhibit performances 
which are equivalent to those of new drills even if the present drills are 
further used after regrinding. 
TABLE 3 
__________________________________________________________________________ 
Test 1 Test 2 
Classifi- 
Alloy Number of 
Status of 
Status of Cutting 
cation No. Drilling 
Cutting Edge 
Edge 
__________________________________________________________________________ 
Inventive 
A 2450 holes 
normally worn 
good 
Sample B 2390 holes 
normally worn 
good 
C 2660 holes 
normally worn 
good 
Comparative 
D 384 holes 
broken two cracks with 
Sample 500 holes 
E 1248 holes 
broken caused chipping 
with 500 holes 
F 2580 holes 
margin part worn 
got defective 
with 284 holes 
G 104 holes 
got defective 
got defective 
with 32 holes 
H 624 holes 
front flank 
front flank worn 
worn with 245 holes 
Existing 
Coated with 
114 holes 
front flank 
worn with 24 holes 
Sample High-Speed worn 
Steel 
Coated with 
2040 holes 
rake face worn 
rake face worn 
Carbide (Single with 500 holes 
Material) 
Coated with 
1820 holes 
rake face worn 
rake face worn with 
Carbide 500 holes 
(Cutting Edge 
Alone) 
__________________________________________________________________________ 
EXAMPLE 2 
Table 4 shows compositions, grain size distributions etc. of cermet alloys 
used for an experiment. These cermet alloys were used to make drills 
having a diameter of 10 mm, with the respective single materials, and the 
drilling performances thereof were examined. As to the alloy groups shown 
in Table 4, the grain size distributions of the hard dispersed phases were 
noted in the group of alloys AA to FF, for example. Proportions of 
nitrogen as nonmetal atoms were mainly noted in the group of alloys GG to 
II. Further, the amounts of binder phases were mainly noted in the group 
of alloys JJ to MM. 
TABLE 4 
__________________________________________________________________________ 
Hard Dispersed Phase 
Amount of 
Grain Size 
Classifi- Composition Ratio 
Nonmetal 
Bidner Metal 
Abundance Ratio 
cation Alloy 
of Metal Atoms 
Atomic Ratio 
Phase (wt. %) 
of Hard Phase 
(*2) No. Ti 
Ta W Mo Nb N/C + N 
Ni Co A/B (*1) 
__________________________________________________________________________ 
Invention 
AA 85 
7 8 -- -- 0.42 10 10 at least 20 
Sample 1 
Comparative 
BB 85 
7 8 -- -- 0.42 10 10 4.0 
Sample 
Inventive 
CC 85 
7 8 -- -- 0.42 10 10 2.5 
Sample 2 
Inventive 
DD 85 
7 8 -- -- 0.42 10 10 1.0 
Sample 2 
Comparative 
EE 85 
7 8 -- -- 0.42 10 10 0.2 
Sample 
Comparative 
FF 85 
7 8 -- -- 0.42 10 10 at least 20 
Sample 
Comparative 
GG 80 
10 7 -- 3 0.08 8 7 1.5 
Sample 
Inventive 
HH 80 
6 5 2 7 0.36 9 5 1.5 
Sample 2 
Comparative 
II 83 
4 5 2 6 0.75 10 6 1.5 
Sample 
Comparative 
JJ 73 
8 9 -- 10 0.38 3 1.5 not more than 0.05 
Sample 
Inventive 
KK 81 
7 4 -- 8 0.41 12 10 not more than 0.05 
Sample 1 
Inventive 
LL 85 
6 4 -- 5 0.42 12 8 0.7 
Sample 2 
Comparative 
MM 82 
4 1 3 10 0.32 20 20 not more than 0.05 
Sample 
__________________________________________________________________________ 
##STR2## 
(*2) Invention Sample 1: for Shank 
Invention Sample 2: for Cutting Edge 
Performance evaluation tests were made under the conditions shown in Table 
5, namely, a wear resistance evaluation test and a thermal cracking 
resistance evaluation test. Table 6 shows the results of the respective 
tests. 
