JPH03215603A - Manufacture of high density titanium alloy powder sintered product - Google Patents

Abstract

PURPOSE:To manufacture a high density Ti alloy powder sintered crystal having excellent fatigue strength by executing reduced pressure plasma thermal spraying of the specific metal to surface after compacting and sintering mixed powder of Ti powder and the other metal powder and further executing hot isostatic pressing. CONSTITUTION:The Ti powder and e.g., powder of Al-V alloy are mixed, and after packing into an elastic rubber mold having the specific shape, cold isostatic press-compacting is executed. After sintering the green compact, the sintered body is inserted into the reduced pressure plasma thermal spraying apparatus and one kind of metal among Cu, Ni, Co, Fe, Mn, etc., is thermally sprayed in the reduced pressure atmosphere of Ar, He, etc., to form the thermal spraying film on the surface of sintered body. Successively, the hot isostatic pressing treatment is executed to this to manufacture the sintered parts with the high density Ti alloy powder having excellent fatigue characteristic without developing opened holes on the surface as effect of the sintered body.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing powder sintered parts for automobile parts, marine or ship parts, general structural use, etc. using high-density titanium alloy parts. be.

(Prior Art) Automotive parts with complex shapes, such as connecting rods for engine parts, have traditionally been forged and machined from steel materials. In recent years, various parts have been developed using titanium alloy materials instead of steel materials to improve fuel efficiency and reduce weight. Similar developments are also active in powder sintered parts for marine or ship parts and general structural use.

However, conventional titanium alloy parts are manufactured into thin plates or thick plates after going through processes such as manufacturing ingots using vacuum arc melting, forging, hot rolling, and heat treatment, and then are forged into the desired parts mentioned above. Although it is manufactured by cutting, there are many manufacturing and processing steps, and therefore the product value is high, making it difficult to use it as a general-purpose part. Furthermore, titanium alloys have disadvantages such as poor machinability compared to steel materials.

In order to improve the above points, a powder metallurgy method near net shape (Near N
Efforts are being made to reduce costs by molding using et shape technology. However, even with this powder metallurgy method, many through holes remain on the product surface after the final process of hot isostatic pressing (HIP), making it difficult to withstand use as automotive parts that require high fatigue strength. be.

In order to solve such problems, Japanese Patent Application Laid-Open No. 6220520
The publication discloses that a pressure-molded body is subjected to a pore-sealing process by shosotopeening and then subjected to a HIP process. However, with this method, it is difficult to seal the complex-shaped sintered body surface, especially the inner wall surface.

-X, JP-A-1-159358 discloses that defects on the surface of a sintered body are improved by applying electroless plating to the surface of a titanium member and subjecting it to shot pinning after annealing. Some problems remained.

(Problems to be Solved by the Invention) In order to solve these problems, the inventors of the present invention investigated the elementary powder mixing method among the powder metallurgy methods.

The raw powder mixing method involves mechanically mixing powders of a specified alloy component as raw material powders, filling the mixed powder into a mold made of rubber or the like made in advance into a desired mold, and pressing it into the specified shape using a cold isostatic press. The process of forming the powder into the shape of , then inserting the powder lump into a vacuum sintering furnace, heating it, and forming the alloyed sintered titanium alloy member using hot isostatic pressing (hereinafter referred to as HIP). is a typical example. In addition, if powder is used as a starting material, small lots and a wide variety of products can be easily produced in the final product shape (Ne
t Shape) or a shape close to the final product (Near
It has the advantage that it can be molded into a net shape.

Another major feature of the powder metallurgy method is that there are no internal defects such as polarization formed in the ingot, and desired alloy components can be easily obtained. In order to eliminate surface defects of products after HIP treatment, the present inventors achieved improvement in fatigue properties by shot peening after HIP treatment and disclosed this in Japanese Patent Application No. 1-514.
A patent application has been filed for No. 48. It has been revealed that titanium alloys manufactured by the raw powder mixing method exhibit tensile and fatigue properties that are almost equivalent to those manufactured by the ingot melting and rolling method.

Furthermore, the present inventors have been studying methods for increasing density in the previous process, and have found that it is extremely effective to subject the sintered body to plasma treatment before HIP treatment.

That is, the present invention eliminates through-hole defects on the surface of powder sintered parts, especially titanium alloy sintered parts, for automobile parts, marine or ship parts, and general structural use, etc., by treatment before HIP treatment, increases the density, and improves fatigue strength. The purpose of this invention is to provide a method for manufacturing excellent parts.

(Means for Solving the Five Problems) In order to achieve the above object, the present invention fills a mold with a mixed powder obtained by mixing titanium powder and one or more metal powders so as to have a predetermined alloy composition, One element of Cu, Ni Co Fe, and Mn is deposited on the surface of the titanium alloy sintered body by cold isostatic press molding and sintering of the powder compact, and then hot isostatic press is applied. The summary is a method for manufacturing a high-density titanium alloy powder sintered product, which is characterized by pressing.

