JPH0633221A - Ti cementation method of ti-al based alloy member - Google Patents

Abstract

PURPOSE:To provide a method for Ti cementation of a Ti-Al based alloy member by which surface can be hardened in a large area. CONSTITUTION:The base body consisting of Ti-Al alloy is covered with a treating powder for mixing activating powder and ceramic powder for preventing sintering into Ti powder and heated in an inert atmosphere to diffuse Ti, and as necessary, further heated at 700-1100 deg.C for 10-50 hours in an inert atmosphere. Ti-Al based alloy member is heat-treated in the treating powder to allow Ti to be diffused and infiltrated. Thus even a member having a large area to be treated or a compolicated shape can be treated, and the obtd. Ti-Al alloy member has excellent wear resistance. Further, by heat treatment, Ti can be diffused and infiltrated into a deep region and the diffusion depth having wear resistance is extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of Ti diffusion and infiltration treatment for a Ti-Al alloy member.

[0002]

2. Description of the Related Art In a Ti-Al binary system, an intermetallic compound TiAl is present in a composition range of 35 to 42 atomic% Al at room temperature, and the intermetallic compound has a specific gravity of about 3.
Light weight of 8 and yield strength of 400MP up to 1070K
Since it has excellent mechanical properties such as a or higher, it is expected to be put to practical use in engines, turbines, etc. as a lightweight heat resistant structural material.

However, although the intermetallic compound TiAl is light in weight and excellent in high temperature strength and creep strength, it has poor hardness due to its low hardness and is applied to sliding members which are required to have high wear resistance. In order to do so, it was necessary to carry out a surface hardening treatment.

For example, in the invention of a wear-resistant Ti-based member disclosed in Japanese Patent Laid-Open No. 2-47278, TiAl is substantially used.
In the surface layer of the part where the wear resistance of the base material consisting of is required,
By disposing an aluminum powder and irradiating it with laser light, a layer mainly composed of a TiAl ₃ layer having an Al concentration of 48% or more is formed, and wear resistance is improved.
In the invention of the wear-resistant titanium alloy member of JP-A-229884, the aluminum 28 is formed by using the plasma overlay method on the site where the wear resistance of the base material made of TiAl is required.
A wear resistant layer mainly made of Ti ₃ Al containing up to 31% is formed to obtain a member having excellent wear resistance.

In the invention of the sliding part made of a TiAl-based alloy disclosed in JP-A-3-75385, these TiAl
It is pointed out that the TiAl alloy member does not have sufficient wear resistance to be used as an engine valve, and the surface of the TiAl alloy member is subjected to a physical process such as vapor phase plating or gas nitriding to have a thickness of 2 to 10 μm. It is disclosed that the wear resistance is improved by coating with the titanium nitride layer.

[0006]

By the way, in the invention of the wear-resistant Ti-based member disclosed in Japanese Patent Laid-Open No. 2-47278, wear resistance is improved by arranging aluminum powder on the surface layer and irradiating with laser light. In addition, in the invention of the wear-resistant titanium alloy member disclosed in JP-A-3-229884, the wear-resistant layer is formed by using the plasma overlay method.

However, although such a method is suitable for a limited portion (small area portion) such as an engine valve face for an automobile, for example, the entire surface of a part having a complicated shape, or a large area portion. Is difficult to apply.

The present invention has been invented to solve the above-mentioned problems in surface hardening treatment of a Ti-Al alloy member, and to a sliding member which requires wear resistance of the Ti-Al alloy member. It is an object of the present invention to provide a treatment method capable of performing a surface hardening treatment on a large-area portion or a complex-shaped portion in the application.

[0009]

DISCLOSURE OF THE INVENTION The inventor of the present invention has mainly used Ti ₃ containing 28 to 31% of aluminum in a portion requiring wear resistance of a base material mainly composed of a Ti—Al intermetallic compound.
Considering that the wear resistance of the sliding member can be ensured by forming the wear resistant layer made of Al, the idea of diffusing and permeating Ti was conceived, and earnest studies were conducted on the Ti diffusion method of the Ti—Al alloy member. As a result, they have found that Ti can be diffused and permeated by bringing an appropriate amount of Ti powder and a mixed powder of a halide and a ceramic powder into contact with the surface of the base material and heating the mixture to complete the present invention.