TABLE 5 
______________________________________ 
Test Condition 
No. Test Name Item Condition 
______________________________________ 
1 Wear Resistance 
Workpiece S50C (H.sub.B = 230) 
Evaluation Test 
Cutting 60 m/min., wet type 
(Continuous Speed (water soluble cutting oil) 
Drilling) Feed Rate 0.23 mm/rev 
Depth 25 mm 
Criterion status of cutting edge after 
working up to end of life 
2 Thermal Cracking 
Workpiece SCM425 (H.sub.B = 260) 
Resistance Cutting 50 m/min., wet type 
Evaluation Test 
Speed (water soluble cutting oil) 
(Step Feed) Feed Rate 0.25 mm/rev 
Depth drawn out every drilling 
by 5 mm and subjected to 
re-drilling. 
repeated 5 times, up to 
25 mm 
Criterion status of cutting edge after 
working 500 holes 
______________________________________ 
TABLE 6 
__________________________________________________________________________ 
Test 1 Test 2 
Classifi- 
Alloy 
Number of 
Status of 
Status of 
cation No. Drilling 
Cutting Edge 
Cutting Edge 
__________________________________________________________________________ 
Invention 
AA 2550 holes 
margin worn 
chipped with 224 holes 
Sample 1 caused chipping with 
Comparative 
BB 2610 holes 
margin worn 
500 holes 
Sample 
Invention 
CC 2430 holes 
shank broken 
good 
Sample 2 
DD 2580 holes 
shank broken 
good 
Comparative 
EE 2110 holes 
front flank worn 
broken with 128 holes 
Sample FF 505 holes 
broken good 
Comparative 
GG 1420 holes 
broken caused chipping with 
Sample 280 holes 
Invention 
HH 2500 holes 
shank broken 
good 
Sample 2 
Comparative 
II 2780 holes 
margin worn 
margin chipped with 
Sample 500 holes 
Comparative 
JJ 160 holes 
chipped chipped with 15 holes 
Sample 
Invention 
KK 2410 holes 
margin worn 
chipped with 328 holes 
Sample 1 
Invention 
LL 2640 holes 
shank broken 
good 
Sample 2 front flank worn with 
Comparative 
MM 480 holes 
front flank worn 
240 holes 
Sample 
__________________________________________________________________________ 
In the results of the group of the alloys AA to FF, the alloys AA to DD 
having relatively fine grain sizes of hard dispersed phases, had an 
excellent wear resistance. The alloys EE and FF caused sudden breakage. 
The alloys AA and BB having fine grain sizes, exhibited an inferior 
thermal cracking resistance. The alloy AA had the most excellent shank 
strength. The samples showed a tendency of becoming worse as the grain 
sizes of the hard dispersed phases were roughened (group of alloys CC to 
FF). 
Thus, it has been shown that the alloys CC and DD are excellent in wear 
resistance and thermal cracking resistance and the alloy AA is excellent 
in shank strength in the group of the alloys AA to FF. 
It has been shown that the life of the alloy GG is short and the alloy II 
is inferior in shank strength in the alloys GG to II. 
In the group of the alloys JJ to MM, the alloy KK exhibited a superior 
shank strength, and the alloy LL exhibited a superior thermal cracking 
resistance. From the results, the alloy KK has properties suitable for a 
shank portion, and the alloy LL has properties suitable for a cutting edge 
part. 
From the results shown in Table 6, the alloys CC, DD, HH and LL were 
selected as alloys having properties suitable for a head portion of a 
drill, and the alloys AA and KK were selected as alloys having properties 
suitable for a shank portion of the drill. Several types of drills were 
made by integrally joining and molding these alloys respectively, and the 
resulting drills were subjected to performance evaluation tests. Table 7 
shows combinations of the alloys employed for the cutting edge parts and 
for the shank portions of the drills and the results of the evaluation 
tests thereof. The performance evaluation tests were made in accordance 
with the conditions shown in Table 5. Methods of joining alloys with each 
other include thermal diffusion, or a method of joining and molding the 
respective samples in a powder compression molding process and thereafter 
integrating the same by sintering. The methods are used for forming and 
connecting the cutting edge parts and the shank portions of the drills. 
