Abstract
In this study, thermo-mechanical simulation was conducted to predict thermal and stress behavior in Selective Laser Melting (SLM). Temperature-dependent material properties for processed material 304L stainless steel were incorporated into the model in order to capture the change from powder to fully dense solid stainless steel. Temperature and thermal stress history were tracked under conditions of different parameter sets which were designed to reduce defect formation. The thermal model predicted the temperature history for multi-track scans under different process parameters, such as laser power, effective scanning speed and hatch spacing. Subsequently, the corresponding melt-pool size, solidification rate and temperature gradients could be calculated from simulated temperature data. These three parameters from the simulation were compared with experimental melt pool size, grain structure and cell spacing data obtained from a Renishaw AM250. The experimental data were also used to determine unknown simulation parameters required by the continuum model, e.g., the optical penetration depth and thermal conductivity multiplier for the molten region. This allowed the simulation model to accurately predict melt pool size and solidification structure of SLM 304L stainless steel. Simulated stress showed that the subsequent thermal cyclic melting in successive scanned tracks resulted in alternating compressive and tensile thermal stresses. This work will provide insight for studying microstructure morphology, residual stress and deformations in the SLM process of 304L stainless steel.
Highlights
Selective Laser Melting (SLM) is a powder bed-based Additive Manufacturing (AM)technology
The focus of this paper is to investigate the microstructure and thermal stress history, which are controlled by the thermal history and solidification parameters, of stainless steel 304L in the SLM process
The used process parameters, laser power, hatch are spacing and scan speeds, The 304L stainless steel samplessuch with as different dimensions displayed in Figure are listed in Table
Summary
Selective Laser Melting (SLM) is a powder bed-based Additive Manufacturing (AM)technology. In order to produce parts with engineered properties, it is critical to understand SLM process parameters affecting thermal behavior and microstructure, such as laser spot size, power, scanning speed and scanning strategy. It is time-consuming and costly to analyze through experiments the effects of different process parameters on the temperature distribution, solidification behavior and mechanical properties of parts. This problem can be solved with recourse to numerical models, which have shown advantages for understanding the relationship of process parameters to thermal history and ultimate mechanical properties
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