Effect of MoS2 content on microstructure and properties of supersonic plasma sprayed Fe-based composite coatings

In this paper, the high chromium Fe-based composite coatings with different mass fractions of MoS2 powders were prepared by supersonic plasma spraying technology. The influence of MoS2 addition on the microstructure, phase composition, hardness, coating-substrate bonding strength, and friction & wear properties was studied. The results show that the interface between the deposited coatings and the substrates exhibited no obvious detachment, and the porosity was reduced with the addition of MoS2. However, the hardness of composite coatings and bonding strength between coatings and substrates were decreased with the increase of MoS2 content. Attributed to the fact the Cr element in Fe-based powder played a role of stabilizing the ferrite phase and deoxygenation, no oxide and phase transformation of α-(Fe, Cr) were detected. The XRD results also revealed that partial decomposition of MoS2 occurred during the spraying process, leading to the formation of Mo. The worn surface morphology analysis showed that the wear mechanism of the Fe-based coating without MoS2 was mainly oxidative wear. Through the evolution of wear mechanism of three composite coatings, it is found that with the increase of MoS2 content, the phenomenon of abrasive & fatigue wear was intensified, owing to the reason that the bonding between Fe-based matrix material and MoS2 in the coating was poor. Therefore, the content of MoS2 should be rationally controlled in order to improve the friction & wear properties.