The Ti diffusion and infiltration treatment method for a Ti-Al alloy member of the present invention comprises:
Mixing ratio of 10 to 60 wt% titanium powder and 10 wt%
The gist of the present invention is to cover the following halogen compound and the treated powder of which the remainder is ceramic powder, and heat in an inert atmosphere to diffuse Ti. Further, in the present invention, if necessary, a base material made of a Ti—Al-based alloy in which Ti is further diffused is taken out from the treated powder, and further in an inert atmosphere at 700 to 1100 ° C. for 10 to 50 hours. Heat treatment.

The Ti--Al based alloy of the present invention comprises Al33-
It consists of a Ti-Al alloy containing 38% by weight. Al33 ~
38% by weight is the composition range of the Ti-Al based intermetallic compound mainly composed of TiAl. Here, T mainly composed of TiAl
The i-Al-based intermetallic compound mainly includes a TiAl intermetallic compound, and also includes TiAl ₂ , TiAl ₃ , and Ti ₃ Al.
And the like include intermetallic compounds.

If the Al content is less than 33% by weight, the proportion of the TiAl intermetallic compound in the TiAl alloy is small, resulting in a low specific gravity.
The improvement in high temperature strength and creep strength is not sufficient,
If 1 exceeds 38% by weight, the TiAl ₃ intermetallic compound tends to crystallize and becomes brittle. Therefore, the Al content of the base material is 3
If it is out of the range of 3 to 38% by weight, the strength characteristics of the wear resistant titanium alloy member will be poor.

The treated powder is composed of a metal powder that tends to diffuse and permeate, an alumina for preventing sintering of the metal powder, a ceramic powder such as kaolin, and ammonium chloride or a halide that is activated and adsorbed to and dissociates from the metal powder. The diffusion permeation treatment is performed by a so-called powder filling method in which the treated powder is filled around the member to be treated. Processing temperature is 700-1100
It is preferable that the temperature is in the temperature range of ° C and the treatment time is 2 to 20 hours.

When the film thickness is insufficient by the above treatment, it is possible to take out the object to be treated from the powder after the above treatment and increase the diffusion depth (modified thickness) by heat treatment. The conditions at that time are 700 to 1100 in an inert atmosphere.
The temperature range is 10 to 50 hours.

[0015]

The Ti-Al alloy member is heat-treated in the treated powder to diffuse and infiltrate Ti. Therefore, even a member having a large treated area or a member having a complicated shape can be treated and wear resistance is improved. An excellent Ti-Al alloy member can be obtained. Further, if necessary, 10 at 700 to 1100 ° C.
By performing the heat treatment for 50 hours, Ti diffuses and penetrates to a deeper portion, and the diffusion depth having abrasion resistance is expanded.

That is, a Ti-Al intermetallic compound mainly composed of Ti-Al exerts sufficient high-temperature strength and creep resistance on the base material, and Ti is used on the part where the wear resistance of the base material is required. By permeation and diffusion, a wear resistant layer made of a TiAl-based intermetallic compound mainly composed of Ti ₃ Al is formed, and sufficient wear resistance is exhibited.

In the present invention, the thickness of the surface modified portion is 5 to 5.
The thickness is preferably 1000 μm. If the thickness of the Ti diffusion layer is less than 5 μm, the surface modification effect is not sufficient, and conversely 10
This is because if it exceeds 00 μm, it takes a long time for the treatment and the surface-modified layer may peel off.

The amount of the Ti powder mixed in the treated powder is set to 10 to 60% by weight because if the amount is less than 10%, the surface-modified layer having a sufficient thickness cannot be obtained. This is because sintering causes the diffusion of Ti to be impossible and the thickness of the surface modification layer is greatly reduced.

