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• Enhanced wear-resistance were achieved by reducing the content of Nb in TiZrHfNb. • The wear loss is related to the subsurface instabilities during friction. • Deformation-induced grain refinement and phase transformation enhance wear-resistance. A sliding enhanced wear-resistance can be significantly achieved by reducing the content of Nb element in TiZrHfNb refractory high entropy alloys (RHEAs). The wear loss reduced by half from TiZrHfNb to TiZrHfNb 0.4. The wear loss is directly related to the subsurface instabilities induced by plastic deformation during friction. The origins can be attributed to two factors: i) plastic deformation induced grain refinement; ii) deformation-induced BCC to HCP phase transformation. [ABSTRACT FROM AUTHOR]

The wear behaviors of γ-TiAl alloy with two typical microstructures, i.e., the lamellar colony microstructure (denoted as the HIPed sample) and the fine equiaxed microstructure (denoted as the heat-treated sample), were thoroughly studied during dry sliding test to resolve the microstructural feature dependence of wear mechanisms. Special efforts have been made to the subsurface stability during sliding by using electron backscatter diffraction (EBSD) techniques. It is demonstrated that both cases present a similarity in the friction coefficients but a disparity in the wear loss. The lower wear loss was achieved in the case of HIPed sample. This can be attributed to the various directions in the local strain induced by plastic deformation during sliding, the crystallographic structure and the coherent interface in the lamellar colony, leading to high resistance ability to the wear. For the case of heat-treated sample, the high plastic deformation ability in the α 2 grains along the surface and the equiaxed morphology generate to high ability to plastic deformation and sliding during friction, contributing to the high wear loss. However, the heat-treated sample presents a high subsurface structure stability according to the local misorientation analysis. The present results provide new information on wear mechanisms of γ-TiAl alloy and may offer a method to enhance its wear resistance by tailoring the microstructural features. • The wear loss in a dry sliding of a γ-TiAl alloy is evidenced to connect with microstructural feature. • Special efforts have been made to the subsurface stability during sliding by using EBSD techniques. • The lower wear loss was achieved in the case of the lamellar colony microstructure. • The fine globular microstructure presents a high subsurface structure stability. [ABSTRACT FROM AUTHOR]