Effects of Y2O3 addition on the microstructure and wear-resistant performance of TiN/TiB-reinforced Ti-based laser-clad coatings on Ti‐6Al‐4V alloys

Abstract

To enhance the wear resistance and further extend the application of Ti alloys under severe wear conditions, TiN- and TiB-reinforced Ti-based composite coatings modified with Y2O3 were fabricated on Ti‐6Al‐4V alloys by laser cladding. The effects of Y2O3 addition on the phase constituents, microstructural characteristics, microhardness, and tribological properties of the coatings were investigated. The phase constituents in the coatings were TiN, TiB, and α-Ti, and remained unchanged after adding Y2O3. The addition of Y2O3 weakened the side-branching tendency of TiN and promoted the morphological conversion of TiB from needles to plates by modifying the local constituents and temperature in the melt pool. With an increase in the Y2O3 content, the microhardness and wear resistance of the coatings first increased and then decreased, which was consistent with the compactness of the microstructure. The superior tribological properties of the coatings were attributed to the increased load-bearing provided by the large-sized TiN and TiB units and the increased load-transfer strength induced by the fine TiB whiskers. The coating fabricated with 1 wt% Y2O3 exhibited the highest microhardness and lowest wear loss, and the wear mechanism it underwent was abrasive wear characterized by micro-cutting. This study demonstrates the possibility of modifying the microstructures of Ti-based composite coatings with Y2O3.