Further, the amount of the activator such as ammonium chloride or aluminum fluoride added is 10%.
The reason why the content is set below is that the diffusion and permeation amount of Ti is rather reduced when the addition amount exceeds 10%. The ceramic powder acts to prevent sintering of the Ti powder at the processing temperature. Therefore, it is preferable to use a ceramic powder that does not decompose or sinter itself at the treatment temperature, for example, a stable oxide, and more preferably Al ₂ O ₃ or ZrO ₂ .

The diffusion and infiltration treatment temperature of Ti is 700 to 110.
The reason why the temperature range is 0 ° C. and the treatment time is 2 to 20 hours is that if the treatment conditions are less than 700 ° C. and less than 2 hours, the diffusion rate is slow and a sufficient treatment thickness cannot be obtained.
This is because if the treatment temperature exceeds 1100 ° C., the structure may change due to the transformation of the Ti—Al base material, and even if the treatment time exceeds 20 hours, the diffused Ti content is saturated and does not increase further. is there.

The heat treatment time of the base material made of a Ti-Al type alloy in which Ti is diffused is 700 to 1100 ° C. for 10 to 5 hours.
The time is set to 0 hour because the temperature is the same as that of the diffusion infiltration treatment, and when the time exceeds 50 hours, the member is distorted and the surface roughness deteriorates. This is because the effect of is not obtained.

[0022]

EXAMPLES Examples of the present invention will be described to clarify the effects of the present invention. (Example 1) Sample No. As No. 1, a columnar Ti—Al alloy (Ti—34 wt% Al) with a diameter of 10 × 10 mm was placed in an alumina crucible, and the periphery thereof was covered with a diffusing agent powder having the following composition. In this state, it was set in a high temperature furnace in an argon atmosphere and kept at 950 ° C. for 10 hours.

(Diffusing agent-treated powder composition) Ti powder (80 to 200 mesh) 50% by weight Ammonium chloride powder (-275 mesh) 2% by weight Al ₂ O ₃ powder (80 to ₂₀₀ mesh) 48% by weight

Sample No. 2, the sample No. A cylindrical TiAl alloy (Ti-34 wt% Al) of φ10 × 10 mm that has been subjected to Ti diffusion and penetration treatment in the same manner as in 1 was taken out from the alumina crucible, the powder adhering to the periphery was removed, and the surface was washed with an organic cleaning agent such as trichloroethane. Washed with. This sample No. Place 2 in a furnace with an argon atmosphere and set 1
A heat treatment of holding at 100 ° C. for 20 hours was performed.

Sample No. obtained by the above treatment 1 and No. 2 was cut and the cross-sectional structure was observed. When the treatment layer thickness was measured, No. In No. 1, it was 10 μm. However, no. In No. 2, the interface between the film and the base material was not clear, and it was difficult to determine the film thickness due to the difference in structure.

Next, the treated layer was identified by X-ray diffraction. As a result, the base material and the treated layer No. 1, No.
The following compounds were detected for 2 respectively. Base material: Ti ₃ Al, TiAl (underline shows a strong peak) No. 1: Ti ₃ Al, TiAl (underline shows a strong peak) No. 2: Ti ₃ Al, TiAl (underline shows a strong peak) Here, the peak of Ti ₃ Al is strongly detected in the treated layer. TiAl alloy is TiAl and Ti ₃ Al
Sample No. 1 and No. It was estimated from the above results that the treatment ratio of No. 2 was such that the mixture ratio was rich in Ti ₃ Al.

In order to clarify the composition of the treatment layer, the EPM
The Al concentration distribution was investigated by A line analysis. The result is shown in FIG. As shown in FIG. 1, the sample No. subjected to only the diffusion and penetration treatment. In No. 1, the Al content changes rapidly at the interface of the treatment layer. Further, the Al content of the treated layer is 28
Since the content was wt%, it was estimated that most of the treated layer was composed of Ti ₃ Al.

On the other hand, sample N which was heat-treated after the diffusion treatment
o. In No. 2, it can be seen that the Al content changes continuously. This was presumed to be because Ti near the surface was diffused to the inside by the heat treatment, and as a result, the mixing ratio of Ti ₃ Al and TiAl was changed.

