A new sight of tribological characterization at high temperature for V doping in Cr2AlC

Abstract

This study synthesized the bulk (Cr_1-xV_x)₂AlC (x = 0, 0.25, 0.5, 0.75) materials by hot-pressed sintering method with the raw materials of Cr, Al, C, and V powders. The mechanical properties and tribological behaviors over a wide temperature range were investigated in detail. The results indicate that the addition of V could enhance the internal energy and micro-stress, hinder the dislocation slip of Cr₂AlC. The hardness, flexural strength, and fracture toughness of (Cr_0.5V_0.5) ₂AlC are 41.0 %, 34.1 %, and 61.7 % higher than those of Cr₂AlC respectively. Notably, the friction tests demonstrate that the solid solution of V could improve the tribological properties of Cr₂AlC at room temperature due to the solid solution strengthening. At medium-high temperatures, on the contrary, the solid solution of V results in the higher friction coefficients compared with Cr₂AlC, which result from the phase of CrVO₄ without lubricating and anti-wear performances formed on the worn surface. When the test temperature reaches 800 °C, the solid solution of V preferentially diffuse to surface, and then be oxided to the AlVO₄, CrVO₄ and V₂O₅. Under the action of thermal-force coupling, AlVO₄ and CrVO₄ decompose to Al₂O₃, Cr₂O₃ and V₂O₅, which endows (Cr_0.5V_0.5) ₂AlC with an excellent self-lubrication performance at 800 °C.