Process for lubrication-treating aluminum or aluminum alloy material

Abstract

A lubrication-treating process for an Al or Al alloy material is carried out by cleaning the material; applying an anodic oxidation to the cleaned material surface to form a 3 to 30 mum thick anode oxidation coating; and forming a lubrication coating including a polyester resin (30 to 70 mass parts), a particulate PTFE (30 to 70 mass parts) and ceramic (alumina) particles (0.5 to 5 mass parts), and 2 to 20 mum thick, to thereby impart excellent resistances to adhesion and seizure, and a low friction, to the Al or Al alloy material at a low cost and with no or a very low pollution of the environment.

Description

BACKGROUND OF INVENTION[0001] (1) Field of the Invention[0002] The present invention relates to a process for lubrication-treating an aluminum or aluminum alloy material. More particularly, the present invention relates to a process for lubrication-treating aluminum or an aluminum alloy material such as, for example, an aluminum or aluminum alloy sliding material to form a wear-resistant composite coating on the surface of the material. The process of the present invention is applied to productions of high wear-resistant sliding materials, for example, pistons and scrolls for compressors of air conditioners.[0003] (2) Description of the Related Art[0004] Generally, sliding materials are required to have a low friction property to prevent an energy transfer loss. Also, when a load is applied to the sliding material, an important property of the sliding material is high load-resistance to prevent a seizure of the sliding material under a high face pressure. Also, from an industrial vi...

AI Technical Summary

Benefits of technology

[0024] In the process of the present invention, the lubrication coating is formed on the front surface side of the aluminum or aluminum alloy material. A main purpose of the lubricating coating is to decrease friction between the aluminum or aluminum alloy material and a metallic material on which the aluminum or aluminum alloy material slides during a sliding operation. In the process of the present invention, the thickness of the lubrication coating is controlled in the range of from 2 to 20 .mu.m, preferably from 6 to 14 .mu.m: If the thickness of the lubrication coating is less than 2 .mu.m, the resultant layer exhibits an insufficient friction-reducing effect and thus an unsatisfactory sliding property. If the thickness of the lubrication coating is more than 20 .mu.m the friction-reducing effect is saturated and the coating cost becomes high, and thus an economical disadvantage occurs.

[0027] Further, the ceramic particles are used to enhance the resistance to seizure of the lubrication coating. When a seizure occurs on the lubrication treated aluminum or aluminum alloy sliding material produced by the process of the present invention, the lubrication coating is destroyed and then the anodic oxidation coating is destroyed by a metallic material on which the sliding material slides, to such an extent that the aluminum or aluminum alloy material comes into dry contact with the metallic material. Thus, the total resistance of the aluminum or aluminum alloy sliding material to the seizure can be enhanced by enhancing the seizure resistance of the lubrication coating and thus the total durability of the lubrication-treated aluminum or aluminum alloy sliding material can be improved.

[0029] The thickness of the lubrication coating can be controlled by controlling the coating amount of the aqueous treatment liquid. If the baking temperature is lower than 100.degree. C., an undesirable long time may be necessary to complete the baking procedure. Also, if the baking temperature is higher than 250.degree. C., the polyester resin may be undesirably deteriorated. If the baking time is less than one minute, the baking procedure may not be sufficiently completed. If the baking time is more than 20 minutes, the baking effect may be saturated and the productivity of the target product may be reduced. To enhance the drying effect in the lubrication coating-forming procedure, a pre-heat treatment of the anodic oxidation-treated sliding material to a temperature of 80 to 12.degree. C. may be effectual.

[0050] A treated specimen to be tested was brought into contact with a non-treated aluminum collar (ADC10, an inside diameter: 23 mm, an outside diameter: 25 mm), the sliding faces of the specimen and collar were coated with a lubrication oil; and then the specimen and collar were rubbed against each other under a load of 50N at a rubbing speed of 2 m / second. The load was increased by 50N each 2 minutes after, and the load under which a seizure of the specimen with the collar occurred was determined. The higher the seizure-generating load, the higher the seizure resistance of the specimen.

Problems solved by technology

However, a plated tin layer is soft and thus exhibits a poor durability (a poor wear resistance).

Also, in general, there are problems that materials having a complicated form and surface are difficult to uniformly plate and the plating cost is generally high.

Also, this treatment is disadvantageous in that since the treatment liquid contains a large amount of a fluorine compound, a load for purifying the waste water from the treatment is high and thus a problem of the preservation of the global environment occurs.

In these methods, however, the close adhesive property of PTFE to the anodic oxidation coating layer formed on the aluminum or an aluminum material is low, and thus the PTFE layers formed by the above-mentioned methods are unsatisfactorily close-bonded to the anodic oxidation layer on the aluminum or aluminum alloy material.

However, the PTFE layer per se is soft and easily worn and thus a problem that the PTFE layer is unsatisfactory in durability occurs.

This method causes a problem that a harmful vapor of the organic solvent is diffused into the air atmosphere.

If the thickness of the anodic oxidation coating is less than 3 .mu.m, the resultant lubrication treated material exhibits an insufficient wear resistance.

Also, if the thickness of the anodic oxidation coating is more than 30 .mu.m, while the performance of the resultant material is saturated, the treatment cost is too high, and thus an economical disadvantage occurs.

If the thickness of the lubrication coating is more than 20 .mu.m the friction-reducing effect is saturated and the coating cost becomes high, and thus an economical disadvantage occurs.

If the baking temperature is lower than 100.degree. C., an undesirable long time may be necessary to complete the baking procedure.

Also, if the baking temperature is higher than 250.degree. C., the polyester resin may be undesirably deteriorated.

If the baking time is less than one minute, the baking procedure may not be sufficiently completed.

If the content of the polyester resin (A) is less than 30 parts by mass on the basis of (A)+(B)+(C)=100 parts by mass, the binding effect of the polyester resin (A) in the lubrication coating may be insufficient and, thus, a firm lubrication coating may not be formed.

Also, if the content of the polyester resin (A) is more than 70 parts per 100 parts of the total (A)+(B)+(C), the content of the particulate polytetrafluoroethylene (B) becomes too low, and thus the resultant coating may exhibit an insufficient lubrication effect.

If the content of the particulate polytetrafluoroethylene is less than 30 parts per 100 parts of the total (A)+(B)+(C), the resultant coating may exhibit an insufficient lubrication effect.

Also, if the content of the particulate polytetrafluoroethylene is more than 70 parts per 100 parts of the total (A)+(B)+(C), the resultant lubrication coating contains polyester resin in an insufficient content, and thus the binding effect of the polyester resin may become insufficient, and the resultant lubrication coating may exhibit an insufficient mechanical strength.

Further, if the content of the ceramic particle is less than 0.5 parts per 100 parts of the total (A)+(B)+(C), the resistance to seizure of the resultant lubrication coating may be insufficient, and if the content of the ceramic particles is more than 5 parts, the resultant lubrication coating may have an insufficient continuity, and thus may exhibit an insufficient mechanical strength.

If the particle size is less than 0.01 .mu.m, the particles are too fine and the resultant lubrication coating may exhibit an insufficient seizure resistance.

Also, if the particle size is more than 0.2 .mu.m, the resultant particles may easily agglomerate with each other and, as a result, the resultant lubrication coating may have an insufficient continuity and undesirable local adhesions of the lubrication coating may occur.