Quickly-Formed Self-lubricating Hard Coating On Surface Of Aluminum Alloy

In order to improve lubricating performance of the coating, one method to quickly form hard self-lubricated coating on the surface of aluminum alloy was provided in this paper, and by co-precipitation, MoS₂ particles precipitated into the hard oxide coating during hard oxidation of aluminum alloy. It was studied by cross experiment that the effect of both compositions, in mixed electrolyte of sulfur acid (more) and oxalic acid, and process parameters on the forming process of the coating, including its performances. Through SEM and EDS, the microstructure of the self-lubricated coating was investigated, and distribution of MoS₂ in the coating was tested respectively. Anti-oxidation performance, hardness, wearing performance as well as other performances of the coating was analyzed by salt spray experiment, non-destructive thickness meter, micro-hardness instrument, and micro-friction tester respectively.It showed that, through EDS test, there was uniformly distributed such elements as Al, O, Mo, S, etc in the film coating co-precipitated, and total quantity of both Mo and S occupied 10%. As a result of friction test, the friction coefficient of the film prepared by co-precipitation is 0.2, much less than that of hard oxidation film 0.9, which proved further the existence of MoS₂ in the film coating and it improved lubricating performance. Thickness test showed that the growth of the film coating will be markedly quicker by both applying double impulse current and adding additives, and the quickest forming speed is 4μm per minute. SEM result indicated that hole in the film coating co-precipitated is small and lesser. It showed by hardness test that micro hardness was improved not too much, while anti-oxidation performance is direct ratio to thickness of the film by salt spray experiment.