JPH01201489A - Production of sliding member made of al alloy - Google Patents

Abstract

PURPOSE:To produce a sliding member made of an Al alloy having excellent seizure resistance and wear resistance by alloying the hydride of a metal on the surface layer of an Al alloy base material by using high-density energy, thereby crystallizing an intermetallic compd. and forming pores. CONSTITUTION:Powder 2 of the hydride of the metal such as Ti or Zr which can form the intermediate compd. with Al is coated and disposed on the surface of the base material consisting of the Al alloy. An arc 4 is then applied onto this powder fixed layer 2 from above by using a TIG torch 3 to melt the powder fixed layer 2 and the surface layer of the Al alloy base material 1 on the lower side thereof. The alloyed layer is thereby formed on the surface layer of the base material. The high-hardness intermetallic compd. is crystallized into the surface layer by this alloying treatment; in addition, the pores which function as oil pools are formed to 2-30% porosity by the gaseous hydrogen which is generated by decomposition of the metal hydride.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to sliding members made of aluminum alloy that have a portion that slides on a mating member, such as pistons and cylinder liners for internal combustion engines, pulp lifters, shift forks, etc. The present invention relates to a manufacturing method, and in particular to a method of manufacturing a sliding member having a porous modified surface layer.

Traditional technology! Internal combustion intercondylar pistons used in lj cars include:
Aluminum alloys are generally used because they are required to be lightweight, but pistons and other materials are required to have good wear resistance because they are members that slide against the mating material. It is being Therefore, for sliding members such as pistons made of aluminum alloy, hypereutectic Affi-
8i alloy is being used. However, since the normal hypereutectic Al-8i alloy has slightly inferior strength and toughness, there is a problem in forming the entire sliding member from the hypereutectic Ae-3i alloy.

By the way, aluminum alloys produced by powder metallurgy, which have high strength, high toughness, and high heat resistance, are also used for sliding parts. It is usual to apply hot heat treatment to make a sliding member.

However, the wear resistance of the hypereutectic Al-3i alloy sliding member produced by this method is poor because the grain size of the primary 3i crystals is generally less than 10 mm, compared to the tens of tens of degrees in the case of cast materials. Moreover, since the structure is dense and there are few pores that act as oil reservoirs on the surface, there is also the problem that seizure is likely to occur.

Therefore, in JP-A No. 62-112705, a rough shape is formed from hypereutectic AN-3i alloy powder, the rough shape is partially degassed as necessary, and then heated. A sliding member with a predetermined shape is obtained by machining, and then the sliding surface is irradiated with high-density energy such as a laser to remelt the surface layer, and the diameter of the primary crystal 3i is relatively large by cooling and solidifying it. A method has been proposed for forming a surface modified layer (remelting layer) having a diameter (25 to ioog) and a porosity of 2 to 30%. The surface-modified layer of the sliding member obtained by this method has pores in which relatively large diameter primary crystals S1, which are effective against sliding wear, are dispersed and can act effectively as an oil reservoir. Because of this, it has excellent wear resistance and is less likely to seize.

Problems to be Solved by the Invention In the case of the method of JP-A-62-112705 mentioned above, Al
Rough shapes are formed from alloy powder, degassed if necessary, hot worked, and then remelted i! ! There is a problem in that it requires complicated processing steps, and in particular, it requires a great deal of time and cost to form a rough shape from powder. In addition, in this method, alloy components with excellent wear resistance are used throughout the sliding member, which is not only wasteful in terms of cost, but also reduces the degree of freedom in selecting the component composition of the base material. In some cases, the properties required for the base material portion could not be fully satisfied.

This light beam was created against the background of the above circumstances, and it is possible to obtain an Al alloy sliding member with excellent surface seizure resistance and wear resistance at a low cost, and also has excellent wear resistance and seizure resistance. To provide a method for manufacturing a sliding member made of He2 alloy, which not only reduces costs but also provides a greater degree of freedom in selecting the composition of the base material by forming a layer with excellent properties only on the surface. This is the purpose.

Means for Solving the Problems This method of manufacturing a sliding member made of an optical Al alloy includes adding a metal hydride that can form an intermetallic compound with Al to the surface layer of a base material made of a He2 alloy. Alloying is performed using high-density energy, thereby crystallizing intermetallic compounds in the surface layer, and increasing the porosity between the surface and the inside by 2 to 30% due to hydrogen gas photogeneration accompanying the decomposition of the metal hydride. It is characterized by this.

