LPBF and Post Processing of H13 Tool Steel

Abstract

Laser powder bed fusion (LPBF) is an innovative method where metal powder is fused together to generate complex geometries. LPBF is used as a technology to reduce material waste, and extensive labor that are often linked to conventional subtractive manufacturing. H13 tool steel is one of the widely used materials in several industries and has, therefore, gained interest in the additive manufacturing field due to its excellent mechanical properties. To produce H13 parts with optimal mechanical properties, printing parameters are optimized and a high relative density of 98% is obtained. Laser power of 203W, scanning speed of 700 mm/s, hatch spacing of 40μm and layer thickness of 25 μm are used to obtain the optimal results. Hot isostatic pressing is applied to cure the microcracks and has shown a 0.5% increase in the relative density, while it showed a significant decrease in other samples due to the excessive residual heat. Optical and scanning electron microscopy are used to observe the recrystallization of grains and grain growth resulted by tempering and rapid cooling. Tempering temperatures of 650˚C resulted in a greater reduction of microhardness than 550 ˚C. While high hot isostatic pressing temperature (1163 ˚C) shows a worsening effect on the microstructures