# Patent

## Title
Highly corrosion-resistant, colored thin film-coated steel sheet having

## Abstract

A blade member for cutting-tools includes a cermet substrate which contains, apart from unavoidable impurities, a binder phase and a hard dispersed phase. The binder phase contains 5% to 30% by weight of cobalt and/or nickel. The hard dispersed phase contains a balance composite carbonitride of titanium and one or more of the elements tungsten, molybdenum, tantalum, niobium, hafnium and zirconium. The composite carbo-nitride satisfies the relationship 0.2.ltoreq.b/(a+b).ltoreq.0.7, where a and b denote atomic ratios of carbon and nitrogen, respectively. The substrate includes a hard surface layer in which the maximum hardness is present at a depth between 5 .mu.m and 50 .mu.m from a substrate surface thereof. The substrate surface has a hardness of 20% to 90% of the maximum hardness.

## Background
1. Field of the Invention

The present invention relates to a cermet blade member which is particularly suitable for cutting-tools used in interrupted cutting operations under particularly severe conditions.

2. Prior Art

As disclosed in Japanese Unexamined Patent Application Publication No. 54-139815, there was hitherto developed a cermet blade member which consists, apart from unavoidable impurities, of a binder phase of 5% to 30% by weight of at least one of cobalt (Co) and nickel (Ni); and a dispersed phase of a balance composite carbo-nitride of titanium (Ti) with at least one of the elements of tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb), hafnium (Hf) and zirconium (Zr); and which includes a hard surface layer wherein hardness is greatest at the surface.

The aforesaid cermet blade member is manufactured by a sintering method which includes heating a green compact of a prescribed blend composition to a prescribed temperature of no greater than the liquid phase-emerging temperature in a carburizing atmosphere of CO and CH.sub.4, or the like, and subsequently carrying out the temperature elevating step to a sintering temperature and a subsequent holding step in a vacuum.

The aforesaid blade member exhibits a superior wear resistance when used for cutting-tools designed for high speed cutting of steel or the like. However, the blade member is susceptible to fracture or chipping when used for interrupted cutting or heavy duty cutting operations where a greater toughness and shock resistance are required, so that the blade member cannot be employed under such circumstances.

It is therefore an object of the present invention to provide a cermet blade member which not only exhibits superior wear resistance but also is less susceptible to fracture.

Another object of the invention is to provide a process for producing the above blade member.

According to a first aspect of the invention, there is provided a cermet blade member for cutting-tools, comprising a cermet substrate consisting, apart from unavoidable impurities, of a binder phase of 5% to 30% by weight of at least one element selected from the group consisting of cobalt and nickel; and a hard dispersed phase of a balance composite carbo-nitride of titanium and at least one element selected from the group consisting of tungsten, molybdenum, tantalum, niobium, hafnium and zirconium, the composite carbo-nitride satisfying the relationship of 0.2.ltoreq.b/(a+b)<0.7, where a and b denote atomic ratios of carbon and nitrogen, respectively; the substrate including a hard surface layer in which the maximum hardness is present at a depth between 5 .mu.m and 50 .mu.m from the substrate surface thereof, the substrate surface having hardness of 20% to 90% of the greatest hardness.

According to a second aspect of the invention, there is provided a process for producing a cermet blade member for cutting-tools, comprising the steps of mixing powders for forming the binder phase and the hard dispersed phase to provide a powder mixture of a prescribed composition, compacting the powder mixture into a green compact, and sintering the green compact to provide the substrate of cermet, the sintering step including initial temperature elevation in a non-oxidizing atmosphere and subsequent temperature elevation to a temperature ranging from 1,100.degree. C. to 1,500.degree. C. in a nitrogen atmosphere, and a subsequent sintering operation in a denitrifying atmosphere such as vacuum .

FIGS. 1 to 4 are diagrammatical representations showing several patterns of the sintering process in accordance with the process of the invention.