The present invention will be explained in detail below.

In the present invention, as the titanium alloy, Tj is, for example, A,
It can be applied to titanium alloys containing one or more of Q, V, Mo, Cr, Zr, Sn, Fe, etc.

In the present invention, metal powders include simple powders such as AΩ powders and VΩ powders.
Refers to alloy powder such as 4oAΩ6o.

Further, in the present invention, the metals Cu, Ni, Co, and FeMn are limited because the metals to be deposited easily form a solid solution with TI, that is, these metals have eutectic temperatures with TI of 875, 942, and 1020, respectively. 1085. 1
This is because the temperature is as low as 180°C. In addition, when the above metals are deposited by low-pressure plasma spraying and reacted with the Tl base material at a temperature above the eutectic temperature, the through-holes that are surface defects are melted and sealed in a vacuum, and a molten film is formed. This is to make it easier to solve this problem.

Furthermore, from the point of view of actual operation, the spraying current is 1200Amp,
Above plasma gas, Ar 80R/IIlin,
He 10, Q /win or more, reduced pressure atmosphere 10 Tor
The above element was identified because it is a metal that can easily melt surface defects and is easy to repair under conditions of r or less.

In the present invention, the powder is molded by cold isostatic pressing at 4,000 kg f/c or more, preferably 5,000 kg f/d, and 151 Ilin or more, and the surface of the titanium alloy sintered body obtained by sintering the powder compact is penetrated. Although it is covered with pores, the effect of metal adhesion on sealing the pores is industrially significant.

In other words, if hot isostatic pressing is performed in the two-phase temperature range of α and β of the mixed alloy component at 1000 kgf/c or more and 15 min or more, the number of through holes in the surface layer will decrease, and the remaining bores inside the part will be reduced. This eliminates the problem and produces high-density titanium alloy powder sintered products.

In this way, Cu, Ni, and C are deposited on the surface of the titanium alloy sintered body.
By depositing one of the elements O, Fe, and Mn by low-pressure plasma spraying, it is easy to seal the surface of a sintered body with a complex shape, and as a result of sealing the pores on the surface and inside of the sintered body, By increasing the density and refining the metal structure, we have made it possible to develop highly reliable products with excellent fatigue properties.

Examples of the present invention will be described below.

(Example 1) Two types of powder were prepared: a titanium powder consisting of 99.6% titanium, 0.09% oxygen, and 0.0005% or less of chlorine, and a master alloy powder having a composition of 60% aluminum and 40% vanadium.

Ti-6%Aρ-4%V titanium alloy specimen shape bar 10+++e'X 200mm' according to the following process
(length) was manufactured and its characteristics were investigated.

First step: Titanium and master alloy powders were mechanically mixed at a weight ratio of 9:1.

Second step: The mixed powder obtained in the first step was filled into an elastic rubber mold having a predetermined shape.

A rubber mold for a CIP test piece was prepared so that the product would be a fatigue test piece of 10+am' after HIP.

3rd step: 4000 kg of powder filled into a rubber mold
/C1 cold isostatic pressing for 15 minutes.

4th step: The green compact is vacuumed at 10-4 Torr, 125
Sintering treatment was performed at 0°C for 2 hours.

Fifth step: Insert the sintered body into a reduced pressure plasma spraying device,
The spraying current was 1400Amp. , the plasma gas is Ar
Under the conditions of 120 N/min, He 20 g/min s and a reduced pressure atmosphere of 20 Torr, the metal elements shown in Table 1 were deposited by vacuum plasma spraying for 5 minutes to form a molten film of about 10-. For comparison, a conventional method without this step was included.

6th step: Insert the sintered body subjected to low pressure plasma spraying into a hot isostatic press furnace and press at 900°C for 3 hours, 1000 kg
Hot isostatically pressed at f/c-.

Table 1 shows a comparison of metal elements, low pressure plasma spraying test results, and conventional methods.

The surface sealing state of each metal was observed together with the observation of the metal structure of the cross section of the sample. The density was determined by the Archimedes method, and the relative density was calculated in advance using a standard sample with no surface through-holes or internal bores remaining and is shown in Table 1. The fatigue strength test conditions in the table are axial force, stress ratio R-1, frequency f
- 2011z, in the atmosphere, at room temperature.

As is clear from Table 1, Cu, Ni, Co, Fe
, Mn, as a result of complete pore sealing treatment, there are no remaining bores inside the parts compared to conventional methods, and a powder sintered product of high-density titanium alloy is produced, reducing fatigue. It can be seen that the strength (number of 107 cycles) is also improved.

