Preparation and Tribology Performance of Ni-Al-Ag Self-Lubricating Composite Coatings on Aluminum Alloy

Abstract

In order to investigate the existence form of solid lubricant Ag in mechanical ball milling preparation of composite coating and the wide temperature range tribological properties of composite coating，a method of indirectly adding solid lubricant Ag was designed to prepare Ni-Al-Ag self-lubricating composite coating on aluminum alloy surface by mechanical ball milling，and the components，mechanical and tribological properties of the coating were analyzed and characterized.Results showed that the microstructure of the composite coating prepared by pre-ball milling was evenly distributed，and no slip cracks occurred.After heat treatment，different Ni-Al intermetallic compounds were formed in the four composite coatings prepared with four pre-ball milling times (0，6，12，18 h).With the prolongation of pre-ball milling time，the hardness of the coating tended to rise，and the micro hardness of the composite coating after pre-ball milling for 12 h and 18 h was about 250 HV.The friction coefficient and wear rate of the aluminum alloy substrate were about 0.37 and 1.48×10-3mm3/(N·m) at room temperature，and serious adhesion occurred during friction at 200 ℃and 350 ℃.The friction coefficients of the self-lubricating composite coatings prepared by pre-ball milling for 12 h and 18 h were about 0.19 and 0.16 (room temperature)，0.25 and 0.25 (200 ℃)，and 0.27 and 0.25 (350 ℃)，respectively，and the wear rates were (1.5～4.0)×10-4mm3/(N·m).The preparation of self-lubricating composite coating could effectively protect the aluminum alloy substrate at room temperature to 350 ℃，broadening the range of the application temperature of aluminum alloy substrate.

Keywords

• mechanical ball milling|aluminum alloy|composite coating|wide temperature range|tribological properties