The inventors have made an extensive study in order to improve the prior art cermet blade member and have produced a blade member in accordance with the present invention which comprises a cermet substrate consisting, apart from unavoidable impurities, of a binder phase of 5% to 30% by weight of at least one element selected from the group consisting of cobalt and nickel, and a hard dispersed phase of a balance composite carbo-nitride of titanium and at least one element selected from the group consisting of tungsten, molybdenum, tantalum, niobium, hafnium and zirconium. The dispersed phase may further contain at least one compound selected from the group consisting of tungsten carbide and titanium nitride. The composite carbo-nitride is formed so as to satisfy the relationship 0.2.ltoreq.b/(a+b).ltoreq.0.7, where a and b denote atomic ratios of carbon and nitrogen, respectively. In addition, the substrate includes a hard surface layer having the maximum hardness at a depth of between 5 .mu.m and 50 .mu.m from the substrate surface thereof, and the surface has a hardness of 20% to 90% of the abovementioned maximum hardness value.

The blade member of the aforesaid construction has superior fracture resistance characteristics, and therefore exhibits superior cutting performance when used in interrupted cutting operations of steel or the like under particularly severe conditions. In addition, the blade member also exhibits a high wear resistance, and therefore the resulting cutting-tool achieves a good performance for high speed cutting for an extended period of time.

In the foregoing, cobalt and nickel are included to improve toughness of the substrate of the blade member. Accordingly, if the cobalt content or nickel content is below 5% by weight, the resulting blade member loses the required degree of toughness. On the other hand, if the content exceeds 30% by weight, the hardness and hence the wear resistance is lowered.

Furthermore, the substrate of the above blade member is formed so that the hardest region in the hard surface layer is present at a depth of between 5 .mu.m, and 50 .mu.m from the substrate surface. If its position is shallower than 5 .mu.m, the blade member cannot have desired fracture resistance characteristics. On the other hand, if the position is deeper than 50 .mu.m, cutting edges of the blade member will be subjected to wear before the occurrence of a sufficient wear resistance effect by virtue of the hard surface layer, thereby reducing the cutting performance unduly.

In addition, the atomic ratios of carbon and nitrogen in the composite carbo-nitride have an influence on the degree of sintering for cermet and a hardness distribution in the substrate. If the ratio defined by b/(a+b) is below 0.2, the nitrogen content is too low relative to the carbon content. As a result, in conjunction with sintering conditions, the hardest region in the substrate shifts toward the substrate surface, and therefore the hardest region cannot be maintained at the previously-described desired depth ranging between 5 .mu.m and 50 .mu.m. On the other hand, if the above ratio exceeds 0.7, the nitrogen content is too high relative to the carbon content to maintain a sufficient degree of sintering, thereby failing to ensure the desired high degree of toughness.

Furthermore, if the hardness at the substrate surface is greater than 90% of the maximum hardness value, the difference between the hardness at the substrate surface and the maximum hardness is too small, and the blade member becomes susceptible to fracture. On the other hand, if the hardness at the substrate surface is less than 20% of the maximum hardness value, the substrate surface will be subjected to rapid wear, so that the life of the blade member is shortened.

Furthermore, in order to further improve the cutting performance, a hard coating having an average thickness of 0.5 .mu.m to 20 .mu.m may be formed on the substrate. The hard coating may be composed of either diamond or cubic boron nitride (CBN). The hard coating may also be composed of at least one compound selected from the group consisting of: a carbide, a nitride, an oxide and a boride of at least one element, selected from the class consisting of titanium, zirconium, hafnium, aluminum and silicon; and solid solution compounds of two or more of the carbide, nitride, oxide and boride of the at least one element. The hard coating may include one or more layers.

For producing the aforesaid blade member, a powder metallurgical process is utilized. Specifically, powders for forming the binder phase and the hard dispersed phase are first prepared and blended at a predetermined composition to provide a powder mixture. Thereafter, the mixture is compacted into a green compact and sintered. In the sintering operation, initial temperature elevation is effected in a non-oxidizing atmosphere such as a vacuum or an inert gas atmosphere. In the subsequent temperature elevation from 1,100.degree. C., above which nitrides or carbo-nitrides are susceptible to decomposition, to a sintering temperature Ts ranging from 1,400.degree. C. to 1,500.degree. C., a gaseous nitrogen atmosphere is used. Then, the subsequent sintering step including the cooling step is effected in a denitrifying atmosphere such as a vacuum. According to the above sintering process, there are four possible patterns (A), (B), (C) and (D) as depicted in FIGS. 1 to 4, respectively. Among the four patterns, (B) and (C) are preferable in order to obtain a better blade member.

