JPH03197603A - Manufacture of high density titanium alloy sintered parts - Google Patents

Abstract

PURPOSE:To obtain the parts having excellent fatigue strength without ruggedness of surface and defect of penetrating hole-state by executing hole sealing treatment for pressurized green compact with metal plating of Ni, etc., at the time of manufacturing the Ti alloy parts with raw powder method. CONSTITUTION:Mixed powder mixing Ti powder and one or more kinds of metal powder so as to be the prescribed alloy components, is packed into a flexible mold of rubber, etc., and cold isostatic pressing is executed to obtain the powder green compact. After executing be hole sealing treatment by executing Ni, Cu, Co or Cr plating on surface of this green compact at 10-500mum plating thickness, hot isostatic pressing is executed to obtain the high density Ti alloy sintered parts. As the other way, after executing be above plating to the sintered body obtd. by sintering the powder green compact, the hot isostatic pressing may be executed. By mis method, the parts having complicate shape are easily obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) This description relates to sintered parts for automobile parts, marine or ship parts, shell structures, etc., and in particular to the production of high-density titanium alloy sintered parts. Regarding the method.

(Prior Art) Automotive engine parts with complex shapes, such as connecting rods, have conventionally been manufactured by cutting steel materials. In line with recent objectives such as improving fuel efficiency, reducing weight, and increasing efficiency, various parts are being developed using titanium alloy materials instead of steel materials. Similar developments are also underway in marine and ship components and shell structural components.

However, conventional titanium alloy parts are first melted in a vacuum arc melting furnace (VAR), then forged, hot rolled,
After going through various processes such as heat treatment, it is manufactured by mechanical processing, and because the process is expensive and complicated, the product price is inevitably high, and it is difficult to use it as a general-purpose automobile part. Ta.

Currently, in order to solve the above-mentioned problems, near-net-shave molding such as powder metallurgy is being used instead of conventional melting. Among the powder metallurgy methods, a mixed powder that is mechanically mixed in advance to form a predetermined alloy component is filled into a flexible mold made of rubber or other material so that it can be molded into a predetermined shape, and cold isostatic pressing is performed. There is a method for manufacturing titanium alloy parts using the so-called raw powder method, which is compacted into a predetermined shape using (CI P), then sintered by heat treatment at high temperatures, and then hot isostatically pressed (HI P). It is being developed.

According to the above method, it is possible to manufacture automobile parts and the like without going through elaborate processes such as melting, forging, or hot rolling. In addition, the additional component elements of titanium alloy can be easily blended in any weight ratio, and although they cannot be added due to solidification segregation in the melting method and alloy powder method, there is a limit to the amount of addition. There is also the advantage that elements can also be added.

However, it is becoming clear that this raw powder method has the following problems. First, since a flexible mold such as a rubber mold is used during CIP, unevenness due to the powder shape remains on the surface of the powder compact, and after sintering and H
Similar unevenness remains on the surface after IP. Second, CI of non-homogeneous filling or complex-shaped products when filling powder into molds.
Due to the local uneven pressure that occurs during P, through holes are partially formed on the surface of the powder compact after sintering, and H
As pressure medium gas flows into the IP treatment process, pressure acts on the through hole, resulting in insufficient sealing of the through hole, and the through hole remains as a defect after the HIP treatment. Therefore, it may not be able to withstand use as automobile parts that require high fatigue strength.

Conventionally, countermeasures such as grinding after HIP treatment have been taken, but it is not only difficult to grind components with complex shapes by machining, etc., but it also reduces the characteristics of the base powder method, and is also disadvantageous in terms of cost. Therefore, a rational solution to this problem is desired.

As a method to solve the above problems, JP-A-62-20
In Japanese Patent No. 520, a pressure-molded body is subjected to a pore-sealing process by shot blasting, and then a HIP process is performed. However, with this method, it is difficult to seal the complex-shaped sintered body surface, especially the inner wall surface.

On the other hand, in JP-A-1-159358, the wear resistance and fatigue strength of the titanium member are improved by applying electroless plating to the surface of the titanium member, annealing it, and then subjecting it to shot peening. This is a treatment for titanium members with smooth surfaces, and cannot be applied to sealing defects on the surface of parts molded with powder as in the present invention, and is essentially different from the present invention. .

(Problems to be Solved by the Invention) The present invention applies sealing treatment before HIP treatment, and from this, sintered parts for automobile parts, marine or ship parts, and general structural use, especially high-density titanium alloy. It is an object of the present invention to provide a manufacturing method for obtaining a part having excellent fatigue strength and having no irregularities or defects such as through holes on the surface of a sintered part.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a predetermined alloy using a mixed powder obtained by mixing titanium powder and one or more metal powders so as to have a predetermined alloy component. A mold is filled with a mixed powder mixed to match the components, and Ni, Ni, The gist of the present invention is a method for manufacturing a high-density titanium alloy sintered part, which is characterized by applying Cu, Co, or Cr plating to perform a sealing treatment, and then hot isostatic pressing.

