JP3077867B2 - Method of oxidizing TiAl intermetallic compound for sliding member with excellent wear resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding part having excellent wear resistance.
The present invention relates to a method for oxidizing TiAl intermetallic compounds for materials .

[0002]

2. Description of the Related Art In a Ti-Al binary system equilibrium phase diagram,
In the composition range of 35 to 42% by weight Al at room temperature,
Since the intermetallic compound TiAl is present and has a specific gravity of about 3.8, which is lightweight and has excellent mechanical properties such as a proof stress up to 1070K of 400 MPa or more, it is used as a lightweight heat-resistant structural material for an engine. It is expected to be applied to turbines and turbines.

[0003] The TiAl intermetallic compound, as well as other intermetallic compounds brittle than ordinary metals and alloys, poor room temperature ductility, the TiAl + Ti ₃ Al phase boundary prone Ti near the relatively ductile Investigations have been continued mainly on compounds having a similar composition. Therefore, as a practical composition of a Ti—Al-based alloy, a stoichiometric composition of 36% by weight of Al
Further, a third element such as Mn, V, Si, Nb, Cr, or Mo is added to a Ti-rich compound to improve ductility or oxidation resistance.

[0004] When these Ti-Al-based alloy members are used as valve train members such as engine valves and valve stems, there arises a problem of wear resistance. JP Hei 3
In the invention of the parts for sliding parts made of TiAl-based alloy disclosed in Japanese Patent No. 75385/75, it is pointed out that these Ti-Al-based alloys do not have sufficient wear resistance to be used as an engine valve, It is disclosed that the wear resistance is improved by coating the surface of the member with a titanium nitride layer having a thickness of 2 to 10 μm by a process such as vapor phase plating or gas nitriding by a physical process.

[0005] In addition, as an invention for forming an oxide film on a Ti-Al-based member, there is an invention disclosed in Japanese Patent Application Laid-Open No. 2-294458. In this invention, only Al is used without oxidizing Ti under a low oxygen partial pressure. Is selectively oxidized to form an Al ₂ O ₃ coating to improve the oxidizing property of the Ti-Al-based alloy member, and is not intended to improve wear resistance. The relationship with the abrasion resistance has not been reported and was unknown.

[0006]

On the other hand, TiN and Ti ₂ AlN produced by nitriding of the TiAl intermetallic compound are unstable in a high temperature environment (for example, at a temperature of 700 ° C. or higher) and decompose. It is said that it is easy to do. In contrast, TiAl oxide is said to be stable even at high temperatures. In view of the above, an object of the present invention is to provide a method for oxidizing a TiAl intermetallic compound for a sliding member, in which an oxidizing method for a TiAl intermetallic compound is repeatedly studied, and an oxidized film having excellent wear resistance is obtained. I do.

[0007]

Means for Solving the Problems The inventors of the present invention have studied the conditions of the oxidation treatment, that is, the relation between the processing temperature, the processing time, the processing pressure, the Al content of the processing material, and the wear resistance of the material to be processed.
We continued our research. As a result, they have found that there is a certain relationship between these factors and wear resistance, and have completed the present invention.

[0008] The sliding excellent in wear resistance according to claim 1 of the present invention.
Oxidation method members for TiAl intermetallic compound, abrasion
This is a method of oxidizing a TiAl intermetallic compound for a sliding member having excellent properties, and in an atmosphere containing at least oxygen, T + 50 logH ≧ 750 (a) 500 + 25 × Al ≧ T (.) (B) [where, T: processing temperature (° C.), H: processing time (h),
Al: Al (% by weight of the material to be treated)] is to be heated and oxidized.

The sliding with excellent wear resistance according to claim 2 of the present invention.
The method for oxidizing a TiAl intermetallic compound for a member is the method for oxidizing a TiAl intermetallic compound for a sliding member excellent in wear resistance according to claim 1, wherein 25logH + T + 0.4P <1150 (c) , P: pressure (Torr)], and perform oxidation treatment.

[0010] The titanium-based alloy that is the object of the present invention is Ti
_The center is an intermetallic compound containing both 3Al (α ₂ phase) and TiAl (γ phase). Mn, Cr, Mo, TiAl
It is also effective for a material to which Si or the like is added as a third element.
The Al content of TiAl is 30 to 37% by weight. Other compositions are not suitable for practical use due to low ductility.

It is desirable that the surface of the TiAl material to be treated according to the present invention be degreased and cleaned prior to the oxidation treatment. Degreasing and cleaning of the TiAl member can be performed by a conventionally known method. For example, in the case of degreasing, alkali degreasing, electrolytic degreasing, solvent degreasing, and the like can be used. In addition, if moisture and organic solvents remain after cleaning, they will react with the TiAl base material at a high temperature. Therefore, after applying residual heat in a vacuum to remove these components from the surface, the temperature is raised to a predetermined temperature. It is desirable.

