Direct laser cladding of layer-band-free ultrafine Ti6Al4V alloy

Abstract

Abstract Ti6Al4V alloy was fabricated on pure titanium substrate using laser cladding. The effect of scanning speed on microstructure, hardness and wear performance of the Ti6Al4V cladding was investigated. The layer-band-like zone, which consists of coarse basket-weave microstructure with short-lamellar α phase and β phase, decreases with the increase of scanning speed. Layer-band-free cladding is obtained at a high scanning speed. With the increase of the scanning speed, the microstructure of the cladding evolves from lamellar or lath-like α/α′ phase to refined acicular α/α′ phase. The ultra-fine microstructure with submicron scaled acicular α/α′ phases (60–400 nm in width) and β phase is obtained under the scanning speed of 600 mm min − 1 . The clad exhibits a high hardness of 7.6 GPa, a high elastic modulus of 136.4 GPa, a reduced friction coefficient of 0.46 and a low wear loss of 0.5 mg in dry sliding wear tests. The main worn mechanisms are fatigue and abrasive wear. A rational high scanning speed is beneficial to the enhancement of wear performance of the Ti6Al4V cladding, due to the obtained ultra-fine microstructure, high residual stress, high hardness and fatigue strength.