JPS6311645A - Nitrogenous sintered hard alloy and its production - Google Patents

Abstract

PURPOSE:To improve toughness and strength and the crater wear resistance during high-speed cutting by subjecting the double carbonitrides of Ti and transition metal except the specific Ti excluding Mo to a soln. heat treatment at specified ratios of N and C, then sintering the same with Ni and Co. CONSTITUTION:The powders of the respective nitrides, carbides or double carbonitrides of Ti and >=1 kinds of the transition metals except Ti selected from the group IVa, Va, VIa of periodic table excluding Mo are so mixed that the atomic ratio N/(C+N) of N and C attains 0.3-0.6. Such powder mixture is preheated to the sintering temp. or above in an N2 atmosphere and is subjected to the soln. heat treatment; thereafter, the powder mixture is ground to form the powder of the double carbonitrides. The powder of Ni and/or Co is added to and mixed with said powder and the powder mixture is sintered in the N2 atmosphere. The sintered hard alloy in which yellow and double color particles do not exist or exist at <=0.01vol% is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a particularly high toughness nitrogen-containing sintered hard alloy used as a machining tool.

[Conventional technology]

In recent years, sintered hard alloys (cermets) containing nitrogen, which have a hard phase of carbonitride mainly composed of titanium and bonded with a binder phase of nickel and/or cobalt, have been put into practical use as cutting tools.

This nitrogen-containing sintered hard alloy has significantly finer grains in the hard phase compared to conventional sintered hard alloys that do not contain nitrogen and have a hard phase of carbide such as titanium, so it has significantly improved high-temperature creep resistance. As a result, they are being used together with cemented carbide in fields such as cutting tools, where conventional sintered hard alloys that do not contain nitrogen are almost impossible.

However, conventional nitrogen-containing sintered hard alloys (T1, T
a, W, Mo) ((IN) ・Ni~C!o system is the main one, and as stated in Japanese Patent Publication No. 56-51201 etc., molybdenum is present in the intermediate phase between the hard phase and the binder phase. It was considered an essential component because it protects the hard phase from the liquid phase during sintering and suppresses particle growth of the hard phase due to solution precipitation.

However, this conventional nitrogen-containing sintered hard alloy
During the manufacturing process, when heated in vacuum, the carbonitrides contained tend to decompose, so it is inevitable that bores remain after sintering, and the strength tends to be insufficient compared to conventional cemented carbide. This tendency was more pronounced as the nitrogen content increased. Therefore, improvements have been made to sintering methods such as sintering in a nitrogen atmosphere to prevent the decomposition of carbonitrides, but even so, the properties cannot be improved due to segregation of the nitrogen contained and coalescence. It still wasn't enough.

Furthermore, although high-speed cutting has recently been increasingly demanded in the field of cutting tools, nitrogen-containing sintered hard alloys have the disadvantage that crater wear that occurs on the tooth surface of cutting tools is extremely easy to progress during high-speed cutting. . Crater wear is a phenomenon in which the hard phase of a nitrogen-containing sintered hard alloy is excavated in particle units and falls off. Generally, crater wear can be improved by making the structure rougher, but since the rougher the structure, the lower the hardness, this improvement method naturally has its limits.

[Problem that the invention seeks to solve]

In view of such conventional circumstances, an object of the present invention is to provide a nitrogen-containing sintered hard alloy that has improved toughness and strength and has improved crater wear resistance during high-speed cutting as a cutting tool.

[Means for solving problems]

The nitrogen-containing sintered hard alloy of the present invention has a hard phase consisting of a double carbonitride of titanium as an essential component and at least one transition metal other than titanium selected from groups IVa1Va11a of the periodic table, and nickel and / or a binder phase containing cobalt and unavoidable impurities, does not substantially contain molybdenum, and has an atomic ratio N/(C+N) of nitrogen and carbon contained in the entire hard phase of 0.3 to 0.6. Yes, there are no yellow or brown particles, or if there are, 0.01
% by volume or less.

The production of such a nitrogen-containing sintered hard alloy involves the use of titanium nitride,
A carbide or carbonitride powder and a nitride carbide or carbonitride powder of at least one transition metal other than titanium selected from the IVa, Vas and VTa groups of the periodic table excluding molybdenum are combined into a mixture of nitrogen and carbon. Atomic ratio N/ (0+N)
This mixed powder is preliminarily heated above the sintering temperature in a nitrogen atmosphere to undergo solid solution treatment, and then pulverized to obtain a double carbonitride powder. A method is used in which nickel and/or cobalt powder is added and mixed to carbonitride powder and sintered in a nitrogen atmosphere.

