Microstructure, interface characteristics and tribological properties of laser cladded NiCrBSi-WC coatings on PH 13-8 Mo steel

Multiple NiCrBSi-WC coatings with good macro morphology and uniform microstructure were manufactured on PH 13-8Mo steel substrate using laser cladding (LC) technology. Microstructure, interface characteristics and tribological properties of the laser cladded NiCrBSi-WC coatings were researched utilizing optical microscope (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) unit. In XRD pattern of the NiCrBSi-WC coatings, gamma-(Ni, Fe) solid solutions with numerous secondary carbides and intermetallic compounds can be found including W2C, Ni3B, and M23C6. Cooling rate of this LC process can be determined as 1.5 x 10(6) K/s. Ultra-high hardness secondary carbides evenly distributed in the fine gamma-(Ni, Fe) columnar dendrites can be observed in the coatings. From top of the coatings to the substrate, the averaged microhardness of the coatings, dilution area, heat-affected zone and substrate is 1008 +/- 48.2 HV0.2, 842 +/- 31.8 HV0.2, 386 +/- 24.4 HV0.2, 356 +/- 3.0 HV0.2, respectively. The coatings presented the best tribological properties with the lowest average coefficient of friction (COF = 0.28) and the wear rate (3.92 +/- 0.72 x 10(-6) mm(3)/(N.m)). A step feature can be observed in the dynamic stable wear process of the interface at the coating/substrate. Good tribological performances of the interface at the coating/substrate with low average COF (0.40) and wear rate (31.83 +/- 2.12 x 10(-6) mm(3)/(N.m)) can be obtained.