增材制造HX合金喷嘴微观组织及缺陷控制研究

Investigation on Microstructure and Defects Control of Nickel-Based Superalloy Hastelloy-X Obtained by Selective Laser Melting Process

为深入评估增材制造技术在燃气轮机高温部件上实际应用的可行性,对增材制造燃气轮机喷嘴材料的微观组织与缺陷状况进行了研究。研究中采取了典型的金属增材制造技术——选区激光熔化法,使用两种不同粒径规格的粉末,制备了燃气轮机燃烧室喷嘴用镍基高温合金Hastelloy-X(HX)试样及喷嘴样件,分析了沉积态和热等静压态试样的微观组织特征,初步评估了热等静压处理的应用效果,并验证了实际零件打印的可行性。结果显示:沉积态试样的微观组织具有明显的熔池边界、柱状晶以及树枝晶等组织特征,同时其内部存在着微裂纹、气孔、未熔粉等冶金缺陷。通过适当提高能量输入、降低粉末粒径,能够显著减少上述缺陷,提高沉积态试样的相对致密度。此外,热等静压处理工艺能够有效消除熔池界与树枝晶等亚结构,闭合气孔与微裂纹,进一步提高相对致密度,改善沉积态材料塑性。试验结果表明:热等静压后试样室温拉伸性能能够达到Hastelloy-X合金锻件水平。最终使用优化后的工艺和粉末粒径(10~45μm),成功制备了燃烧器喷嘴样件。

In order to evaluate the application feasibility of additive manufacturing(AM)technology in gas turbine industry,an investigation on AMed material’s microstructure and defects was performed.The nickel-based superalloy Hastelloy-X(HX)was selected for selective laser melting(SLM)process,one of typical additive manufacturing technologies,and the related microstructure was analyzed with SLMed and HIPed samples.Except for typical microstructure such as molten pool boundaries,dendrites and columnar grain,it was found that pores,un-melting powder and micro cracks were main kinds of defects in this SLMed alloy.In order to control or eliminate these defects,effects of reducing powder size,increasing energy input and improving post-treatments on the microstructure of SLMed samples were investigated.Result showed that higher relative density(which means fewer defects)could be obtained by using powder with smaller size and appropriate line energy density.In addition,it was proved that hot isostatic pressing(HIP)could improve SLMed ductility by closing pores and cracks combined with eliminating the MPB and dendrites.Tensile test results showed that HIPed samples had a room temperature elongation which even run up to the level of forged alloy.At last,a combustor nozzle prototype was fabricated by optimized SLM process and powder(10~45μm)based on the research results mentioned above.