Surface Modification of Aluminum Alloy Using Plasma Based Ion Implantation and Deposition

Abstract

Aluminum alloys are used for mechanical parts, but the alloys have poor wear-resistance. To increase their wear resistance, a hard coating is applied to the surface of the alloys. Diamond-like carbon (DLC) is applied in surface modification technology due to its superior mechanical characteristics. In this study, in order to achieve effective surface modification to improve the wear resistance of the aluminum alloys, a new coatings-system was designed. This coating-substrate system is a multilayer coating-substrate system, which consists of nitriding pretreatment of the substrate, the intermediate layer of the silicon-based film and the outer layer of the DLC film. This new coating-system was used to deposit DLC film on three kinds of aluminum alloys that have different Si contents. In order to determine the influence of the Si contents on the mechanical properties of the DLC film, SEM observation of the cross section of the coating layer, the adhesion and the wear resistance of the layer were experimentally investigated. The results were as follows: (1) In the case of the DLC un-coated aluminum alloys, the rapid progress of the friction coefficient in the case of 10-N load was found at the short sliding distance. (2) The hardness of the DLC film was not decreased with the increase of Si contents. And the increase of Si contents did not have a negative influence upon the hardness of the DLC film. (3) The frictional coefficient of the Al-4%Si alloy was the smallest, the frictional coefficient of the DLC film was decreased with the increase of Si contents, and it was effective for improvement of the frictional coefficient to increase Si contents. The new coating-substrate system is effective for improving the adhesion between the substrate of the aluminum alloy and the DLC film. Moreover, the increase of Si contents was effective for the decrease in the frictional coefficient.