Quality enhancement of crack-free laser-cladded NiCrSiBC-WC coating by in-situ temperature field assistance (ITFA) and post-laser remelting (PLR)

Abstract

WC/Ni-based composite coatings have received much attention in recent years. However, the application of laser cladded WC/Ni-based coatings encounters many issues, such as WC particle distribution inhomogeneity and coating cracking. In this study, the integrated method of in-situ temperature field assistance and post-laser remelting (ITFA+PLR) is proposed for NiCrSiBC-WC coating preparation and compared with mere ITFA and PLR. The results show that the three methods eliminate cracks and enhance overall mechanical qualities, outcompeting the single laser cladding process even with higher WC concentration. ITFA helps the interfacial reaction of the WC particles, while PLR distributes large-sized WC particles and produces and disperses refined carbides. With this, ITFA+PLR combines their benefits and achieves a uniform distribution of fine carbides and original WC. When the phases are analyzed, the relationship between microstructure (i.e., large-sized WC and fine carbides) and coating hardness is quantified and established, yielding a generalized microhardness index. With this unitless microhardness index, it is discovered that the increased density of fine carbides dominates the hardness increase. In summary, ITFA+PLR promotes fine carbide formation, improves its distribution, and obtains the highest hardness for NiCrSiBC-WC coating. With the generalized carbide phase-determined microhardness index, this paper guides the design of crack-free WC/Ni-based coatings and enlightens the improvement of NiCrSiBC-WC coating's mechanical properties.