The preparation and characterization of vanadium carbide coating on 3Cr13 steel by thermal diffusion process with fluoride salt bath

Abstract:

The composition hardness and morphology of vanadium carbide(VC) coatings and their growth kinetics have been investigated by X-ray diffractometer (XRD), the electronic probe microanalysis(EPMA) scanning electron microscope (SEM), vickers indenter and energy dispersive X-ray spectrometry (EDX) on the 3Cr13 stainless steel, which was treated by FLiNaK salts for different time by the thermal diffusion carbide coating process (TD). It was found that VC coatings with the thickness of 3~5 μm formed on the surface of 3Cr13 stainless steel for different treatment time . The coatings displayed petal-shaped and contained a handful of Si and Fe.The average hardness of the VC coating up to 3222 HV and there was a parabola relationship between the thickness of the coatings and the treatment time. VC coatings were covered by rimous SiO₂ phases with the thickness of hundreds of nanometers. The cracks of SiO₂ phases resulted from the tensile stress during the cooling process,which derived from the different thermal expansivity between VC coating and SiO₂ phase. The present study also indicated the potential application of FLiNaK salts in TD process.

Key words:FLiNaK; thermal diffusion carbide coating process; 3Cr13 stainless steel; VC