Table 1 (Example 2) Four types of powder: titanium powder consisting of 99.6% titanium, 0.09% oxygen, and 0.0005% or less of chlorine; mother alloy powder having a composition of 60% aluminum and 40% vanadium; A master alloy powder of 85% vanadium and 15% aluminum and a powder of 100% iron were prepared.

T I-10%V-2%Fe- according to the following steps
3%, l titanium alloy specimen shape 10mm'X2
00 mm' was manufactured and its characteristics were investigated.

1st King: Titanium, mother alloy 8Ω60V40+V85A
N15, iron powder weight ratio 85:2.5:1
Mechanical mixing was performed at a mixing ratio of 0.5:2.

Second step: The mixed powder obtained in the first step was filled into an elastic rubber mold having a predetermined shape.

A rubber mold for a CIP test piece was prepared so that the product would be a 10 mm' fatigue test piece after HIP.

Third step. 4,500 kg of powder filled into a rubber mold
Cold isostatic pressing was carried out at 15n+in at /C1.

4th step: The green compact is vacuumed at 10-'Torr, 130
Sintering treatment was performed at 0°C for 4 hours.

Fifth step: Insert the sintered body into a reduced pressure plasma spraying device,
The spraying current was +400Amp. , plasma gas is Ar 1
20 i) /win, He 20jil /mi
In a vacuum atmosphere of 20 Torr, the metal elements shown in Table 2 were deposited by vacuum plasma spraying for 5 minutes to form a molten film of approximately ICJttfn. For comparison, a conventional method without this step was included.

6th step: Insert the sintered body subjected to low pressure plasma spraying into a hot isostatic press furnace, press at 760°C for 3 hours, and press 1000 kg.
Hot isostatic pressing was carried out at f/c.

Table 2 shows a comparison of metal elements, low pressure plasma spraying test results, and conventional methods.

The surface sealing state of each metal was observed together with the observation of the metal structure of the cross section of the sample. The density was determined by the Archimedes method, and the relative density was calculated in advance using a standard sample with no surface through-holes or internal bores, and is shown in Table 2. Fatigue test conditions are axial force, stress ratio R-1, frequency f-2011z
, in air and at room temperature.

As is clear from Table 2, as a result of complete pore sealing in both Cu and Ni cases, the remaining bores inside the parts were eliminated compared to the conventional method, and high-density titanium alloys were It can be seen that a powder sintered product of 100% was produced and the fatigue strength (107 cycles) was also improved.

Table 2 (Example 3) Two types of powder, 99.6% titanium, 0.09% oxygen, 0.09% chlorine. A titanium powder consisting of OO059o or less and a mother alloy powder having a composition of 60% aluminum and 40% vanadium were prepared.

Ti-6%AΩ-4%V titanium alloy automotive stove 25mm'
200 mm' was manufactured and its characteristics were investigated.

First step: Titanium and master alloy powders were mechanically mixed at a weight ratio of 9:1.

Second step: The mixed powder obtained in the first step was filled into an elastic rubber mold of a connecting rod having a predetermined shape.

3rd step: 4oookg of powder filled into a rubber mold
Cold isostatic pressing was carried out at /c4 for 15 minutes.

4th step: The green compact is vacuumed at 10-'Torr, 125
[Sintering treatment was performed at 1°C for 3 hours.

Fifth step: Insert the sintered body into a reduced pressure plasma spraying device,
The spraying current was 1400Amp. , plasma gas is Ar 1
20 (1/win, He 2(11?/ak)
In a vacuum atmosphere of 20 Torr, Ni was deposited by vacuum plasma spraying for 15 minutes to form a molten film of about 10 layers. For comparison, a conventional method without this step was included.

6th step: Insert the sintered body subjected to low pressure plasma spraying into a hot isostatic press furnace and press at 900°C for 3 hours at IO00kg
Hot isostatic pressing was carried out at f/cd.

When a physical fatigue test was conducted on a connecting rod for an automobile, the method of the present invention was found to have an approximately 25% improvement in fatigue strength compared to the conventional method.

(Effects of the Invention) As is clear from the above description, the present invention eliminates defects in surface through-holes, which are a problem in the manufacture of titanium alloy sintered parts using powder metallurgy, without grinding. A high-density titanium alloy powder sintered product with excellent properties can be obtained.

The effect remains the same even if the metal is attached as a powder slurry.

Claims (1)

[Claims] titanium powder and one or more metal powders,
A mold is filled with mixed powder mixed to have a predetermined alloy composition, cold isostatic press molding is performed, and the powder compact is sintered.Cu is applied to the surface of the titanium alloy sintered body.
, Ni, Co, Fe, and Mn are deposited by low-pressure plasma spraying, followed by hot isostatic pressing.