Action A metal hydride that can form an intermetallic compound with AN,
When alloyed with the surface layer of the He1 alloy substrate using high-density energy, the metal hydride and A! The metal hydride is melted and integrated with the surface layer of the alloy base material to form an alloy. At this time, the metal hydride decomposes into a metal component and hydrogen gas. Among them, the metal component combines with the 8β of the base material to generate an intermetallic compound, and the hydrogen gas becomes bubbles in the molten R layer to generate a large number of pores. Therefore, the surface layer (modified layer) after the alloying treatment has a structure in which the intermetallic compound of Al and the curved metal is crystallized and in which a large number of pores are present.

Eight here! Intermetallic compounds with other metals are generally harder than the matrix α-Al phase, so they play the role of supporting the load during sliding with the mating material, ensuring wear resistance, and at the same time reducing porosity. When exposed on the surface, it functions as an oil reservoir to ensure seizure resistance. Therefore, the surface modified layer subjected to the above-described treatment has excellent wear resistance and seizure resistance.

If the ratio of pores (porosity) in the surface modified layer produced by the alloying treatment of metal hydrides as described above is less than 2%, the effect of oil accumulation due to pores is almost eliminated, and sufficient seizure resistance is achieved. is not obtained. On the other hand, if the porosity exceeds 30%, the strength will be insufficient and damage may occur. Therefore, the porosity needs to be within the range of 2 to 30%.

The porosity in the surface modified layer can be determined by changing the hydrogen content in the metal hydride used for alloying and the alloying ratio (the ratio of the melted part of the base material surface to the alloying material). Adjustment can be covered. In addition, the hardness of the surface modified layer can be adjusted by changing the type of metal component of the metal hydride to be alloyed and the alloying ratio, and thus the degree of wear resistance to be improved over that of the base material can be adjusted. Can be done.

In addition, alloying 51 as described above! It is only the surface layer of the Al alloy base material that is given the wear resistance and seizure resistance that has been obtained through processing, and the base 1 part excluding that surface layer is the same as the original A.
The composition of the two alloy base materials remains the same. In short, the A2 alloy base material only needs to be an A2 alloy mainly composed of Al, and can have any composition, so there is a large degree of freedom in composition of the base material.

Specific explanation for implementation of defense In implementing the method of this invention, 1. 2. Parts of the alloy base material that slide against the mating material, that is, wear resistance
Metal hydride powder as described above is placed in advance on the surface of the part to which seizure resistance is to be imparted, and high-density energy such as a laser, TIG arc, plasma arc, or electron beam is applied from above. The metal hydride powder and the surface layer of the base material below it may be melted simultaneously. The metal hydride powder can be placed on the substrate by placing it directly, by applying it as a slurry, or by hardening it onto the substrate using a suitable binder. Also good. In some cases, high-density energy may be applied while supplying metal hydride powder onto the base material.

The metal component constituting the metal hydride may be any metal as long as it can form a hard intermetallic compound with Al, and for example, M(], 7i, Nb, v, Zr, etc. can be used. Here, when a hydride of Mg is alloyed, M(J2Al3 is crystallized as an intermetallic compound, when a hydride of Ti is used, TiAf3 is formed, and when a hydride of zr is used, ZrAJ'3 is formed. Of these intermetallic compounds, TlAl3 and zrAi!3 are harder than M92A&3, so in order to sufficiently increase the hardness of the surface modified layer and sufficiently improve wear resistance. for,
It is desirable to use Ti hydride or Zr hydride.

Also, the metal hydride itself contains hydrogen! (J is usually Mizuki solid solution suspension) can be adjusted, and if a metal hydride with a high hydrogen content is used, the porosity will increase, but the amount of crystallization of intermetallic compounds will decrease (however, the alloying rate remains the same) However, if a metal hydride with a low hydrogen content is used, the amount of intermetallic compounds crystallized increases, but the porosity tends to decrease).

Therefore, the resistance of the A2 alloy base material to 1? When the wear resistance is relatively good, the seizure resistance is mainly improved by increasing the porosity using a metal hydride with a high hydrogen content, and conversely, when the wear resistance of the Al alloy base material itself is low. It is desirable to mainly improve wear resistance by increasing the amount of metal rJ compound produced by using a metal hydride with a low hydrogen content.

