Improvement of the Cavitation Erosion Resistance of Ti-6Al-4V Through Laser Alloying Titanium Aluminide Based Intermetallic Matrix Composites

摘要

γ-TiAl and α{sub}2-Ti{sub}3Al intermetallic matrix composites (IMC) with TiC reinforcement was laser alloyed on a Ti-6Al-4V substrate. Two different starting powder mixtures based on Al-VC and Al-Cr{sub}3C{sub}2 was used to improve the toughness and ductility of the matrix. In one of the powder mixtures, Al-VC, the laser process parameters were varied to produce γ-TiAl/α{sub}2-Ti{sub}3Al and a{sub}2-Ti{sub}3Al matrix in the surface of Ti-6Al-4V. The coatings were characterised by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and energy-dispersive spectroscopy (EDS). The cross-sectional microhardness of the tested specimens was measured before and after cavitation to identify any work hardening. In a vibratory cavitation erosion test the alloyed layer, which contains predominantly α{sub}2-Ti{sub}3Al in the matrix showed an improved erosion resistance by a factor of up to 5.2. Preferential removal of more brittle γ-TiAl in the multi-phase γ-TiAl/α{sub}2-Ti{sub}3Al IMC coating is believed to have a destructive influence on the coating performance. Over the range of process parameters investigated, an improvement in hardness favours a high erosion resistance. All alloyed layers failed by brittle fracture with varying severity.