Evolution of microstructure and mechanical properties of Co-SiC tungsten inert gas cladded coating on 304 stainless steel

Abstract

In this work, Silicon carbide (SiC) reinforced Cobalt (Co) coatings were produced using tungsten inert gas (TIG) coating technique on AISI 304 stainless steel substrates. The effects of various heat inputs on microstructure, wear resistance, coefficient of friction (COF), and microhardness, of composite coatings were systematically investigated. Results of X-ray diffraction (XRD) showed that the composite coatings were primarily composed of FeSi, CoSi, CoSi2, Fe3C, SiC and Co phases. Analysis of the elements by using energy dispersive X-ray spectroscopy (EDX) confirmed the existence of elements Co, C, Si, Ni, and Fe in the coating. The microstructural analysis was performed using scanning electron microscopy (SEM), micrographs showed that grains changed from an irregular polygonal grain to an elongated dendritic grain depending on heat inputs. Composite coating produced at 528 J/mm heat input shows uniformly distributed fine dendritic grains and produces defect-free coatings. The average maximum microhardness of composite coating was increased from ~374 HV0.1 to ~650 HV0.1, whereas the average microhardness of the 304-steel substrate was ~190 HV0.1. Comparative wear resistance of Co-SiC composite coating was appreciably improved, ranging from ~1.7 to ~6.4 times better than that of the AISI 304 stainless steel substrate. At 528 J/ mm heat input, composite coating exhibits the best tribological properties with reduced COF (~0.40) compared to the substrate.