For the purpose of reference, Table 7 also shows test results of a 
currently used coated high-speed drill and coated carbide drills. 
TABLE 7 
__________________________________________________________________________ 
Composite 
Combination 
Test 1 Test 2 
Alloy Cutting Number of 
Status of 
Status of 
No. Edge 
Shank 
Drilling 
Cutting Edge 
Cutting Edge 
__________________________________________________________________________ 
NN CC AA 2790 holes 
margin worn 
good 
OO DD AA 2680 holes 
front flank worn 
good 
PP DD KK 2730 holes 
front flank worn 
good 
QQ HH KK 2840 holes 
front flank worn 
good 
Coated with High-Speed 
145 holes 
front flank worn 
worn with 20 holes 
Steel 
Coated with Carbide 
1980 holes 
rake face worn 
rake face worn 
(Single Material) chipped with 500 holes 
Coated with Carbide 
1770 holes 
rake face worn 
rake face worn 
(Cutting Edge Alone) with 500 holes 
__________________________________________________________________________ 
Comparing the results of the performance evaluation tests shown in Table 7 
with Table 6, it is clear that every one of the present composite alloys 
NN to QQ has a good wear resistance, a good thermal cracking resistance 
and a high toughness. Further, the composite alloys NN to QQ caused 
absolutely no breakage which was suddenly caused in the alloys EE and FF, 
for example, in the performance evaluation tests shown in Table 6. In 
addition, it has been found that the present composite alloys have a high 
quality since no change was recognized in various properties thereof even 
if the head portions were reground. 
EXAMPLE 3 
A sintered hard alloy drill is formed by using a cermet alloy for a head 
portion, using WC cemented carbide for a shank portion, joining the same 
to each other by press forming of fine particles, and sintering the same. 
Table 8 shows compositions and grain size distributions of the cermet 
alloy portions of sintered hard alloy drills subjected to performance 
tests and drills used for comparison. Referring to Table 8, alloys DDD and 
EEE of comparative samples were used mainly noting proportions of nonmetal 
atoms contained in the hard dispersed phases. Further, an alloy FFF of the 
comparative sample was used noting the grain size distribution of the hard 
dispersed phases. In addition, alloys GGG and HHH of the comparative 
samples were used noting proportions of the binder metal phases contained 
in the cermet materials. 
TABLE 8 
__________________________________________________________________________ 
Hard Dispersed Phase 
Amount of 
Grain Size 
Nonmetal 
Binder 
Abundance 
Composition Ratio 
Atomic 
Phase Ratio of 
Classifi- 
Alloy 
of Metal Atoms 
Ratio (Wt. %) 
Hard Phase 
cation No. Ti 
Ta W Mo Nb N/C + N 
Ni Co. 
A/B (*1) 
__________________________________________________________________________ 
Inventive 
AAA 83 
7 10 -- -- 
0.42 10 11 2.3 
Sample BBB 72 
4 10 4 10 
0.37 9 10 1.0 
CCC 88 
5 5 -- 2 0.50 7 14 0.7 
Comparative 
DDD 86 
5 4 -- 5 0 10 11 0.2 
Sample EEE 80 
6 5 2 7 0.75 8 12 0.1 
FFF 73 
8 9 -- 10 
0.40 9 10 at least 20 
GGG 82 
10 3 1 4 0.46 2 2 1.2 
HHH 80 
10 7 1 2 0.32 13 18 1.5 
__________________________________________________________________________ 
##STR3## 
Performance evaluation tests of the drills were made by producing drills 
having a diameter of 10 mm, of the materials of the alloys AAA to HHH 
shown in Table 8, under conditions shown in Table 9. The performance 
evaluation tests are mainly performed as a wear resistance evaluation test 
and as a thermal cracking resistance test. 
