Hardness and wear behaviour of TiC-Al/Si composite coatings made by laser cladding onto AL substrate

Abstract

This study investigates the influence of the composition and microstructure of laser cladded metal-matrix composite (MMC) coatings onto the hardness and the adhesive wear behaviour. Laser cladding was carried on pure Al substrate using a cw Nd:YAG laser and a coaxial powder injection system. Composite coatings were made of an Al/Si matrix containing 0 to 40 wt.% Si and a TiC reinforcement powder with a volume fraction ranging form 0 to 30 %. Samples were characterised using an optical microscopy, XRD, hardness measurement and adhesive wear testing (ball-on-disk device). Si content and TiC reinforcement ratio increased the bulk coating hardness up to a maximum value of 250 HV5. For a fixed TiC ratio, a linear correlation was observed between hardness and Si content. Depending on the TiC volume fraction and Si content, the wear behaviour appeared a mild, severe or surface fatigue wear. Hypoeutectic Al/Si alloys without TiC reinforcement showed a severe wear dominated by extensive plastic flow and significant wear 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 alloys without TiC reinforcement, wear was also mild and the wear rate was similar to the one observed on Al-12Si/30 vol.% TiC coating. Addition of TiC reinforcements accelerated the wear of these hypereutectic alloys due to the surface fatigue.This study investigates the influence of the composition and microstructure of laser cladded metal-matrix composite (MMC) coatings onto the hardness and the adhesive wear behaviour. Laser cladding was carried on pure Al substrate using a cw Nd:YAG laser and a coaxial powder injection system. Composite coatings were made of an Al/Si matrix containing 0 to 40 wt.% Si and a TiC reinforcement powder with a volume fraction ranging form 0 to 30 %. Samples were characterised using an optical microscopy, XRD, hardness measurement and adhesive wear testing (ball-on-disk device). Si content and TiC reinforcement ratio increased the bulk coating hardness up to a maximum value of 250 HV5. For a fixed TiC ratio, a linear correlation was observed between hardness and Si content. Depending on the TiC volume fraction and Si content, the wear behaviour appeared a mild, severe or surface fatigue wear. Hypoeutectic Al/Si alloys without TiC reinforcement showed a severe wear dominated by extensive plastic flow and significan...