The synergistic action of Ag and MoS2 on tribological properties of Al2O3/Ag(MoS2) composite coatings

Based on the inherent pores and cracks inside of Al2O3 coating and Al2O3/Ag coating which were sprayed by atmospheric plasma spraying technology, Al2O3/MoS2 and Al2O3/Ag/MoS2 composite coatings were manufactured by means of the vacuum impregnation and in-situ hydrothermal synthesis in this study. The microstructure and mechanical properties of Al2O3(MoS2) coating and Al2O3/Ag(MoS2) coating were analyzed. The synergistic action of Ag and MoS2 on the tribological properties of Al2O3(MoS2) and Al2O3/Ag(MoS2) coatings was discussed in detail. There were more defects and holes inside of Al2O3/Ag coating than Al2O3 coating, so the mechanical properties and wear rate of Al2O3/Ag coating were poorer than those of Al2O3 coating. Al2O3/MoS2 coating showed the great lubricating effect, but this effect cannot maintain a long time since the lubricating substance MoS2 would be consumed under repeat frictional action. The combined introduction of Ag and MoS2 into the defects inside of Al2O3/Ag/MoS2 coating not only reduced the wear rate, but also enhanced the lubrication effect further. The synergistic action of Ag and MoS2 could bring the excellent long-time lubricating effect to Al2O3/Ag/MoS2 composite coating effectively due to the formation of continuous lubricating film.