JPS63169341A - Production of morybdenum based alloy dispersed with carbide and strengthened thereby - Google Patents

Abstract

PURPOSE:To produce a Mo based alloy having the low amount of oxidation, high density and excellent mechanical strength by mixing carbide forming elements and a source of carbon for deoxidation each in the form of carbide into a Mo material, then executing compacting and executing vacuum sintering. CONSTITUTION:The carbide forming elements are added into Mo or Mo alloy powder of matrix components in the form of TiC, ZrC, etc., and furthermore the source of carbon for deoxidation is added therein to mix with. Said mixed powder is subjected to compacting and sintered in a vacuum. The Mo group alloy dispersed with the carbide and strengthened thereby, and having the low amount of oxidation and the mechanical strength is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION As already mentioned, the object of the present invention is a carbide dispersion strengthened molybdenum-based alloy, which is characterized by a Mi weave in which carbides are dispersed in a molybdenum or molybdenum alloy matrix. As a molybdenum alloy as a matrix, M
A heat-resistant alloy such as an alloy of O and at least one of high melting point metals such as W, Co, Ta, Nb, and Re is used. The carbide includes one or more carbides of carbide-forming elements such as TI%Zr and Hf%Nb.

The present invention provides raw material powder for molybdenum or a molybdenum alloy matrix component (i.e., molybdenum powder when the matrix is molybdenum, molybdenum powder, ten-alloy element powder, or the alloy powder when the matrix is a molybdenum alloy), Ti, Tic, Zr and other carbide-forming elements such as Zr
The main point is to add a carbon source for deoxidizing oxygen contained in the form of a carbide such as C and mainly in Mo as a matrix component, generally in the form of a carbide of molybdenum. When the matrix is a molybdenum alloy, it is also possible to add a total element that makes it fi in the form of a carbide, and use part or all of the carbon as a carbon source for deoxidation.

In the following description, TZM (Mo-α4~α55vt
%Ti-0.06~0.12vt%Zr-αo1~α0
Let's proceed by taking 4vt%C) as an example.

Mo raw material powder, TiC and ZrC powder, and Mo carbide (
M o C, M o z C) are added and mixed using a V-type mixer or the like. TiC and ZrC are the target TZ
It is added as a composition amount of M alloy. MoC (MolC)
The carbon content and 0ffi in Mo powder are Cl0 in atomic ratio.
=1 to t5. The amount of carbon that contributes to deoxidation is the same as that supplied by Mo carbide (this means that the carbon that actually contributed to deoxidation originates entirely from Mo carbide). I don't mean that. Tl.

Since Zr and the like are supplied in the form of carbides and ultimately used as carbides, it is safe to assume that only the carbon in the Mo carbide contributes to deoxidation based on stoichiometry. ).

The effect of using carbide powder also occurs in the mixing stage. When using carbon powder as in the past, it was difficult to mix uniformly using a V-type mixer because the specific gravity of the carbon powder was smaller than the molybdenum powder, which is the main component.However, using carbide powder This allows relatively uniform mixing, thereby shortening the mixing time.

The mixed powder is compacted using a mold press or the like. By using carbide powder instead of carbon powder, compaction properties are significantly improved. - According to the example, the density was about 5% higher and the transverse rupture strength was about twice as high as the conventional example. Obtaining a high-quality green compact is essential for obtaining a high-density sintered compact in the subsequent sintering process, and this is where the baby face of the present invention, which avoids the use of carbon powder, exists.

Next, the powder compact is vacuum sintered. Preferably, the sintering includes a preliminary sintering step in which gas is sufficiently released by a desanding reaction in a temperature range in the carbon reduction region of c-1-o→CO and in which sintering does not proceed much, and then a pre-sintering step in which the mixed coal is further added. The process is divided into a main sintering stage in which the main sintering process is performed. If sufficient degassing is not performed, pores will remain inside the sintered body, leading to a decrease in the density of the sintered body. Pre-sintering step is 1300 ~ 180 ℃ under vacuum below 10''1 torr.
The main sintering step is carried out by holding at 0"C for 1 to 3 hours and the main sintering step is carried out by holding at 1900 to 2050C for 4 to 8 hours. If the temperature is too high, the vapor pressure of the carbide increases and Causes compositional changes.

Or, conversely, it is also possible to utilize this evaporation to adjust excess carbon in the starting material.

In any case, deoxidation proceeds sufficiently during vacuum sintering. While the dissolution method typically leaves 500 ppm of oxygen remaining, the present invention provides deoxidation to levels well below that level.

At the same time, the density increases by sintering to a level exceeding 90% of the theoretical value, producing a high-density sintered body that can be subjected to subsequent heat treatment without any problems.

Effects of the invention By eliminating the contamination of elements other than the constituent components as much as possible, we have succeeded in producing a high-density sintered body with a low oxygen content, and we have succeeded in producing a molybdenum-based sintered body with mechanical properties comparable to or superior to that of molten products using the powder metallurgy method. This paved the way for the manufacture of alloys.

〔Example〕

TI was added to Mo powder with an oxygen content of approximately 1500 ppm.
C powder α6vt%, ZrC powder α09wt%, furthermore, this M
In order to remove oxygen in o powder by C reduction, MoC powder was
5 vt% was added and mixed. 3 tons of this mixed powder
When compacted at a pressure of n/6n”, the green compact density was:
The density was 65% of the theoretical density. Further, the transverse rupture strength of this green compact was approximately 16 kg'/mm2. Next, this green compact was heated at 170"C in a vacuum of 10-' torr or less.
By heating the powder to a temperature of 100.degree. C. and holding it for 2 hours, oxygen in the green compact was removed by C reduction. Thereafter, sintering was performed by heating the temperature to 2000° C. and maintaining it for 8 hours. The density of the resulting sintered body was 92% or more. Additionally, the amount of oxygen decreased to 140 ppm.

[Comparative example]

The same amounts of TiC and ZrC powders as above were added to the Mo powder. Also, carbon black 0.2v instead of MoC powder
t% was used and mixed. When this mixed powder was compacted under the same conditions as above, the compacted powder density was 60% and the transverse rupture strength was α55 kyf/mrn''.Furthermore, vacuum heat treatment and sintering were performed under the same conditions as above. As a result, the density of the sintered body was 90%, and the oxygen content was 300 ppm.

1・'-1 Name of agent Motohiro Kurauchi 1", 1 Procedural Amendment April 70, 1988 Commissioner of Patents Kuro 1) Indication of Akio Case Patent Application No. 190 of 1988 Person making the amendment Relationship to the case Respondent applicant name Nippon Mining Co., Ltd.

Claims (1)

[Claims] 1) When producing a carbide dispersion strengthened molybdenum-based alloy by a powder metallurgy method, a carbide-forming element is added in the form of a carbide to molybdenum or a raw material powder for a molybdenum alloy matrix component, and a carbon source for deoxidation is added in the form of a carbide of the matrix component. A method for producing a carbide dispersion-strengthened molybdenum-based alloy, which comprises adding and mixing the resulting mixed powder, compacting the resulting powder compact, and vacuum-sintering the compacted compact afterward.