Characterization of Particle Size Effects on Sintering Shrinkage and Porosity in Stainless Steel Metal Injection Molding Using Multi-Physics Simulation.

In this study, three stainless steel materials (17-4PH, 316L, and 304) were experimentally simulated using metal injection molding (MIM) technology to explore the size shrinkage behavior and defect formation mechanism of materials with different particle sizes during sintering. The sintering environment was linearly heated to 1250 °C at a rate of 5 °C/min and kept warm for 90 min. Multi-physics field coupling analysis was performed using ANSYS Workbench software. Two different regions were selected to simulate the total deformation trend of the material during sintering. The simulation results were compared with data from SEM and EDS analyses to elucidate the influence of particle size on shrinkage behavior and defect distribution. The findings indicate that the gaps between particles far away from the gate position became larger, the degree of densification decreased, the porosity was higher, and the number of white dot inclusions increased. Among the three materials, 17-4PH, which had the smallest particle size, had a greater sintering driving force, a better degree of densification, a smaller predicted total deformation, and a higher shrinkage rate, which is consistent with the hardness test data and the actual density data. In addition, the densification advantage of small particle size powder is not only related to surface energy but is also closely linked to the uniformity of its microstructure. The analysis in this study further promotes the performance optimization of stainless steel materials, indicates a scientific basis for future process improvements and high-precision parts manufacturing in MIM technology, and points to the development direction for high-performance materials.