The atmosphere for the oxidation treatment contains at least oxygen, for example, by introducing oxygen or atmospheric gas.

[0013]

According to the first aspect of the present invention, the lower limit of the treatment time (H) and the temperature (T) among the oxidation treatment conditions of the TiAl intermetallic compound for a sliding member having excellent wear resistance is set to ( a) Since T + 50 logH ≧ 750 (a), a good oxide layer is formed, the surface roughness is smooth, and an oxide film excellent in wear resistance can be obtained.

[0014] Also, TiA for sliding members excellent in wear resistance.
l Among the oxidation treatment conditions for intermetallic compounds, treatment time (H)
And the upper limit of the temperature (T) is expressed by the equation (b), 500 + 25 × Al ≧ T (b), so that the structure does not change and the material strength does not decrease.

According to the first aspect of the present invention, the abrasion resistance is excellent.
The lower limit of the processing time (H) and the temperature (T) in the oxidation treatment conditions of the TiAl intermetallic compound for a sliding member is set to the expression (a) because the temperature and the processing time do not satisfy the expression (a). This is because a good oxide layer is not formed, and the surface roughness becomes rough, so that an oxide film having excellent wear resistance cannot be obtained.

Also, TiA for sliding members having excellent wear resistance.
l Among the oxidation treatment conditions for intermetallic compounds, treatment time (H)
The reason why the upper limit of the temperature (T) is set to the expression (b) is that if the temperature and the processing time do not satisfy the expression (a), the structure changes and the material strength decreases.

(Claim 2) In the invention of claim 2, the pressure (P), the treatment time (H) and the temperature (T) of the oxidation treatment conditions of the TiAl intermetallic compound for a sliding member having excellent wear resistance. ) Is set to the following expression (c): 25 logH + T + 0.4P <1150 (c), so that generation of scale and surface roughening are suppressed.
Good wear resistance can be ensured.

According to the second aspect of the present invention, the abrasion resistance is excellent.
The upper limit of the pressure (P), the processing time (H) and the temperature (T) in the oxidation treatment conditions of the TiAl intermetallic compound for a sliding member is defined by the expression (c). In such a case, the oxide generated on the surface deteriorates the surface roughness, and the surface may be covered with scale in some cases. Then, by further adding the condition of the expression (c), the generation of scale and the roughening of the surface can be suppressed, and good wear resistance can be secured.

[0019]

EXAMPLES Examples of the present invention will be described in comparison with comparative examples,
The effect of the present invention will be clarified. (Example 1) 31% by weight and 34% by weight of Al content
After the sample made of TiAl alloy was degreased and washed, it was placed in a vacuum heating furnace to be evacuated to 1 × 10 ⁻³ Torr. next,
Heating was performed to each temperature shown in Table 1, oxygen gas at a pressure of 760 Torr was introduced into a vacuum heating furnace, and nitriding treatment was performed for 2 hours. After the nitriding treatment, the tensile strength of each sample was measured, and the results are shown in Table 1. Note that (500 + 25 × Al weight%) ° C. is 1275 ° C. for 31 Al weight% and 135 for 34 Al weight%.
0 ° C.

[0020]

[Table 1]

As is evident from Table 1, the treatment temperature is (5
In Comparative Examples 1 and 2, which exceeded the upper limit temperature of (00 + 25 x Al wt%) ° C, the tensile strength was 14.
It was remarkably reduced to ⁴ to 15.7 kgf / mm ² . In contrast, Examples 1 and 2 of the present invention, in which the processing temperature was lower than the upper limit temperature of (500 + 25 × Al wt%) ° C., were found to maintain the original tensile strength, and the effect of the present invention was confirmed. Was done.

Example 2 Ti having an Al content of 34.5%
After preparing a test piece made of Al alloy, degreased and washed,
It was placed in a vacuum heating furnace and kept in a vacuum of 1 × 10 ⁻³ Torr. Then, 760 Torr and 1 × 10 ⁻⁴ Torr
, And oxidized at the respective temperatures shown in FIGS. 1 and 2 for the respective processing times shown in FIGS. 1 and 2.

After nitriding the test pieces, LFW
A wear test was performed. In this wear test, as shown in FIG. 3, a cylindrical test piece made of cast iron (JISFC20) having an outer diameter of 35 mm, an inner diameter of 30 mm, and a width of 10 mm was used as a mating material, and the test piece was brought into contact with the room temperature lubricating oil. In addition, a wear test is performed for 30 minutes at a rotation speed of 5 rpm and a pressing force of 60 kgf against a partner material. The result obtained is that the wear amount is 10
Those exceeding 0 μm are marked with “x” and the wear amount is 10 to 100 μm
Are marked with a triangle, and those with a wear amount of 10 mm or less are marked with a circle, as shown in FIG. 1 and FIG. Note that the lines shown in FIG. 1 and FIG. 2 are both lines representing the expression (a).

