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

PPB(先验颗粒边界)会降低粉末冶金合金的韧性和延性。由于粉末表面存在杂质，通常采用热等静压烧结后的锻造工艺来粉碎PPB。众所周知，等离子体旋转电极法能够降低难熔金属粉末中的杂质。在本研究中，为了减少PPbs，在718合金粉末中应用了PREP。合金粉末在亚溶剂温度下进行等静压处理，以获得超细晶和高强度。研究了预热处理对粉末冶金718拉伸性能和显微组织的影响。经过预处理后，粉末中的杂质减少。研究发现，预制棒可以提高烧结体的密度。然而，由于PPB中的氧含量和细小析出物的减少不足，它并没有像预期的那样改善塑性。

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.