The hard coating of the aforesaid construction may be formed on the substrate thus produced by means of a known physical or chemical vapor deposition method.

In the above blade member, the position of the hardest region in the hard surface layer can be regulated by changing the ratio b/(a+b) in the composite carbo-nitride during the blending step or by modifying the sintering conditions. For instance, if the blending is effected so that the ratio b/(a+b) in the composite carbo-nitride in the resulting substrate becomes greater (i.e., the nitrogen content therein becomes greater), the hardest region will shift to the inner or deeper position, and accordingly the hardness at the substrate surface will be lowered. Moreover, if the sintering step in the denitrifying atmosphere is prolonged to enhance the degree of denitrification, the position of the hardest region will shift inwardly of the substrate. On the other hand, if the step in the denitrifying atmosphere is shortened, the hardest region will shift toward the substrate surface and hence the hardness at the substrate surface increases.

The present invention will now be described in detail with reference to the following example.

Powders of TiC, TiN, WC, Mo.sub.2 C, TaC, NbC, HfC, ZrC, Co and Ni were prepared, each of which having a prescribed average particle size ranging from 1 .mu.m to 1.5 .mu.m. These powders were blended in various blend compositions depicted in Tables 1 to 4 and were subjected to wet mixing in a ball mill for 72 hours. After being dried, each mixture was pressed into a green compact of a shape in conformity with SNMG120408 of the ISO Standards. Subsequently, the green compact was sintered under the following conditions:

Specifically, the green compact was first heated from the ordinary temperature to 1,100.degree. C. in a vacuum, and further heated from 1,100.degree. C. to 1,450.degree. C. in a nitrogen atmosphere of 10 torr. Then, the atmosphere was removed to produce a vacuum of 10.sup.-2 torr, in which the compact was held for 1 hour and in which the subsequent cooling step was carried out.

With the above sintering procedures, cutting inserts 1 to 23 of the invention were manufactured.

Furthermore, for comparison purposes, the green compacts having the same compositions as the cutting inserts of the invention were prepared and sintered under the following conditions:

Specifically, each compact was heated from the ordinary temperature to 1,100.degree. C. in a gaseous carbon monoxide (CO) atmosphere of 50 torr, and the subsequent operation, which included the temperature elevation step from 1,100.degree. C. to 1,450.degree. C. (starting temperature of the holding step), the holding step of the compact for 1 hour and the cooling step from the above temperature to the ordinary temperature, was effected in a vacuum of 10.sup.-2 torr. With these procedures, comparative cutting inserts 1 to 23 were produced as depicted in Tables 5 to 8.

Then, the hardness, which was based on micro Vickers (load: 100 g) measurements on an inclined surface having an angle of 11.degree., was measured for each cutting insert and the results are set forth in Tables 1 to 8. In the experiment, carbides and nitrides of a single element were used, but carbo-nitrides of a single element or a solid solution of composite carbides, nitrides or carbo-nitrides of plural elements could be used as well.

Subsequently, in order to evaluate fracture resistance characteristics, the cutting inserts thus obtained were subjected to dry-type interrupted cutting tests of steel under the following conditions:

In this test, the number of inserts subjected to fracture per ten was determined.

Similarly, in order to evaluate the wear resistance, all of the cutting inserts were subjected to a dry-type continuous high-speed cutting test, and flank wear was observed. The conditions of this test were as follows:

The results of the above two tests are set forth in Tables 1 to 8.

