热工艺对激光选区熔化Hastelloy X合金组织及拉伸性能的影响

Effect of heat processing on microstructures and tensile properties of selective laser melting Hastelloy X alloy

采用激光选区熔化技术制备Hastelloy X试样,研究热等静压和固溶处理对Hastelloy X试样显微组织及拉伸性能的影响。结果表明:沉积态组织中可观察到熔池形貌、柱状晶及晶内的胞晶结构,无析出物,其拉伸性能表现出高强度低塑性特点,高温拉伸断口沿激光扫描熔化道断裂。经热等静压后,组织演变为等轴晶,晶界及晶内存在较多的析出物,裂纹愈合,试样拉伸强度降低,塑性提升,尤其是高温屈服强度降低了约48%,高温伸长率提升了约59%。经热等静压+固溶处理后,晶粒尺寸及形貌与热等静压态相比近乎无差异,但晶内析出物明显减少,该状态下的综合拉伸性能最优。

The technology of selective laser melting was used to fabricate Hastelloy X samples. The effect of hot isostatic pressing (HIP) and solution treatment on microstructures and tensile properties of Hastelloy X samples was investigated. The results show the as-deposited samples exhibit clear melt pool morphologies, columnar grain with embedded cellular structures and no obvious precipitates are detected. The corresponding tensile properties are characterized by high strength and low ductility. High temperature tensile fracture surface reveals that the as-deposited samples crack along laser scan tracks. After HIP, the microstructures evolved into equiaxed grains, and large amount of precipitates are found to distribute within grain boundaries and grain interiors. Besides, solidification cracks are effectively healed by HIP. In this circumstance, the tensile strength is decreased by about 48% combined with improved ductility up to 59% after high temperature tensile tests. After HIP+solution treatment, the grain size and morphology keep similar with that in HIP processed state, while the amount of precipitates inside grain areas is significantly reduced and an overall sound tensile property is achieved.