Abstract
The CrS/NbC Co-based self-lubricating composite coatings were successfully fabricated on Cr12MoV steel surface by laser clad Stellite 6, WS2, and NbC mixed powders. The phase composition, microstructure, and tribological properties of the coatings ware investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS), as well as dry sliding wear testing. Based on the experimental results, it was found reactions between WS2 and Co-based alloy powder had occurred, which generated solid-lubricant phase CrS, and NbC play a key role in improving CrS nuclear and refining microstructure of Co-based composite coating during laser cladding processing. The coatings were mainly composed of γ-Co, CrS, NbC, Cr23C6, and CoCx. Due to the distribution of the relatively hard phase of NbC and the solid lubricating phase CrS, the coatings had better wear resistance. Moreover, the suitable balance of CrS and NbC was favorable for further decreasing the friction and improving the stability of the contact surfaces between the WC ball and the coatings. The microhardness, friction coefficient, and wear rate of the coating 4 (Clad powders composed of 60 wt % Stellite 6, 30 wt % NbC and 10 wt % WS2) were 587.3 HV0.5, 0.426, and 5.61 × 10−5 mm3/N·m, respectively.
Highlights
The lubricating and tribological property of moving components under extreme conditions such as high temperature, heavy load, vacuum, and humid and dry air environments seriously affect their reliability and service time of the entire system [1,2]
Previous research [14,16,17] has shown that WS2 decomposed and oxidized when it was used as solid lubricant additives to fabricate metal matrix self-lubricating coatings (MMSCs) by laser cladding
Lu et al [19] fabricated the Ti2 CS/CrS MMSC by laser clad NiCr/Cr3 C2 -WS2 mixed powders; the results indicated that the composite coating presented excellent self-lubricating properties due to the formation of the lubricious CrS and Ti2 CS sulfides
Summary
The lubricating and tribological property of moving components under extreme conditions such as high temperature, heavy load, vacuum, and humid and dry air environments seriously affect their reliability and service time of the entire system [1,2]. Lu et al [19] fabricated the Ti2 CS/CrS MMSC by laser clad NiCr/Cr3 C2 -WS2 mixed powders; the results indicated that the composite coating presented excellent self-lubricating properties due to the formation of the lubricious CrS and Ti2 CS sulfides. Among those studies, the friction-reducing role of self-lubrication phases (such as TiS, Ti2 CS, and CrS) has been investigated in detail and the formation mechanism of CrS is involved. The microstructure and wear performance of those coatings are presented and discussed
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