As clearly seen from the results, the inserts of the present invention are comparable to the comparative cutting inserts in the degree of wear resistance. However, the inserts of the present invention exhibit greater fracture resistance characteristics than the comparative inserts. __________________________________________________________________________ Substrate Maximum Surface  Hardness               Frank Composition of hard- hardness Hard-                  Wear (% by weight)Blend Composition (% by weight)Substrate ##STR1## (Hv)ness (%)percent (Hv)ness (.mu.m)Depth HardnessInternal ##STR2##  (mm)Width __________________________________________________________________________ Cutting Inserts of the Invention 1 Ni:6 TaC:8 Ni:6      0.24 1780 88.1 2020 5   1720 3/10      0.11 Mo.sub.2 C:10 TiN:20 (Ti, Ta, Mo) TiC:other (CN):other 2 Co:8 Ni:4 NbC:2 Co:8 Ni:4 TiN:6 0.44  590 26.5 2230 40   1680 3/10      0.12 TaC:10 WC:10 (Ti, Ta, Nb, W, Mo.sub.2 C:10 TiN:30 Mo) (CN):other TiC:other 3 Co:4 Ni:8 NbC:3 Co:4 Ni:8 TiN:5 0.45 1580 75.6 2090 15   1670 1/10      0.12 TaC:10 WC:10 (Ti, Nb, Ta, W, Mo.sub.2 C:10 TiN:30 Mo) (CN):other TiC:other 4 Co:10 Ni:5 NbC:5 Co:10 Ni:5 TiN:10 0.50  730 37.2 1960 45   1650 0/10      0.24 TaC:10 WC:10 (Ti, Ta, Nb, W) TiN:35 TiC:other (CN):other 5 Co:12 Ni:4 TaC:15 Co:12 Ni:4 TiN:8 0.55 1630 85.3 1910 15   1650 0/10      0.18 WC:15 TiN:35 (Ti, Ta, W) TiC:other (CN):other 6 Co:12 Ni:4 TaC:10 Co:12 Ni:4 WC:8 0.44 1680 87.5 1960 20   1670 0/10      0.22 WC:30 TiN:25 (Ti, Ta, W) TiC:other (CN):other __________________________________________________________________________ __________________________________________________________________________ Substrate Maximum Surface  Hardness               Frank Composition of hard- hardness Hard-                  Wear (% by weight)Blend Composition (% by weight)Substrate ##STR3## (Hv)ness (%)percent (Hv)ness (.mu.m)Depth HardnessInternal ##STR4##  (mm)Width __________________________________________________________________________ Cutting Inserts of the Invention 7 Co:12 Ni:6 NbC:2 Co:12 Ni:6 0.32 1600 87.9 1920 10   1590 0/10      0.16 TaC:15 WC:15 (Ti, Ta, Nb, W) TiN:20 TiC:other (CN):other 8 Co:10 Ni:8 TaC:5 Co:10 Ni:8 TiN:5 0.45 1480 80.4 1940 20   1540 0/10      0.18 NbC:5 WC:15 (Ti, Ta, Nb, W) TiN:30 TiC:other (CN):other 9 Co:12 Ni:6 NbC:5 Co:12 Ni:6 WC:10 0.59  860 44.6 1930 40   1520 0/10      0.25 TaC:5 WC:25 TiN:3 (Ti, Ta, Nb, TiN:35 TiC:other W) (CN):other 10 Co:10 Ni:6 NbC:2 Co:10 Ni:6 WC:13 0.47 1280 63.7 2010 30   1610 0/10      0.25 TaC:10 WC:35 (Ti, Ta, Nb, W) TiN:25 TiC:other (CN):other 11 Co:12 Ni:6 NbC:3 Co:12 Ni:6 TiN:8 0.52 1180 57.6 2050 35   1540 0/10      0.19 TaC:8 WC:5 (Ti, Ta, Nb, W, Mo.sub.2 C:8 TiN:35 Mo) (CN) TIC:other 12 Co:15 Ni:10 NbC:5 Co:15 Ni:10 TiN:12 0.68 1380 76.7 1960 45   1450 0/10      0.27 TaC:10 TiN:45 (Ti, Ta, Nb) TiC:other (CN):other __________________________________________________________________________ __________________________________________________________________________ Substrate Maximum Surface  Hardness               Frank Composition of hard- hardness Hard-                  Wear (% by weight)Blend Composition (% by weight)Substrate ##STR5## (Hv)ness (%)percent (Hv)ness (.mu.m)Depth HardnessInternal ##STR6##  (mm)Width __________________________________________________________________________ Cutting Inserts of the Invention 13 Co:14 Ni:14 Co:14 Ni:14 0.31 1500 82.9 1960 25   1400 0/10      0.28 ZrC:0.5 NbC:5 (Ti, Zr, Nb, Mo.sub.2 C:10 TiN:20 Mo) (CN):other TiC:other 14 Co:14 Ni:14 Co:14 Ni:14 0.46  680 