As is apparent from FIGS. 1 and 2,
(A) All the test pieces having the oxidation treatment time (H) and the oxidation treatment temperature (T) equal to or larger than the expression (a) are marked with a circle and have a wear amount of 10 or more.
It was confirmed that an oxidized film excellent in abrasion resistance was formed under the oxidizing condition satisfying the expression (a) below μm.

Example 3 Ti having an Al content of 34.5%
After preparing a test piece made of Al alloy, degreased and washed,
It was placed in a vacuum heating furnace and kept in a vacuum of 1 × 10 ⁻³ Torr. Then, 760 Torr and 1 × 10 ⁻⁴ Torr
, And at the respective temperatures shown in FIGS. 4, 5 and 6, FIG.
The oxidation treatment was performed for each treatment time shown in FIG. 5 and FIG.
In addition, the treatment time was fixed at 1 hour, and the oxidation treatment at each pressure and treatment time shown in FIG. 6 was performed.

These test pieces were subjected to the same LFW abrasion test as in Example 2 after the oxidation treatment. The results obtained are indicated by a mark x when the wear amount exceeds 100 μm, and when the wear amount is 10 to 10 μm.
Those having a thickness of 100 μm are indicated by Δ, and those having a wear amount of 10 mm or less are indicated by O in FIGS. 1 and 2. Note that the lines shown in FIG. 4 and FIG. 5 are lines expressing the expression (c).

As is clear from FIGS. 4, 5 and 6, all the test pieces having the oxidizing treatment pressure (P), oxidizing treatment time (H) and oxidizing treatment temperature (T) below the equation (c) are ○.
The mark indicates that the abrasion amount was 10 μm or less, and it was confirmed that an oxidation treatment film having excellent wear resistance was formed under the oxidation treatment conditions satisfying the expression (C).

[0028]

According to the first aspect of the present invention, the slide having excellent wear resistance.
As described in detail above, the method of oxidizing the TiAl intermetallic compound for a moving member is carried out in an atmosphere containing at least oxygen under T +
50 logH ≧ 750 (a) Expression and 500
+ 25 × Al ≧ T Expression (b) [where T:
3. Abrasion resistance according to claim 2, characterized in that the oxidizing treatment is carried out by heating under a condition of a treatment temperature (° C.), H: treatment time (h), Al: Al (% by weight) of the material to be treated . Excellent
The method for oxidizing a TiAl intermetallic compound for a sliding member according to claim 1 is the method for oxidizing a TiAl intermetallic compound for a sliding member having excellent wear resistance , wherein T + 25logH + 51.
5logP <994: A slide characterized by being heated and oxidized under the condition of formula (c) [where P: pressure (Torr)], and having excellent wear resistance. Department
An oxide film having excellent wear resistance can be obtained on the surface of the TiAl intermetallic compound for a material .

[Brief description of the drawings]

FIG. 1 is a diagram showing a wear amount of a test piece oxidized at various treatment times and treatment temperatures at a pressure of 760 Torr and a straight line showing the formula (a).

FIG. 2 is a diagram showing a wear amount of a test piece oxidized at various processing times and temperatures at a pressure of 1 × 10 ⁻⁴ TorrTorr and a straight line indicating the equation (a).

FIG. 3 is a side view of a wear-resistant test piece and a mating material.

FIG. 4 is a diagram showing a wear amount of a test piece oxidized at various treatment times and treatment temperatures at a pressure of 760 Torr and a straight line showing the equation (c).

FIG. 5 is a diagram showing a wear amount of a test piece oxidized at various processing times and temperatures at a pressure of 1 × 10 ⁻⁴ Torr and a straight line indicating the equation (c).

FIG. 6 is a diagram showing a wear amount of a test piece oxidized at various processing pressures and temperatures at a processing time T = 1 hour and a straight line indicating the equation (c).

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 8 / 12,14 / 00

Claims (2)

(57) [Claims] 1. A method for oxidizing a TiAl intermetallic compound for a sliding member having excellent wear resistance , wherein T + 50logH ≧ 750 (a) 500 + 25 × Al ≧ in an atmosphere containing at least oxygen. T ... (b) [where T: treatment temperature (° C.), H: treatment time (h),
Al: The material to be treated is Al (% by weight)], and is heated and oxidized to provide excellent wear resistance.
A method for oxidizing a TiAl intermetallic compound for a sliding member . 2. The method for oxidizing a TiAl intermetallic compound for a sliding member having excellent wear resistance according to claim 1, wherein: 25 logH + T + 0.4P <1150 (c) ), H: processing time (h),
P: a T for a sliding member having excellent wear resistance , which is heated and oxidized under a condition of pressure (Torr)].
Oxidation treatment method of iAl intermetallic compound.