(Example 2) In order to investigate the effect of the Ti content of the diffusion-treated powder on the thickness of the treatment layer, the diffusion-treated powder in which the Ti content was mixed in the range of 5 to 100% by weight was used. In the same method and conditions as in No. 1, Ti-A
The Ti alloy was subjected to Ti diffusion treatment, and the thickness of the treated layer in which Ti was diffused was measured. The result is shown in FIG.

As shown in FIG. 2, when the Ti content in the treated powder is 10% by weight or less, the treated layer thickness is rapidly reduced. This is because the Ti powder, which is a diffusion raw material, was insufficient because the Ti powder was not in sufficient contact with the base material. On the other hand, when the content is 80% by weight or more, the treated powder was sintered and the treated powder was bonded to the base material, so that the sample could not be taken out. At 70% by weight, although the sample could be taken out, the thickness of the treated layer was drastically reduced. This is because a part of the treated powder was sintered, which made it impossible to supply Ti sufficiently. From the above results, it was confirmed that when the Ti content in the treated powder was treated at 10 to 60% by weight, Ti could be diffused and permeated with a desired treatment layer thickness.

Example 3 Using the same base material and treated powder as in Example 1, the treatment temperature and time were changed as shown in Table 1 to carry out diffusion treatment, and the treatment layer thickness was measured. The results are also shown in Table 1. In Table 1, N
o. No. 1 is a comparative example in which the diffusion treatment temperature is low, and No. 1 No. 5 is a comparative example having a short diffusion processing time. No. 9 is a comparative example in which the heat treatment temperature after the diffusion treatment is low, and No. 9 No. 13 is a comparative example in which the heat treatment time after the diffusion treatment is short, No. 13 Reference numeral 16 is a comparative example in which the heat treatment time after the diffusion treatment is long.

[0032]

[Table 1]

As shown in Table 1, No. No. 1 of the comparative example having a low diffusion treatment temperature and No. In Comparative Example 5 in which the diffusion treatment time was short, Ti did not diffuse sufficiently and the treatment layer thickness was 2 to 3 μm.
It was as thin as m. In addition, No. No. 9 in which the heat treatment temperature after the diffusion treatment is low and No. In Comparative Example 13 in which the heat treatment time after the diffusion treatment was short, the diffusion of Ti in the treatment layer was insufficient and the thickness of the treatment layer was 13 μm. On the other hand, Comparative Example No. 1 in which the heat treatment time after the diffusion treatment was as long as 70 hours. 16
, The base material was distorted and the surface roughness became large.

On the other hand, in the examples of the present invention, it was found that the desired treatment layer thickness was obtained, and the diffusion permeation treatment conditions were such that the treatment temperature was 700 to 1100 ° C. and the treatment time was 2 It was confirmed that the heat treatment is preferably -20 hours, and the heat treatment after the diffusion treatment needs to be 700-1100 ° C for 10-50 hours.

(Example 4) Sample No. 1 of Example 1 For No. 2, the hardness distribution of the cross section was measured, and the results are shown together in FIG. 3 as a relational diagram with the Al content. As is clear from FIG. 3, the hardness decreases as the Al content increases, that is, as it moves from the surface to the inside. This is due to the mixing ratio of Ti ₃ Al and TiAl, and the hardness of Ti ₃ Al is about 400H.
Since the hardness of v and TiAl is about 200 Hv,
I can explain.

(Example 5) Sample N prepared in Example 1
o. 1 and No. Abrasion test of two treated layers was performed.
As shown in FIG. 4, the wear test was performed on the treated layer of the sample with SS4.
The ring consisting of 1 was pressed under a load of 2 to 12 kg, rotated at a rotation speed of 200 rpm for 30 minutes, and the abrasion amount mm ³ of the treated layer was measured. The obtained results are shown in FIG. For comparison, untreated product and PVD-based T
The iN-coated product (film thickness: 5 μm) was similarly subjected to the abrasion test, and the results are also shown in FIG.