In the present invention, "contains substantially no molybdenum" means that it is not actively added as a component of the hard phase, and therefore, molybdenum in the entire nitrogen-containing sintered hard alloy, including molybdenum mixed in during the manufacturing process, is 1. If it is less than % by weight, desirable properties can be obtained and therefore it is acceptable.

In addition, the nitrogen-containing sintered hard alloy may contain unavoidable impurities such as iron mixed in during the manufacturing process to the extent that the properties are not affected, and the raw material powder may be used to improve sinterability as is usually done. To achieve this, a small amount of carbon powder, generally 0.01 to 2.0% by weight, can be mixed.

[Effect]

(Ti, Ta, WSMO) ((!N) “Ni~C
In order to study crater wear on iO-based conventional nitrogen-containing sintered hard alloys, we created cracks with an indenter of a Vickers hardness tester and investigated the propagation path. As a result, we found that an intermediate layer between the hard phase and the binder phase It was confirmed that the crack was propagating. Therefore, it is thought that crater wear resistance can be improved by removing the intermediate phase, but since this intermediate phase is mainly composed of molybdenum carbonitride, as mentioned above, if molybdenum is eliminated, the particles will become coarser. However, there is a contradiction in that desired characteristics cannot be obtained due to a decrease in hardness.

Regarding the segregation of nitrogen in conventional nitrogen-containing sintered hard alloys, it has been found that yellow or brown particles can be observed in the hard phase structure using an optical microscope, and that these yellow or brown particles are mainly titanium nitrides. It is a carbonitride, and as long as these particles appear, bores are likely to occur due to decomposition in areas with a high concentration of nitrogen, and in areas with a low concentration, the effects of nitrogen content may not be fully exerted, resulting in deterioration of properties. I also understood.

Therefore, as a result of various studies, in the present invention, a double carbonitride of titanium and at least one transition metal other than titanium selected from groups ①a, V2L, and Vla of the periodic table is formed in advance by solid solution treatment. By using this double carbonitride powder, mixing it with other nickel powder, etc. as usual and sintering it, the hard phase particles and the surrounding structure can be separated without causing coarsening of the particles even if they do not contain molybdenum. It becomes possible to improve adhesion, and at the same time, it is possible to uniformly disperse nitrogen, and as a result, the yellow to brown particles that are conventionally seen are eliminated. Further, the carbide or carbonitride of the Va group element as a raw material also exhibits a yellow or brown color, but the yellow or brown particles disappear by the solid solution treatment. Incidentally, even if yellow or brown particles are present, if the amount is 0.01% by volume or less, an effect of improving strength and toughness can be obtained.

The atomic ratio of nitrogen and carbon in the entire hard phase, N/(C+N), is 0.
．． The reason why it is limited to the range of 3 to 0.6 is that if it is less than 0.3, the toughness will decrease, if it exceeds 0.6, the sinterability will decrease and nitrogen will be likely to segregate, and if it is more than 0.7, it will become yellow or brown. particles will always be generated.

Furthermore, since the double carbonitride constituting the hard phase has a small amount of solid solution in the binder phase, for the purpose of solid solution strengthening of the binder phase, metallic titanium and/or tungsten powder is mixed with the powder before sintering. The properties can be further improved by solidly dissolving titanium or tungsten in nickel and/or cobalt in the binder phase.

Furthermore, when nickel and cobalt are used simultaneously as a binder phase, the weight ratio of nickel and cobalt N i / (N i + o
o) is preferably in the range of 0.3 to 0.8.

A higher ratio is preferable; however, if it exceeds 0.8, the hardness decreases, and if it is less than 0.3, no improvement in crater wear resistance due to increased interfacial strength can be obtained.

Further, a small amount of Zr is contained in the nitrogen-containing sintered hard alloy of the present invention.

It may contain y, ar, Az, etc., and the effects of the present invention can also be achieved in that case.

〔Example〕

Example 1 After mixing commercially available T1 (N) powder with an average particle size of 2 μm and TaO powder and WC powder with almost the same particle size in a ball mill, the mixture was mixed with a nitrogen gas stream with a nitrogen partial pressure of 400 torr at 170 torr.
After solid solution treatment at 0 C for 1 hour, double carbonitrides were formed.
0.88Ta0.05WO,,07)(C0,52N0
．． 48) was formed. This double carbonitride is O/ (0+N
) = 0.48, and it was confirmed by X-ray diffraction that the TaC and we peaks had disappeared.

After pulverizing this double carbonitride with a ball mill, the powder 8
N1 powder 7.9% by weight and co powder 7% by weight in 5-layer plate %
(Ni/ (Ni+Oo) = 0.53) and 0.1% by weight of free carbon were added and mixed, and 3% by weight of camphor was added to the mixed powder and molded by molding. This molded body was heated at 14,500 in a nitrogen stream with a nitrogen partial pressure of 10 torr.
Cermet A was produced by time sintering.

