Features of the impact of hot isostatic pressing and heat treatment on the structure and properties of maraging steel obtained by selective laser melting method

Abstract

Using the SLM method in a nitrogen blanket with heating to a temperature of 200 °C, samples were obtained at a position of 0° against the build plate. The effect of the hot isostatic pressing (HIP) and heat treatment (HT: hardening + aging) on the structure and mechanical properties of maraging steel CL50 WS was studied (the Russian analogue is ChS4 grade). To analyze the effect of post-processing on the strength characteristics (σb, σ0,2, δ, ψ), tensile tests were conducted. Their results indicated high values of strength and ductility. It has been established that as a result of HT in the steel structure, in addition to α-Fe, γ-Fe, dispersed precipitates of the NiTi3 strengthening phase are formed, the identification of which was carried out by high-resolution transmission electron microscopy. Through the NiTi3 intermetallic phase, the steel has acquired increased tensile strength and yield strength required for the production of critical components and parts for highly loaded turbomachine disks. The change in the porosity of the samples before and after the HIP was analyzed. The microstructure of the samples and the changes that occur under the influence of various post-processing options are studied. The fine-grained homogeneous structure obtained by combining the SLM, HIP and HT provided optimal strength and ductility. Analysis of fractures after mechanical testing showed that the samples after postprocessing are destroyed according to the viscous-pitting mechanism with the formation of a neck.