Sample No. which is the product of the present invention. 1 and No.
Both of them exhibited excellent wear resistance at low load as compared with the untreated product. On the other hand, in the high load range, the sample No. Although the wear amount of Sample No. 1 increased slightly, Sample No. 1 and No.
Both are untreated under low load and TiN by PVD
It showed superior wear resistance compared to the coated product. As a result, the effect of the present invention was confirmed, and No. The reason why the wear amount of No. 1 was slightly high under high load is that the film thickness is N
o. 1 is due to the thinness of 10 μm,
When using in such a high load range, No. It has been found that it is preferable to perform the treatment of enlarging the treatment layer by heat treatment such as 2.

(Embodiment 6) In order to evaluate the actual equipment of the present invention, a TiAl alloy (Ti-34 wt% Al) was used.
A piston pin for an automobile engine was manufactured and No. 1 was produced under the same conditions as those shown in Example 1. No. 1 was subjected to Ti diffusion and infiltration treatment, and No. 1 was used. Regarding No. 2, after the Ti diffusion and infiltration treatment, further heat treatment was performed. Also, for comparison, similar piston pins were prepared for the untreated product and the PVD TiN-coated product.

These piston pins were incorporated into a 3l-8 cylinder engine and the actual machine was evaluated. The evaluation conditions are: 4000 rpm full load operation 6 with over-absorption pressure of 650 mmHg.
Minutes → [Idle operation 1 minute] → [Stop 6 minutes] → [Idle operation 1 minute] was set as one cycle, and this cycle was repeated to evaluate whether there was wear or abnormality. The results obtained are summarized in Table 2.

[0040]

[Table 2]

As shown in Table 2, the untreated product was worn out in 100 hours and stopped in 150 hours. Also PVD
The (TiN coated) product started to wear at 150 hours and could only be operated for up to 250 hours. On the other hand, the product of the present invention exhibited excellent performance and was the performance of clearing the target value of 500 hours, and the effect of the present invention was confirmed.

[0042]

EFFECTS OF THE INVENTION Ti applied to the Ti--Al alloy member of the present invention
As described in detail above, the diffusion permeation treatment method is performed by covering a base material made of a Ti-Al alloy with a treated powder in which titanium powder is mixed with an activator powder and a stable oxide for sintering prevention, and an inert atmosphere is used. Heating in an atmosphere to diffuse Ti and, if necessary, further in an inert atmosphere at 700 to 1100 ° C. for 10 to 10
The heat treatment is performed for 50 hours, and the Ti-Al alloy member is heat treated in the treated powder to obtain T
Since i is diffused and permeated, even for members with a large processing area,
Further, even a member having a complicated shape can be processed, and a Ti-Al alloy member excellent in wear resistance can be obtained. Further, by heat treatment, Ti diffuses and penetrates to a deeper portion. The diffusion depth with wear resistance is expanded.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the distance from the surface of a treated layer treated by the method of the present invention and Al content.

FIG. 2 is a diagram showing the relationship between the Ti content in the treated powder and the treated layer thickness.

FIG. 3 is a diagram showing a relationship between Al content and hardness of a treated layer treated by the method of the present invention.

FIG. 4 is a perspective view illustrating a test method of a wear test.

FIG. 5 is a diagram showing a relationship between a load and a wear amount in a wear test.

Claims (2)

[Claims] 1. A base material made of a Ti--Al alloy is covered with a treated powder having a mixing ratio of 10 to 60 wt% titanium powder, 10 wt% or less of a halogen compound, and the balance being ceramic powder, and an inert atmosphere. Ti in a Ti-Al based alloy member characterized by heating in an atmosphere to diffuse Ti
Diffusion and penetration treatment method. 2. A base material made of a Ti—Al-based alloy in which Ti is diffused is taken out from the treated powder, and further heat-treated at 700 to 1100 ° C. for 10 to 50 hours in an inert atmosphere. Ti- according to claim 1, characterized in that
A method for diffusing and permeating Ti into an Al-based alloy member.