(Function) In the method of the present invention, a mixed powder prepared by mechanically mixing in advance to form a predetermined alloy component is filled into a flexible mold made of rubber or the like, and a predetermined amount is formed using a cold isostatic press. A powder compact that has been molded into a shape and has an uneven surface and through-holes on the entire surface, or a powder compact that has been sintered by heat-treating the powder compact at a high temperature, and has an uneven surface and localized through-holes. By plating the surface of any of the sintered bodies in which this has occurred, the powder compact or the surface layer of the sintered body is smoothed and the through holes are closed. This makes it possible to reduce surface irregularities, prevent pressure medium gas from flowing into the through holes during the HIP process, and eliminate the through holes during the HIP process. This has made it possible to significantly improve the unevenness and local defects in the form of through-holes in the sintered body after HIP treatment, which were conventional problems.

In the present invention, metal powder refers to single powder such as aluminum powder and vanadium powder, and alloy powder such as V40Aρ6o.

In addition, in the present invention, the plating thickness is limited to 10-500 or more because plating less than 10-100 is insufficient for sealing, and plating 500 or more is not sufficient to seal the pores and the surface. This is because not only does it not contribute to alleviating unevenness, but it also has the disadvantage of unnecessarily increasing the density of the sintered body.

The present invention will be explained in detail below.

Example 1 2N type powder, i.e. its composition is 99.6% titanium
, titanium powder containing 0.09% oxygen and 0.0005% or less chlorine, and a master alloy powder for addition whose composition was 60% aluminum and 40% vanadium were prepared.

Next, a product having a Tl-6AfI-4v composition was manufactured according to the following steps. First step: Titanium powder and additive master alloy powder were mechanically mixed at a weight ratio of 9:1. Second step: The mixed powder obtained in the first step was charged and filled into an elastic rubber mold having a predetermined shape. Third step: The filled powder was compacted by cold isostatic pressing. Fourth step: The green compact is heated to a vacuum degree of 10-' to 1O-
The sintering process was carried out at a temperature of about 1100°C. The relative density of the obtained sintered body was 92%. Fifth step: The surface of the sintered body was plated by a known electroplating method.

Sixth step: The plated sintered body was subjected to hot isostatic pressing at a temperature of about 900°C.

Table 1 shows the type of plating, the main bath composition, the average plating thickness, the sealing condition after plating, the relative density after HIP, and the fatigue strength of the finished product. The fatigue test conditions in the table are axial force, stress ratio R--1, frequency f-20Hz, atmosphere, and room temperature.

1 As is clear from Table 1, N 1. Cu, Co,
It can be seen that as a result of complete pore sealing treatment in both cases of Cr, a product with higher density is obtained, the surface has fewer irregularities, and the fatigue strength is improved compared to the conventional manufacturing method.

Example 2 Class 2a powder, i.e. its composition is 99.6% titanium
, sponge titanium powder consisting of 0.09% oxygen and 0.0005% or less chlorine, and its composition is 60% aluminum,
A master alloy powder for addition containing 40% vanadium was prepared.

Then, a product having a composition of TI-6Tl-6A was manufactured according to the following steps. First step: Titanium powder and additive master alloy powder were mechanically mixed at a weight ratio of 9:1. Second step: The mixed powder obtained in the first step was charged and filled into an elastic rubber mold having a predetermined shape. Third step: The filled powder was compacted by cold isostatic pressing. Fourth step: The surface of the second compacted powder compact was plated by a known electroplating method. Fifth step: The plated sintered body was subjected to hot isostatic pressing at a temperature of about 900°C.

Table 2 shows the type of plating, the main bath composition, the average plating thickness, the sealing condition after plating, the relative density after IIIP, and the fatigue strength of the finished product. The fatigue test conditions in the table are axial force, stress ratio R--1, and frequency f = 20Hz.

In the atmosphere, at room temperature.

As is clear from Table 2, Nl, Cu, and Co.

It can be seen that as a result of complete pore sealing treatment in both cases of Cr, a product with higher density is obtained and the surface unevenness is reduced compared to the conventional manufacturing method.

(Effects of the Invention) As is clear from the above description, the present invention can easily eliminate surface irregularities and through-hole-like defects, which are problems in the production of titanium alloy sintered parts using the raw powder method, without grinding. It is possible to obtain high-density titanium alloy parts that can withstand automotive parts and the like while maintaining the characteristics of the base powder method.

Claims (2)

[Claims] (1) The surface of a powder compact obtained by filling a mold with a mixed powder made by mixing titanium powder and one or more metal powders to have a predetermined alloy composition, and then cold isostatically press-forming the mixed powder. A method for producing a high-density titanium alloy sintered part, characterized in that the pores are sealed by applying Ni, Cu, Co, or Cr plating to a plating thickness of 10 μm or more and 500 μm or less, and then hot isostatic pressing. (2) Fill a mold with a mixed powder made by mixing titanium powder and one or more metal powders to have a predetermined alloy composition, and then cold isostatically press the mixture to form a powder compact. Then, the surface of the titanium alloy sintered body produced by sintering the powder compact is sealed by applying Ni, Cu, Co, or Cr plating to a thickness of 10 μm or more and 500 μm or less, and then hot plated. A method for manufacturing high-density titanium alloy sintered parts, characterized by hydrostatic pressing.