An Investigation of Improving Wear of 390 Die-cast Aluminum Through Hardcoat Anodizing An Investigation of Improving Wear of 390 Die-cast Aluminum Through Hardcoat Anodizing

by Whiting, Michael J

The objectives of this research were to investigate the wear that occurs on the surface of a Hardcoat anodized die-cast aluminum surface, which was sliding against a composite rubber belt. This research investigated known wear theories and the results for previous testing to understand the mechanisms that were likely occurring in this application. These theories indicated that the wear occurring may be reduced by changing the hardness of the materials involved. Archard’s equation gave tangible evidence of this fact, but related to the base material and not a surface coating. It was hypothesized that Hardcoat anodizing would follow the theory of Archard’s equation and increase the wear resistance of 390 die-cast aluminum when sliding against a composite rubber belt. Standardized wear tests were implemented in order to test this theory.

The results of the wear tests indicated that the wear resistance of the Hardcoat anodized coating did not follow the wear theories and wore at a higher rate than the base material surfaces. This is likely due to the phenomenon seen by Jiang and Arnell where the surface roughness influenced the wear rate of DLC coatings. They found that there existed a transition point where the wear rate of the surface increased with an increase of surface roughness. The Hardcoat anodized surface was rougher than the surface of the base material due to alloy materials and the processing characteristics of 390 Aluminum die-casting material. Subsequently the Hardcoat anodized surface wore at a higher rate than did the base surface.

A case study was conducted on an ATV to investigate the accuracy of the results from the laboratory testing. This case study showed a significant localized wear groove in the stock CVT drive sheave with little wear occurring elsewhere. The Hardcoat anodized CVT drive sheave did not show evidence of a significant localized wear groove as the stock sheave but indicates that wear occurred more evenly across the surface. This wear is evident due to visible aluminum through the Hardcoat layer. In addition, there was a ridge at the outer diameter of the sheave where the belt could not wear the surface. Both of these items indicated that significant wear occurred on the surface, but the presence of a localized wear groove is non-existent.