Laser cladding of MMC coatings on aluminium substrate: influence of composition and microstructure on mechanical properties

Abstract

The influence of the composition and the microstructure of laser cladded metal matrix composite (MMC) coatings on their mechanical properties (namely hardness and adhesive wear resistance) was investigated in this study. Laser cladding on pure Al substrate was carried out using a continuous wave (cw) Nd:YAG laser and a coaxial powder injection system. Composite coatings were based on an Al metallic matrix bearing a Si content ranging from 0 to 40 wt.% Si and reinforced with TiC particles with a volume fraction ranging from 0 to 30%. The coating microstructure was characterised by optical microscopy and XRD. Mechanical properties of the samples were determined by hardness and adhesive wear testing. The microstructure of the coatings was homogeneous and free of pores or cracks. Carbides were uniformly distributed throughout the coating cross-section. The addition of Si and TiC reinforcement particles increases the bulk hardness of the coatings and strongly influences the wear mechanism. Indeed, depending on the TiC volume fraction and Si content, the coating wear, characterised by a ball-on-disk device, appeared as mild, severe or surface fatigue wear.