Microstructure, microhardness and corrosion resistance of Stellite-6 coatings reinforced with WC particles using laser cladding

• Increase in laser beam power causes reduced content of primary WC in coatings.
• WC carbides in MMC coatings were well bonded to the matrix.
• Increased content of WC in powder mixture leads to Cr reduction in the matrix.

The paper presents the method of preparation and study results of metal matrix composite coatings (MMC coating) in the system of Stellite-6 and tungsten carbides. Changes in microstructure, corrosion resistance, microhardness, phase and chemical composition as well as surface conditions were investigated. Stellite-6/WC MMC coatings were prepared by laser cladding technology using a 1 kW continuous wave Yb:YAG disk laser with a powder feeding system. Two different powder mixtures containing 30% and 60% of WC and three different values of laser beam power were used. It was found that increasing WC values caused an increase in microhardness on the cross-section of the produced coating in comparison to the substrate. Depending on the laser beam power, the coatings produced with 30% WC achieved microhardness in the range from about 350 HV0.05 (700 W) to about 680 HV0.05 (550 W). Twice as large amount of WC particles in the powder mixture resulted in increase of microhardness from about 700 HV0.05 (700 W) to about 1500 HV0.05 (550 W). In the coating M7C3, M6C and M23C6 carbides were identified by an X-ray diffraction method. Special attention was given to bondings between carbide particles and metal matrix, which had a characteristic microstructure. A reduction of corrosion resistance with increasing WC content in coating was also discovered.