EP741NP superalloy was fabricated by laser powder bed fusion (LPBF) and subsequently subjected to different heat treatments including hot isostatic pressing (HIP), solution + aging, HIP + solution + aging. The structural features of the alloy in the as-built condition as well as after heat treatment were studied and compared to its mechanical characteristics such as hardness, tensile strength, impact strength, and compression strength at elevated temperatures. It was found that LPBF samples have a fine-grained columnar-cellular microstructure formed from colonies of primary dendrites and poor mechanical properties caused by structural defects (pores and isolated microcracks). The Laves phases of different compositions (Cr₂Nb, Co₂Nb and Cr₂Hf) were detected in the interdendritic space. HIP contributes to elimination of microcracks, precipitation of the γ′ phase (0.5–7 μm in size), dissolution of the Laves phases, and formation of MeC carbide phases. A combination of these events increases strength and ductility of the alloy. Solution followed by aging without HIP results in formation of the fine-grained γ′ phase with size ranging from 150 nm to 2 μm, elimination of the Laves phases, and precipitation of MeC carbides (Cr₂₃C₆), which enhances strength. Ductility, however, remains low as the alloy structure still contains microcracks. The LPBF samples subjected to combined post-treatment (HIP + solution + aging) exhibit the maximum mechanical properties due to the elimination of structural defects during HIP and formation of the fine-grained γ/γ’ microstructure during solution and aging.

EP741NP超级合金是通过激光粉末床熔合（LPBF）制成的，随后经过不同的热处理，包括热等静压（HIP），固溶+时效，HIP +固溶+时效。研究了合金在建成状态以及热处理后的结构特征，并将其与机械特性（如高温下的硬度，拉伸强度，冲击强度和压缩强度）进行了比较。已发现LPBF样品具有由初级树枝状菌落形成的细粒度柱状细胞微结构，并且由于结构缺陷（孔和孤立的微裂纹）而导致的机械性能较差。不同组成的Laves相（Cr ₂ Nb，Co ₂ Nb和Cr ₂Hf）在树突间空间中检测到。HIP有助于消除微裂纹，γ'相的沉淀（尺寸为0.5–7μm），Laves相的溶解以及MeC碳化物相的形成。这些事件的组合增加了合金的强度和延展性。固溶后不进行HIP进行时效处理会形成尺寸为150 nm至2μm的细粒度γ'相，消除了Laves相并沉淀了MeC碳化物（Cr ₂₃ C ₆），可以增强强度。但是，由于合金结构仍包含微裂纹，因此延展性仍然很低。经过组合后处理（HIP +溶液+时效处理）的LPBF样品由于消除了HIP时的结构缺陷并在溶液和时效过程中形成了细颗粒的γ/γ'微结构，因此具有最大的机械性能。