Wear Resistance of Surface Treated Aluminum Alloy for Die Casting

Surface treatments were conducted on aluminum alloy ADC 12 by chemical tin plating, electroless nickel plating, molybdenum disulfide coating on zinc phosphating, and hard anodizing. Then, frictional and wear resistances of the above treated surfaces were studied.The results obtained were summarized as follows.(1) These treated surfaces showed particularly lower coefficients of statical friction by preventing adhesion of metallic substances.However, the combinations of the platings of the same kind, such as tin plating with electroless nickel plating, showed higher coefficients of statical friction.(2) Molybdenum disulfide coating had the most remarkable effects on lubrication and tin plating was the second.(3) It was found by wear test that these treated surfaces showed higher wear resistances than those of no treatment.(4) Molybdenum disulfide coating showed the highest wear resistance.(5) Electroless nickel plating and hard anodizing showed the next highest wear resistance. However, these surfaces considerably weared out the other contacting metal when they were combined with other metals. In particular, hard anodizing had remarkable effects.Therefore, it was found that anodizing is not a proper surface treatment if the treated surface is used in combination with a soft metal such as an aluminum alloy.(6) Tin plating was not very effective in surface treatment for rotors, because it gave thin film showing low wear resistance.On the other hand, tin plating was very effective for stators, because of higher wear resistance. The combination of tin plated surface on the stator and molybdenum sulfide coating on the rotor showed higher wear resistance than any other combinations.