33.8 2010 40   1380 0/10      0.30 ZrC:0.1 NbC:3 TiN:10 (Ti, Zr, Nb, TaC:10 WC:10 Ta, W) (CN):other TiN:40 TiC:other 15 Co:4 Ni:4 TaC:8 Co:4 Ni:4 0.25 1600 80.8 1980 10   1680 2/10      0.15 WC:6 Mo.sub.2 C:8 (Ti, Ta, W, Mo) TiN:20 TiC:other (CN):other 16 Co:6 Ni:6 TaC:10 Co:6 Ni:6 0.55  760 35.8 1650 45   1650 1/10      0.17 WC:8 Mo.sub.2 C:5 TiN:10 (Ti, Ta, W, TiN:40 TiC:other Mo) (CN):other 17 Co:7 Ni:7 NbC:2 Co:7 Ni:7 TiN:5 0.43 1630 75.8 2150 5   1640 0/10      0.16 TaC:4 WC:10 (Ti, Ta, Nb, W, Mo.sub.2 C:10 TiN:30 Mo) (CN):other TiC:other 18 Co:8 Ni:10 Co:8 Ni:10 TiN:5 0.45  870 41.8 2080 40   1570 0/10      0.20 NbC:5 TaC:5 (Ti, Ta, Nb, W, WC:8 Mo.sub.2 C:8 Mo) (CN):other TiN:30 TiC:other __________________________________________________________________________ __________________________________________________________________________ Substrate Maximum Surface  Hardness               Frank Composition of hard- hardness Hard-                  Wear (% by weight)Blend Composition (% by weight)Substrate ##STR7## (Hv)ness (%)percent (Hv)ness (.mu.m)Depth HardnessInternal ##STR8##  (mm)Width __________________________________________________________________________ Cutting Inserts of the Invention 19 Co:16 NbC:10 Co:16 TiN:10 0.57 1670 87.0 1920 10   1650 0/10      0.19 WC:15 TiN:40 (Ti, Nb, W) TiC:other (CN):other 20 Co:10 Ni:12 Co:10 Ni:12 TiN:8 0.56  610 28.6 2130 45   1420 0/10      0.25 TaC:5 Mo.sub.2 C:10 (Ti, Ta, W, Mo) WC:8 TiN:35 (CN):other TiC:other 21 Co:12 Ni:6 Co:12 Ni:6 0.34 1520 80.4 1890 5   1620 0/10      0.20 TaC:10 Mo.sub.2 C:10 (Ti, Ta, Mo, W) WC:15 TiN:20 (CN):other TiC:other 22 Co:10 Ni:10 Co:10 Ni:10 TiN:3 0.35 1460 77.7 1880 10   1450 0/10      0.23 Mo.sub.2 C:15 TiN:25 (Ti, Mo) TiC:other (CN):other 23 Co:20 Ni:5 Co:20 Ni:5 TiN:3 0.40 1210 65.4 1910 14   1430 0/10      0.26 TaC:5 Mo.sub.2 C:5 (Ti, Ta, Mo, W, WC:10 TiN:25 Hf) (CN):other HfC:0.5 TiC:other __________________________________________________________________________ __________________________________________________________________________ Substrate Maximum Surface  Hardness               Frank Composition of hard- hardness Hard-                  Wear (% by weight)Blend Composition (% by weight)Substrate ##STR9## (Hv)ness (%)percent (Hv)ness (.mu.m)Depth HardnessInternal ##STR10## (mm)Width __________________________________________________________________________ Comparative Cutting Inserts 1 Ni:6 TaC:8 Ni:6      0.18 1920 --   1920 --   1730 10/10     0.25 Mo.sub.2 C:10 TiN:20 (Ti, Ta, Mo) TiC:other (CN):other 2 Co:8 Ni:4 NbC:2 Co:8 Ni:4 0.38 1870 --   1870 --   1670 9/10      0.28 TaC:10 WC:10 (Ti, Ta, Nb, W, Mo.sub.2 C:10 TiN:30 Mo) (CN):other TiC:other 3 Co:4 Ni:8 NbC:3 Co:4 Ni:8 0.35 1950 --   1950 --   1670 9/10      0.27 TaC:10 WC:10 (Ti, Nb, Ta, W, Mo.sub.2 C:10 TiN:30 Mo) (CN):other TiC:other 4 Co:10 Ni:5 Co:10 Ni:5 TiN:3 0.36 1860 --   1860 --   1650 9/10      0.30 NbC:5 NbC:10 (Ti, Ta, Nb, W) WC:10 TiN:35 (CN):other TiC:other 5 Co:12 Ni:4 TaC:15 Co:12 Ni:4 TiN:3 0.48 1880 --   1880 --   1630 8/10      0.28 WC:15 TiN:35 (Ti, Ta, W) TiC:other (CN):other 6 Co:12 Ni:4 TaC:10 Co:12 Ni:4 0.38 1890 --   1890 --   1650 7/10      0.30 WC:30 TiN:25 (Ti, Ta, W) TiC:other (CN):other __________________________________________________________________________ __________________________________________________________________________ Substrate Maximum Surface  Hardness               Frank Composition of hard- hardness Hard-                  Wear (% by weight)Blend Composition (% by weight)Substrate ##STR11## (Hv)ness (%)percent (Hv)ness (.mu.m)Depth