The transient temperature field and microstructural evolution of additively manufactured AISI H13 steel supported by finite element analysis

Abstract

Laser powder bed fusion (L-PBF) is a process that directly fabricates objects in a layer-by-layer manner and is increasingly applied in industrial and academic activities because it can be used to rapidly develop complex parts. In this study, numerical modeling and experimental approaches were developed to study crucial parameters for consolidating AISI H13 tool steel processed by L-PBF. A finite element model is proposed to simulate the intricate transient temperature field generated by the heat of laser scanning along tracks and that from successive layers. The proposed model considers temperature-dependent properties and employs the absorptivity profile and anisotropically enhanced thermal conductivity to better estimate the melt pool dimensions, and the birth and death method is used to model the addition of new powder layers. Different laser powers and scanning speeds were employed to analyze the melt pool in the last layer, and a maximum error of 7% was calculated relative to the experimental results using a volumetric energy density of 183 J/mm3. Because of the heat accumulated by previous consolidation tracks, the temperature in subsequent tracks in the same layer increased, and a melt pool overlap of approximately 40% was observed for parameter combinations with low porosity. The thermal history provided by the numerical model was used to explain the presence of untempered martensite in the final processed layer and the periodic structure of quenched and partially tempered martensite in the inner layers.

Keywords

• Powder bed fusion
• Processing parameters
• Laser
• Thermal history
• Simulation