Addition of molybdenum disulfide solid lubricant to WC-12Ni thermal spray cemented carbide powders through electroless Ni-MoS2 co-deposition

Molybdenum disulfide solid lubricant was added to thermal spray WC-12Ni powders through electroless Ni-MoS₂ co-deposition. With varying the concentration of WC-12Ni and MoS₂ particles in the plating bath, varied concentration of MoS₂ can be controlled in the powder surface layer and the incorporation mechanism of MoS₂ into the shell was discussed as well. The thickness of the Ni-MoS₂ coatings as well as the MoS₂ distribution structure were characterized with a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). The phase structure of the co-deposited coatings was characterized with X-ray diffraction (XRD). It is found that MoS₂ particles can be co-deposited with Ni to form a Ni-MoS₂ composite layer on WC-12Ni powders when effective Ni electroless deposition occurs, since Ni or Ni²⁺ can encapsulate MoS₂ particles to facilitate its incorporation. The content of MoS₂ in the coating increases with increasing the concentration of MoS₂ in the plating bath, or with decreasing the concentration of WC-12Ni powders in the bath which results in increased thickness of deposited Ni- MoS₂ layers. The Ni-MoS₂ coated WC-12Ni powders obtained with the electroless co-deposition process can be used for high velocity oxy-fuel spraying (HVOF) with a proper size and adequate fluidity, and are expected to suppress desulfurization and decarburization effectively.