Thermal shock failure mechanism of TiAl alloy blade prepared by SEBM

Selective electron beam melting (SEBM), which is a powder-bed fusion additive manufacturing technology has unique advantages in the preparation of intermetallic materials with low room temperature plasticity. Recently TiAl alloy parts prepared by SEBM have been successfully used in advanced aeroengines. In this study, crack-free TiAl alloy low-pressure turbine blade simulation parts were prepared by SEBM using Ti-48Al-2Cr-2Nb powder. The tensile properties of the samples at room temperature and the thermal shock resistance of the blades were evaluated. The results indicate that the room temperature tensile strength of TiAl alloy prepared by SEBM can reach 515 MPa after heat treatment, and the elongation after failure is 1.13%. No cracks are found after 120 cycles of thermal shocks at 700 °C tested by the water quenching. The crack perpendicular to the radial direction is appeared in the aerofoil position after 6 times of accelerated thermal shocks tested at 900 °C. Combined with the analysis of crack propagation path and crack fracture, it is determined that the main mechanism of blade component failure under thermal shock conditions is due to the stress concentration caused by the large surface roughness.