HARDNESS AND WEAR BEHAVIOUR OF TIC-AL/SI COMPOSITE COATINGS MADE BY LASER CLADDING ONTO AL SUBSTRATE

摘要

This study investigates the influence of thecomposition and microstructure of laser cladded metalmatrixcomposite (MMC) coatings onto the hardnessand the adhesive wear behaviour. Laser cladding wascarried on pure Al substrate using a cw Nd:YAG laserand a coaxial powder injection system. Compositecoatings were made of an Al/Si matrix containing 0 to40 wt.% Si and a TiC reinforcement powder with avolume fraction ranging form 0 to 30 %. Samples werecharacterised using an optical microscopy, XRD,hardness measurement and adhesive wear testing (ballon-disk device). Si content and TiC reinforcement ratioincreased the bulk coating hardness up to a maximumvalue of 250 HV5. For a fixed TiC ratio, a linearcorrelation was observed between hardness and Sicontent. Depending on the TiC volume fraction and Sicontent, the wear behaviour appeared a mild, severe orsurface fatigue wear. Hypoeutectic Al/Si alloyswithout TiC reinforcement showed a severe weardominated by extensive plastic flow and significantwear scars. With the TiC addition, a mild wear,characterized by a low wear rate and a fine damage,was observed. In the case of hypereutectic alloyswithout TiC reinforcement, wear was also mild and thewear rate was similar to the one observed on Al-12Si/30 vol.% TiC coating. Addition of TiC reinforcementsaccelerated the wear of these hypereutectic alloys dueto the surface fatigue.