HardnessInternal ##STR12## (mm)Width __________________________________________________________________________ Comparative Cutting Inserts 7 Co:12 Ni:6 NbC:2 Co:12 Ni:6 0.25 1830 --   1830 --   1620 7/10      0.30 TaC:15 Wc:15 (Ti, Ta, Nb, W) TiN:20 TiC:other (CN):other 8 Co:10 Ni:8 TaC:5 Co:10 Ni:8 0.41 1810 --   1810 --   1530 7/10      0.31 NbC:5 WC:15 (Ti, Ta, Nb, W) TiN:30 TiC:other (CN):other 9 Co:12 Ni:6 NbC:5 Co:12 Ni:6 0.48 1800 --   1800 --   1510 7/10      0.32 TaC:5 WC:25 TiN:3 (Ti, Ta, Nb, TiN:35 TiC:other W) (CN):other 10 Co:10 Ni:6 NbC:2 Co:10 Ni:6 WC:4 0.41 1910 --   1910 --   1590 8/10      0.28 TaC:10 WC:35 (Ti, Ta, Nb, W) TiN:25 TiC:other (CN):other 11 Co:12 Ni:6 NbC:3 Co:12 Ni:6 0.39 1850 --   1850 --   1560 7/10      0.33 TaC:8 WC:5 (Ti, Ta, Nb, W, Mo.sub.2 C:8 TiN:35 Mo) (CN) TiC:other 12 Co:15 Ni:10 NbC:5 Co:15 Ni:10 TiN:5 0.58 1800 --   1800 --   1480 7/10      0.47 TaC:10 TiN:45 (Ti, Ta, Nb) TiC:other (CN):other __________________________________________________________________________ __________________________________________________________________________ Substrate Maximum Surface  Hardness               Frank Composition of hard- hardness Hard-                  Wear (% by weight)Blend Composition (% by weight)Substrate ##STR13## (Hv)ness (%)percent (Hv)ness (.mu.m)Depth HardnessInternal ##STR14## (mm)Width __________________________________________________________________________ Comparative Cutting Inserts 13 Co:14 Ni:14 Co:14 Ni:14 0.27 1790 --   1790 --   1420 6/10      0.55 ZrC:0.5 NbC:5 (Ti, Zr, Nb, Mo.sub.2 C:10 TiN:20 Mo) (CN):other TiC:other 14 Co:14 Ni:14 Co:14 Ni:14 0.33 1710 --   1710 --   1390 6/10      0.58 ZrC:0.1 NbC:3 TiN:3 (Ti, Zr, Nb, TaC:10 WC:10 Ta, W) (CN):other TiN:10 TiC:other 15 Co:4 Ni:4 TaC:8 Co:4 Ni:4 0.19 1890 --   1890 --   1710 10/10    0.25 WC:6 Mo.sub.2 C:8 (Ti, Ta, W, Mo) TiN:20 TiC:other (CN):other 16 Co:6 Ni:6 TaC:10 Co:6 Ni:6 0.43 1840 --   1840 --   1640 8/10      0.47 WC:8 Mo.sub.2 C:5 TiN:3 (Ti, Ta, W, TiN:40 TiC:other Mo) (CN):other 17 Co:7 Ni:7 NbC:2 Co:7 Ni:7 0.43 1920 --   1920 --   1660 10/10    0.26 TaC:4 WC:10 (Ti, Ta, Nb, W, Mo.sub.2 C:10 TiN:30 Mo) (CN):other TiC:other 18 Co:8 Ni:10 Co:8 Ni:10 0.36 1840 --   1840 --   1560 7/10      0.33 NbC:5 TaC:5 (Ti, Ta, Nb, W, WC:8 Mo.sub.2 C:8 Mo) (CN):other TiN:30 TiC:other __________________________________________________________________________ __________________________________________________________________________ Substrate Maximum Surface  Hardness               Frank Composition of hard- hardness Hard-                  Wear (% by weight)Blend Composition (% by weight)Substrate ##STR15## (Hv)ness (%)percent (Hv)ness (.mu.m)Depth HardnessInternal ##STR16## (mm)Width __________________________________________________________________________ Comparative Cutting Inserts 19 Co:16 NbC:10 Co:16 TiN:3 0.48 1830 --   1830 --   1650 9/10      0.30 WC:15 TiN:40 (Ti, Nb, W) TiC:other (CN):other 20 Co:10 Ni:12 Co:10 Ni:12 0.49 1770 --   1770 --   1430 6/10      0.56 TaC:5 Mo.sub.2 C:10 (Ti, Nb, W, Mo) WC:8 TiN:35 (CN):other TiC:other 21 Co:12 Ni:6 Co:12 Ni:6 0.28 1880 --   1880 --   1630 8/10      0.29 TaC:10 Mo.sub. 2 C:10 (Ti, Ta, Mo, W) WC:15 TiN:20 (CN):other TiC:other 22 Co:10 Ni:10 Co:10 Ni:10 0.29 1810 --   1810 --   1480 7/10      0.40 Mo.sub.2 C:15 TiN:25 (CN):other TiC:other 23 Co:20 Ni:5 Co:20 Ni:5 0.34 1760 --   1760 --   1420 8/10      0.49 TaC:5 Mo.sub.2 C:5 (Ti, Ta, Mo, W, WC:10 TiN:25 Hf) (CN):other HfC:0.5 TiC:other __________________________________________________________________________

