Liquid phase sintering-based coating of Al2O3/TiC composite layer on cemented carbide

• The Al2O3 and TiC coatings are achieved simultanelously with non vapor method.
• The coating process is combined with the sintering of cemented carbide substrate.
• TiO2 sol transforms to TiC by carbonthermal reducation reaction during sintering.
• Carbon-deficit condition on the surface results in a rounded shape of WC.
• Ti results in the micro multi-stepped microstructure of WC by 3D growth mechanism.

A novel technology is introduced to facilitate the preparation of Al2O3/TiC composite layer on cemented carbide, which is based on liquid phase sintering process other than chemical/physical vapor deposition method. Al2O3/TiO2 sol is dip-coated on cemented carbide green compact, which transforms to crystal Al2O3/TiC by carbothermal reduction reaction during sintering. The surface layer is composed of WC, Co and Al2O3/TiC phases. The reaction creates carbon-deficit condition on the surface and results in the disappearance of Co capping and round-edged WC grains. The WC has micro and multi-stepped microstructure, indicating a 3D growth mechanism. The introduction of Al2O3/TiC is responsible for the layer-by-layer structure other than equilibrium faceted (truncated) triangle prism shape of WC.