TABLE 9 
______________________________________ 
Test Condition 
No. Test Name Item Condition 
______________________________________ 
1 Wear Resistance 
Workpiece S50C (H.sub.B = 230) 
Evaluation Test 
Cutting 55 m/min., wet type 
(Continuous Speed (water soluble cutting oil) 
Drilling) Feed Rate 0.21 mm/rev 
Depth 25 mm 
Criterion status of cutting edge after 
working up to end of life 
2 Thermal Cracking 
Workpiece SCM435 (H.sub.B = 280) 
Resistance Cutting 50 m/min., wet type 
Evaluation Test 
Speed (water soluble cutting oil) 
(Step Feed) Feed Rate 0.23 mm/rev 
Depth drawn out every drilling 
by 5 mm and subjected to 
re-drilling. 
repeated 5 times, up to- 25 mm 
Criterion status of cutting edge after 
working 500 holes 
______________________________________ 
Table 10 shows the results of the aforementioned drill performance 
evaluation tests. Referring to Table 10, the alloys DDD and EEE were 
inferior particularly in the toughness of the cutting edge, and suddenly 
caused breakage during the test 1 comparing of the alloys AAA to CCC with 
the alloys DDD and EEE. 
In comparing of the alloys AAA to CCC with the alloy FFF, it has been shown 
that the alloy FFF was inferior in thermal cracking resistance. 
In comparing of the alloys AAA to CCC with the alloys GGG and HHH, it has 
been shown that the alloy GGG was inferior in thermal cracking resistance 
and its life was extremely short. It has also been shown that the alloy 
HHH was inferior in wear resistance. 
For the purpose of comparison, the performance tests were also made on 
currently used coated high-speed steel or coated carbide drills. Comparing 
these drills with the drills of the alloys AAA to CCC, it is clear that 
the performances of the drills of the present invention samples are 
superior in any test. 
The performance evaluation tests were also made on the alloys AAA to CCC 
representing samples of the invention, and on drill with a tip and shank 
made of a single material of the alloy AAA and a drill with a tip and 
shank made of a single material of WC cemented carbide, for example. As a 
result, a characteristic improvement is noted in the strength of the alloy 
AAA according to the present invention as in the sample of the invention 
compared to the alloy AAA as used in the single material sample. Comparing 
the alloy AAA in the sample of the invention with the WC cemented carbide, 
makes, it is clear that the alloy AAA according to the present invention 
is superior in both wear resistance and strength. 
TABLE 10 
__________________________________________________________________________ 
Test 1 Test 2 
Classifi- 
Alloy Number of 
Status of 
Status of 
cation No. Drilling 
Cutting Edge 
Cutting Edge 
__________________________________________________________________________ 
Invention 
AAA 2630 holes 
normally worn 
good 
Sample BBB 2440 holes 
normally worn 
good 
CCC 2540 holes 
normally worn 
good 
Comparative 
DDD 390 holes 
broken two cracks with 
Sample 500 holes 
EEE 1308 holes 
broken caused chipping 
with 500 holes 
FFF 2480 holes 
margin worn 
chipped with 
343 holes 
GGG 212 holes 
chipped chipped with 
82 holes 
HHH 845 holes 
front flank worn 
worn with 
245 holes 
Reference 
Coated with 
84 holes 
front flank worn 
worn with 
High-Speed 18 holes 
Steel 
Coated with 
2120 holes 
rake face worn 
rake face worn 
Carbide with 500 holes 
(Single 
Material) 
Coated with 
1940 holes 
rake face worn 
rake face worn 
Carbide with 500 holes 
(Cutting Edge 
Alone) 
Alloy AAA 
1420 holes 
broken good 
(Single 
Material) 
WC Cemented 
1430 holes 
entirely signifi- 
cause chipping 
Carbide cantly worn 
with 342 holes 
__________________________________________________________________________ 
As hereinabove described, the cermet alloy containing nitrogen according to 
the present invention is advantageously applicable to making drills, and 
end mill, a cutting tool for milling or the like, for which excellent 
properties are required in wear resistance, toughness and high-speed 
cutting.