Example [Example 11 As shown in Fig. 1, 0.3 g of titanium hydride powder with hydrogen solid solution of 15 cc/100 g was added to the area of 10×3011 #I on the surface of the Al alloy base material 1 made of JIS A02B.
An unmixed layer 2 was formed by adding the same amount of polyvinyl alcohol as a binder. Next, an arc 4 is applied from above the powder layer 2 using a TIG torch 3 to simultaneously melt the powder layer 2 and the surface layer of the alloy layer 1 below it. A chemical treatment was carried out to form an alloyed layer (surface modified layer) 5 as shown in FIG. This Togi no T
IG 7-The markings ft are as follows.

Output Peak current 150A Base current 120A (application time of peak current and base current is 0.5 seconds each) Torch feed speed: 1.5am/S Shield gas flow Φ: 155/l1tI Electrode diameter: 448 dark φ electrode - trial Distance between pieces: 2. When the structure of the alloyed layer (surface modified layer) formed in this way was investigated, it was found that the area ratio of Ai'3T i was about 30%.
It was found that intermetallic compounds (hardness Hv 710) were crystallized and the porosity was about 8%.

[Example 21 Alloyed layer J! by 1' IG arc was prepared in the same manner as in Example 1 except that titanium hydride powder having a hydrogen solid solution amount of Icc/100 g was used. was carried out to form an alloyed layer (surface modified layer).

When the structure of this alloyed layer was examined, it was found that the amount of Ai'3Ti intermetallic compound crystallized was about 30% as in Example 1, and the porosity was about 3%.

[Performance evaluation test] The surface of the Al alloy base material (
An alloyed layer was formed in an annular region with a width of 7111 #I (inner edge radius: 8 mm, outer edge radius: 15 mm) on the flat surface), and the surface was finished. 30 tnr each from these samples.
A test piece having a size of t x 30 HH x 5 rI #l was cut out and subjected to a seizure limit test using a mechanical testing laboratory type friction and wear tester. At this time, the mating test piece was 5C.
Cylindrical test piece made of r420 (JIS G4104) carburized and quenched (inner diameter 20rR11L souter diameter 25.6m)
s, length 16a#I), and the test conditions were set as follows.

Slip speed: 2.4 m/sec Al Lubricating oil: Low viscosity oil Temperature: 60°C In this seizure limit test, the surface pressure was increased to 12.5 Aig every 2 minutes.
/C- each B large 250 up to 9/cji? 8, the minimum n1 (seizing surface pressure) at which seizure occurs was investigated.

In this case, both the alloyed layer formed in section f) of Example 1 and the alloyed layer formed in section 1'1 of Example 2 have a baking surface pressure of 250 Kfl/'cti or less. It dawned on me.

For comparison, the same seizing limit test was conducted on untreated material (without alloyed layer), but in this case, the seizing surface pressure was 150 kg/'ci, so the material formed according to Examples 1 and 2 It is clear that the alloyed layer has significantly improved seizure resistance.

The sliding member obtained by the method of the present invention has excellent seizure resistance as the pores in the surface layer modified by the alloying treatment function as oil reservoirs, and the modified 8 Since hard intermetallic compounds are crystallized in the surface layer, the sliding member exhibits high wear resistance, and therefore, according to the method of the present invention, a sliding member with excellent seizure resistance and wear resistance can be obtained. Can be done. In addition, according to the method of the present invention, since a layer with excellent wear resistance is formed and covered only on the surface layer of the part that slides with the counterpart I, the cost is lower than when the entire member is made of a wear-resistant material. In addition, since there is a high degree of freedom in selecting the component composition of the base material, properties required for the base material other than wear resistance can be easily satisfied.

Furthermore, according to this optical method, by adjusting the type of hydrogen-containing metal component element or alloying ratio in the alloyed metal hydride, pores in the surface layer can be crystallized. The nature and type of intermetallic compound can be easily controlled, and therefore appropriate seizure resistance and wear resistance can be imparted according to the required properties.

[Brief explanation of the drawing]

1 to 3 are schematic cross-sections and diagrams showing step-by-step an example of a situation in which the method of the present invention is implemented. DESCRIPTION OF SYMBOLS 1... A2 alloy base material, 2... Titanium hydride powder fixed layer, 5... Alloying (surface modification layer). Applicant Toyota Jishushushin Co., Ltd. Agent Patent Attorney Takashi 1) Takehisa (and 1 other person)

Claims (1)

[Claims] A metal hydride that can form an intermetallic compound with Al is alloyed on the surface layer of a base material made of an Al alloy using high-density energy, thereby crystallizing the intermetallic compound in the surface layer. A method for manufacturing an Al alloy sliding member, characterized in that the porosity in the surface layer is set to 2 to 30% by hydrogen gas generation accompanying the decomposition of metal hydride.