Microstructure Characteristics and Tribological Properties of Gradient Cu-MoS2 Self-Lubricating Coating Fabricated by Selective Laser Melting of Ink-Printed Metal Nanoparticles

Self-lubricating coating has been used in industrial applications with severe conditions, such as high temperatures, vacuum, radiation, etc. In this paper, a selective laser melting of ink-printed metal nanoparticles (SLM-IP metal NPs) rapid manufacturing method was applied to fabricate Cu-MoS2 self-lubricating coating. A tailored ink consisting of metal NPs, reductant, and dispersant was deposited on a stainless steel substrate, forming the laminated gradient Cu-MoS2 coating. The microstructure and mechanical properties of the composite coating were characterized. The friction and wear behavior were experimentally investigated by dry sliding wear test at room and higher temperatures (>200 °C). The results indicated that the upper copper sulfur molybdenum compound layer with homogeneously distributed MoS2 provided a significant friction reduction and wear resistance. The SLM-IP Cu-MoS2 coatings showed a reduced friction coefficient by 54% compared to the pure Cu coating. The transitional Cu layer mitigated the abrupt changes in physical properties and enhanced the bonding strength between the coating and substrate. Especially, under the test condition of 200 °C, the Cu-40 vol% MoS2 coating also presented an excellent resistance to oxidation and had a lower friction coefficient of 0.24. This research provides the feasibility of fabricating self-lubricating coatings by the SLM-IP metal NPs method for surface engineering technologies.