Influence of Previous Particle Boundary on high-temperature strengths of PM superalloy

已知PPB（先验颗粒边界）会降低PM合金的韧性和延展性。锻造工艺一般采用HIP烧结后，粉碎粉末表面杂质造成的PPBs。等离子体旋转电极工艺（PREP）能够减少耐火金属粉末中的杂质。为了降低PPBs，本研究将PREP应用于718合金粉末中。在δ亚溶剂温度下对合金粉末进行热处理，获得了超细晶粒和高强度。研究了PREP处理对P/ m718拉伸性能和显微组织的影响。经PREP处理后，粉末中的杂质减少。发现PREP增加了烧结试样的密度。然而，由于PPB中氧含量和细沉淀物的减少不足，它并没有像预期的那样提高延展性。

PPB (prior particle boundary) is known to decrease the toughness and ductility of PM alloys. The forging process is generally applied after sintering by HIP to crush PPBs, which are caused by impurities on the surface of the powder. The PREP(Plasma Rotating Electrode Process) is known to capable of reducing impurities in refractory-metals powder. In this study, to reduce PPBs, PREP was applied to alloy 718 powder. The alloy powder was HIPed at a delta-subsolvus temperature to achieve a superfine grain and high strength. The influence of PREP treatment on tensile properties and the microstructure of P/M 718 were investigated. After PREP treatment, the impurities in the powder were reduced. The PREP was found to increase the density of the sintered specimen. However, it did not improve ductility as expected due to an insufficient reduction of the oxygen content and fine precipitates in PPB.