## Claims

1. A blade member for cutting-tools, comprising a substrate of cermet consisting, apart from unavoidable impurities, of: the group consisting of cobalt and nickel; and at least one element selected from the group consisting of tungsten, molybdenum, tantalum, niobium, hafnium and zirconium, said composite carbo-nitride satisfying the relationship of 0.2.ltoreq.b/(a+b).ltoreq.0.7, where a and b denote atomic ratios of carbon and nitrogen, respectively; the maximum hardness is present at a depth between 5 .mu.m and 50 .mu.m from a substrate surface thereof, said substrate surface having hardness of 20% to 90% of said maximum hardness.

2. A blade member for cutting-tools according to claim 1, in which said hard dispersed phase further contains at least one compound selected from the group consisting of tungsten carbide and titanium nitride.

3. A blade member product for cutting tools produced by the process of: element selected from the group consisting of cobalt and nickel for forming a binder phase, the balance being a powder of a carbo-nitride of titanium and at least one element selected from the group consisting of tungsten, molybdenum, tantalum, niobium, hafnium and zirconium, for forming a hard dispersed phase, said composite carbo-nitride satisfying the relationship of 0.2.ltoreq.b/(a+b).ltoreq.0.7, where a and b denote atomic ratios of carbon and nitrogen, respectively; sintering step including effecting initial temperature elevation to 1100.degree. C. in a vacuum, subsequently elevating said temperature from 1100.degree. C. to a temperature ranging between 1400.degree. C. and 1500.degree. C. in a nitrogen atmosphere, and subsequently conducting said sintering operation in a vacuum; to obtain a substrate having a hard surface layer in which a region having maximum hardness is present at a depth between 5 .mu.m to 50 .mu.m from the substrate surface, said substrate surface having a hardness of 20% to 90% of said maximum hardness.

4. The product produced by the process of claim 3 in which said dispersed phase further contains at least one compound selected from the group consisting of tungsten carbide and titanium nitride.