后处理工艺对激光选区熔化Hastelloy-X合金微观组织及力学性能的影响

Effect of Post Treatment Process on Microstructure and Mechanical Behaviour of Hastelloy-X Alloy Produced by Selective Laser Melting

采用激光选区熔化技术制备了Hastelloy-X合金,并进行了热处理和热等静压工艺,研究不同后处理工艺下合金的微观组织、高温拉伸性能和低周疲劳性能,并对疲劳失效机理进行分析。结果表明:沉积态样品中存在较多的未熔粉、气孔和微裂纹等缺陷,热处理工艺对该类缺陷无明显改善,热等静压工艺可以很好地消除沉积态中存在的缺陷,合金的相对致密度提升至99.9%;热处理后,合金在815℃下的抗拉强度和塑性较沉积态有一定的提升;热等静压后,合金的抗拉强度下降,塑性提升;热处理后合金的低周疲劳寿命仅为热等静压后合金的一半;合金中的未熔粉和夹杂物所在位置是疲劳裂纹源形成的主要位置,热等静压工艺可以很好地消除合金的内部缺陷,大大提高样品的疲劳寿命。

Hastelloy-X alloy manufactured by selective laser melting was treated by heat treatment and hot isostatic pressing process,so as to study the microstructure,high-temperature tensile properties and low cycle fatigue properties under different post treatment processes,and the fatigue failure mechanism was analyzed.Results show that there are many defects such as unmelted powder,pores and microcracks in as-deposited Hastelloy-X samples.These defects have no obvious improvement after heat treatment,which can be eliminated after hot isostatic pressing,and the relative porosity of Hastelloy-X alloy is increased to 99.9%.The ultimate tensile strength and elongation at 815℃have a certain improvement after heat treatment.And the ultimate tensile strength of HIP-processed specimen is decreased,but the elongation is increased.The fatigue life of HT-processed specimen is half of HIP-processed.The location of unmelted powder,inclusion and other defects in Hastelloy-X alloy is the main sites for the fatigue crack source.The HIP process can eliminate the inner defects in Hastelloy-X alloy and improve fatigue life greatly.