Additive manufacturing (AM) is an attractive manufacturing technology in tooling applications. It provides unique opportunities to manufacture tools with complex shapes, containing inner channels for conformal cooling. In this investigation, H13, a widely used tool steel, was manufactured using a laser powder bed fusion method. Microstructure, tensile mechanical properties, hardness, and porosity of the AM H13 after stress relieve (SR), standard hardening and tempering (SR + HT), and hot isostatic pressing (SR + HIP + HT) were investigated. It was found that the microstructure of directly solidified colonies of prior austenite, which is typical for AM, disappeared after austenitizing at the hardening heat treatment. In specimens SR + HT and SR + HIP + HT, a microstructure similar to the conventional but finer was observed. Electron microscopy showed that SR and SR + HT specimens contained lack of fusion, and spherical gas porosity, which resulted in remarkable scatter in the observed elongation to break values. Application of HIP resulted in the highest strength values, higher than those observed for conventional H13 heat treated in the same way. The conclusion is that HIP promotes reduction of porosity and lack of fusion defects and can be efficiently used to improve the mechanical properties of AM H13 tool steel.

增材制造（AM）是工具应用中的一种有吸引力的制造技术。它提供了制造具有复杂形状的工具的独特机会，这些工具包含用于共形冷却的内部通道。在这项研究中，H13是一种广泛使用的工具钢，是使用激光粉末床熔融法制造的。研究了应力消除（SR），标准淬火和回火（SR + HT）和热等静压（SR + HIP + HT）后AM H13的组织，拉伸力学性能，硬度和孔隙率。发现在硬化热处理中，在奥氏体化后，先前的奥氏体直接凝固的菌落的微观结构（AM的典型特征）消失了。在标本SR + HT和SR + HIP + HT中，观察到的显微组织与传统的相似，但更精细。电子显微镜显示，SR和SR + HT标本缺乏融合，并且球形气孔，这导致观察到的断裂伸长率出现了显着的分散。HIP的使用产生了最高的强度值，高于以相同方式热处理的常规H13所观察到的强度值。结论是，HIP促进了孔隙率的降低和熔合缺陷的缺乏，可以有效地用于改善AM H13工具钢的机械性能。