For comparison, double carbonitride powder 8 formed in the same manner as above
0% by weight, 5% by weight of MoC powder and N1 as above.
Powder, CO powder, and free carbon powder were added and the thermets) E? were added under the same conditions. B-built.

In addition, the same T1 (a N) powder, TaO powder, and weC powder as above were mixed with N1 powder, COC powder, and free carbon powder without solution treatment, and the same as Cermet A) was prepared under the same conditions. A cermet C with the composition is manufactured, and further M
o C powder was added to produce Cermet D having the same composition as Cermet B).

The structure of each cermet was polished to a mirror surface and was examined using an optical microscope (15
When observed at a magnification of 0.00 times), the presence of independent yellow or brown particles in the hard phase that was clearly different from the color tone of the fabric was confirmed in thermets) A and B.
did not exist.

Furthermore, for each cermet, the hardness (Hv), fracture toughness (K), and strength (kg/fnm) were measured, as well as the crater wear depth and flank wear amount under cutting condition 1 in Table 1. Measure the chip breakage rate under cutting condition 2,
The results are shown in Table 2. From Table 2, it can be seen that the thermet A of the present invention has excellent toughness and wear resistance, and also has high strength and hardness.

Example 2 Cermets of Samples 1 to 10 in Table 3 were produced in the same manner as Cermet A or Cermet C of Example 1. However, N/(C+N) of the double carbonitride formed was changed by changing the ratio of carbon and nitrogen in the T i (ON) powder.

For each sample, the characteristics, crater wear depth and flank wear amount under cutting condition 1 in Table 1, and chip breakage rate under cutting condition 2 were measured in the same manner as in Example 1, and the results are shown in Table 4. Indicated. It can be seen from Table 4 that the cermet of the present invention has excellent toughness and strength, as well as excellent wear resistance and crater resistance.

Furthermore, when the structure of each sample was observed using an optical microscope (1500x magnification) in the same manner as in Example 1, yellow to brown particles were confirmed in Samples A6.7 and 8.

(Note) The × in the sample is a comparative example.

Example 3 Volume fraction of binder phase and N i / of cermet A of Example 1
(Without changing the Ni+(!O) ratio, the metal W powder was
Cermets) E in which 1% by weight of metal T1 powder was added and dissolved in the binder phase, and Cermets) F in which 1% by weight of metal T1 powder was added and dissolved in the binder phase were produced in the same manner.

When a cutting test was conducted for each cermet under cutting conditions 3 in Table 1, the amount of deformation of the cutting edge was found to be cermet A.
were Q, Q5+++m, whereas thecermets) E and F were 0.03mM, proving that the solid solubility properties of W and T1 in the bonded phase were improved.

〔Effect of the invention〕

According to the present invention, it is possible to provide a nitrogen-containing sintered hard alloy that is excellent in crater wear resistance during high-speed cutting and has high toughness and high strength as a cutting tool.

Applicant: Sumitomo Electric Industries, Ltd. ,・,↑・=,

Claims (5)

[Claims] (1) Titanium, an essential component, and IVa and Va of the periodic table
, a hard phase consisting of a double carbonitride with at least one transition metal other than titanium selected from Group VIa, and a binder phase containing nickel and/or cobalt and unavoidable impurities, and substantially contains molybdenum. The atomic ratio N/(C+N) of nitrogen and carbon contained in the entire hard phase is from 0.3 to
0.6, and has no yellow or brown particles, or if present, the amount is 0.01% by volume or less. (2) The nitrogen-containing sintered hard alloy according to claim (1), characterized in that metallic titanium and/or tungsten are dissolved in nickel and/or cobalt in the binder phase. (3) Claim (1) or (2) characterized in that the binder phase is made of nickel and cobalt, and the weight ratio of both Ni/(Ni+Co) is 0.3 to 0.8.
) The nitrogen-containing sintered hard alloy described in item 1. (4) titanium nitride, carbide or carbonitride powder;
Nitride, carbide, or carbonitride powder of at least one transition metal other than titanium selected from groups IVa, Va, and VIa of the periodic table excluding molybdenum, and the atomic ratio of nitrogen and carbon is N/(C++). Mix so that the ratio is 0.3 to 0.6,
This mixed powder is preliminarily heated in a nitrogen atmosphere and subjected to solid solution treatment, and then pulverized to obtain a double carbonitride powder. Nickel and/or cobalt powder is added and mixed to this double carbonitride powder, and nitrogen A method for producing a nitrogen-containing sintered hard alloy, characterized by sintering in an atmosphere. (5) The weight ratio of nickel and cobalt powder is Ni
The method for producing a nitrogen-containing sintered hard alloy according to claim (4), characterized in that the addition and mixing are carried out so that /(Ni+Co) is 0.3 to 0.8.