Influence of post-treatment on the performance of SLM forming 18ni300 electroplated coatings

Hot isostatic pressing (HIP) is widely used to enhance the intrinsic properties of additively manufactured 18Ni300 martensitic aging steel, which can eliminate internal defects and optimize the microstructure of additively manufactured metals. However, there is still a lack of systematic knowledge about the influence of hot isostatic pressing on the interfacial properties of chromium plating on its surface, which makes it difficult to provide a reliable theoretical basis and process guidance for the precise optimization of plating properties under complex working conditions. In order to solve the above needs and technical problems, this paper centers on the post-treatment strengthening effect of chromium plating on the surface of additively manufactured 18Ni300 alloy to carry out in-depth investigation. Without post-treatment of pure chromium plating layer flatness and roughness degradation phenomenon obviously exists, through the XRD analysis to confirm that the composition of its physical phase contains Fe-Ni phase, FeNiCr phase and monolithic Cr residual phase. The microstructure response of chromium plating layer after heat treatment shows complex characteristics, transverse crack network and delamination phenomenon is triggered by the internal stress relaxation and crystal structure reconstruction of the plating layer. 600℃/70MPa hot isostatic pressing conditions, the plating layer surface flatness and interfacial straightness can be maintained, but there are still many internal pores, and densification needs to be improved. 1150℃/150MPa hot isostatic pressing process has a significant effect on the optimization of the performance of the layer: the surface flatness and interface straightening can be maintained, and the internal porosity still has more holes, and densification should be improved. The optimization effect is obvious: the surface flatness is well maintained; the interface with the substrate is formed; the hardness is greatly increased to 406.3-673.1HV0.2 ± 10%, and the monolithic phase disappears completely. The effective modulation of the atomic diffusion behavior at the plating-substrate interface by the hot isostatic pressing treatment was confirmed by the study: metallurgical bonding was strengthened; crack formation was suppressed; and the hardness and corrosion resistance were significantly improved. The results of the study open up an important new technological path for the optimization of surface protective layers of additively manufactured alloys.