JPH08144004A - Cermet alloy - Google Patents

Abstract

PURPOSE: To improve the wear resistance and fracture toughness of a cermet alloy by imparting a compsn. consisting of a solid soln. contg. a transition metal, carbon and nitrogen and having a B1 type crystal structure, a bonding phase contg. an iron family metal and a very small amt. of Al. CONSTITUTION: This cermet alloy consists of 80-95wt.% solid soln. contg. at least one of transition metals belonging to the groups IVa, Va and Va, carbon and nitrogen and having a B1 type crystal structure, 5-20wt.% bonding phase contg. at least one of iron family metals, 0.002-0.0001wt.% Al and inevitable impurities. The cermet alloy has improved fracture toughness and wear resistance because it contains such a very small amt. of Al.

Description

Detailed Description of the Invention

[0001]

This invention relates to cermet alloys,
In particular, the present invention relates to a cermet alloy which is excellent in heat crack resistance and strength and can be preferably used in a cutting tool.

[0002]

2. Description of the Related Art Cemented carbides and cermet alloys generally used as cutting tools are required to have excellent properties such as heat crack resistance, oxidation resistance, high temperature hardness and fracture toughness. However, conventional cermet alloys used for cutting tools are generally inferior in heat crack resistance and fracture toughness as compared with cemented carbides. Further, the cermet alloy is generally inferior in wear resistance as compared with the surface-coated cemented carbide.
In order to ameliorate these weaknesses in cermet alloys, many researchers have made various efforts for cermet alloys.

For example, in JP-A-63-11645 and JP-A-63-11630, it has been attempted to improve toughness by incorporating nitrogen into a cermet alloy. Also, JP-A-61-212989 and JP-B-6
1-1506, Japanese Patent Publication 1-333289 and Japanese Patent Publication Sho 63
-39649 attempts to improve the properties of cermet alloys by including aluminum.

[0004]

By the way, in recent years, cutting conditions have become severer year by year in order to improve production efficiency.
Further improvements in various physical properties of cutting tools are required. For example, even in the cermet alloy containing nitrogen or aluminum as described above, sufficient wear resistance or the like cannot be ensured in high-speed cutting, and the present situation is that the cutting tool has a short life. .

In view of the current state of the prior art, it is an object of the present invention to provide a cermet alloy having improved physical properties such as wear resistance and fracture toughness.

[0006]

The cermet alloy according to the present invention contains at least one of transition metals included in groups 4A, 5A and 6A of the periodic table, carbon and nitrogen, and has a B1 type crystal structure. 80-95% by weight with
A solid solution of; and containing at least one of the iron group metals 5
.About.20% by weight of a binder phase; 0.002 to 0.0001% by weight of aluminum; and unavoidable impurities. The B1-type crystal structure means so-called N
It represents an aCl type crystal structure.

[0007]

In the cermet alloy of the present invention,
Since it contains a small amount of 002 to 0.0001% by weight of aluminum, it is possible to obtain a cermet alloy with improved fracture toughness and wear resistance. When the aluminum content is 0.0001% by weight or less, no influence on the properties of the cermet alloy is observed, and conversely, when the aluminum content exceeds 0.002% by weight, the fracture strength is rather high. It tends to decrease.

[0008]

【Example】

[0009]

[Table 1]

Cermet alloy samples A to L having the compositions shown in Table 1 were prepared by the following method. Here, the sample is analyzed by a wet analysis method or ICP.
-Using the MS method etc. The minus sign in Table 1 indicates that the content is 0.0001% by weight or less.

First, various carbide powders, nitride powders, carbonitride powders, (Ti, M) CN powders, Co powders, Ni powders, and Al powders were prepared as raw material powders. Here, M represents a metal element other than Ti.
A mixed powder containing these powders in a required ratio was uniformly mixed by wet mixing for 18 hours. Thereafter, the mixed powder was press-molded at a pressure of 1 ton / cm ² and made into a cermet alloy by sintering in vacuum at a temperature of 1490 ° C. for 1 hour.

The thus-sintered cermet alloy was cooled to room temperature, and then processed into a shape of a throw-away tip SNGA120408, which is a replaceable cutting edge of a cutting tool, with a diamond grindstone. A continuous cutting test was performed on these throw-away tips under the following cutting conditions, and the flank wear amount was measured and the state of the cutting edge was observed.

Workpiece material: Round bar of alloy steel SCM435 (Brinell hardness HB = 245) Cutting speed: 195 m / min Bit feed: 0.25 mm / rotation Depth of cut: 1.5 mm Cutting time: 5 minutes Cutting oil: Water-soluble oil

[0014]

[Table 2]

The results of the continuous cutting test as described above are shown in Table 2. As can be seen from Table 2, the wear amount on the flank of the throw-away tip does not show a large difference in any of the samples A to F, but regarding the state of the cutting edge,
It was observed that in samples A to I belonging to the scope of the present invention, normal wear and thermal cracking were minute, but in samples J to L which are outside the scope of the present invention, defects or cutting edges due to thermal cracking at the cutting edge were observed. Wreck was observed.

Further, an intermittent cutting test using a square bar was carried out under the following cutting conditions, and the number of defective cutting edges after the test among the 10 cutting edges was measured.

Work Material: Square bar of alloy steel SCM435 (Brinell hardness HB = 245) Cutting speed: 135 m / min Bite feed: 0.4 mm / rotation Depth of cut: 2.0 mm Cutting time: 2 minutes Cutting oil: None Table 2 also shows the results of various square cutting tests. As can be seen from Table 2, Samples A to I belonging to the present invention
In all of the samples, the number of defective cutting edges after the test was 10 or less out of 10 of the number of test cutting edges, but for samples J to L, which are out of the scope of the present invention, The number of defective cutting edges after the test was 7 or more, which shows that the improvement by the present invention is remarkable.

In the cermet alloy according to the present invention, the solid solution having a B1 type crystal structure may further contain a small amount of oxygen or boron. Needless to say, a coating film formed by CVD or PVD may be formed on the surface of the cermet alloy according to the present invention. Further, it goes without saying that the working surface of the cermet alloy may be a sintered surface or a processed surface with a diamond grindstone or the like. Furthermore, Al added to the raw material powder may be in the form of a compound when compounded.

[0019]

As described above, according to the present invention, it is possible to provide a cermet alloy excellent in heat crack resistance and impact resistance. In particular, the cermet alloy is preferably used as a cutting edge of a cutting tool. I will get it.

Claims (1)

[Claims] 1. 80 to 95 containing at least one of transition metals contained in groups 4A, 5A and 6A of the periodic table, carbon and nitrogen, and having a B1 type crystal structure.
5% to 20% by weight of solid solution containing at least one of iron group metals
A cermet alloy containing the binder phase of 0.002 to 0.0001% by weight of aluminum and inevitable impurities.