Microstructure and Mechanical Properties of 1.2709 Die Steel by Selective Laser Melting

Abstract

The differences of microstructure and mechanical properties of die steel (1.2709) prepared by selection of laser melting (SLM) process and traditional casting-forging process were studied. Sample A was prepared by SLM process. Sample B was prepared by mixing process (half volume using conventional casting—half volume of forging process application SLM). Sample C was prepared by traditional casting–forging process. Three sets of samples were subjected to the same process of solution treatment and aging treatment. The microstructures and mechanical properties of the three groups were studied. The results showed that the microstructure of sample A was a homogeneous and dense plate-like martensite structure, and they were different in phase distribution. The microstructure observation of sample B indicated that the part of the conventional casting-forging process consisted of martensite and carbide particles, but the SLM process consisted of a uniformly distributed elongated martensite structure. In the region of different forming process, there was a transition region with a width of 40 μm. The transition zone was relatively loose and the defects were relatively more. The microstructure of conventional casting–forging process 1.2709 die steel samples was mainly composed of lath martensite and carbide particles. In addition, the relative densities of the three sets of samples were close to 100%. The impact toughness values αKV, αKU and the impact absorbing energy KV2, KU2 of sample B, sample A and sample C showed an increasing trend, and the mechanical property difference was less than 15%. It is proved that the mechanical properties of 1.2709 die steel workpiece prepared by SLM process can meet the needs of engineering application.