电子束选区熔化制备TiAl合金叶片热冲击失效机理

Thermal shock failure mechanism of TiAl alloy blade prepared by SEBM

电子束选区熔化(selective electron beam melting,SEBM)增材制造技术在制备具有低室温塑性的金属间化合物材料方面具有独特的技术优势,采用该技术制备的TiAl合金部件已经在先进航空发动机获得成功应用。本研究以Ar气雾化的Ti-48Al-2Cr-2Nb预合金粉末为原料,采用SEBM成功制备出TiAl合金低压涡轮导向叶片模拟件,并对叶片的抗热冲击性能及随炉试棒的室温拉伸性能进行评价。结果表明:SEBM制备的TiAl合金经热处理后室温抗拉强度可达515 MPa,断后伸长率为1.13%;TiAl合金叶片模拟件经700℃水淬热冲击120次后结构完整,经900℃水淬热冲击6次后叶身部分出现垂直于径向的裂纹;结合裂纹扩展路径和裂纹断口分析,确定叶片部件在热冲击条件下失效的主要机制是表面较大粗糙度引起的应力集中。

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.