Optimal gating system design for investment casting of 17-4PH stainless steel enclosed impeller by numerical simulation and experimental verification

The impellers of centrifugal pumps are highly susceptible to the latent damage of corrosion and cavitation after long periods of transporting chemical fluids. To enhance the structural integrity and effective lifespan of impellers, this study applied mold flow analysis to the design of gating systems for 17-4PH stainless steel enclosed impellers. Our objective was to eliminate shrinkage and porous defects common in investment casting. We adopted various bottom, side, and top pouring systems with different pouring parameters to examine the behavior of the molten metal flow and solidification in the mold cavity. We designed a pressurized gating system with specific gating ratio to achieve a stable flow velocity at in-gates. Physical sensors preset in the interior of the cavity were also used to detect thermodynamic behavior and analyze phase changes during casting simulations. The probability of shrinkage defect formation was assessed using the retained melt modulus (RMM) and the Niyama criterion. Experiments and nondestructive inspections show that optimizing the design of the gating system prevented surface shrinkage and interior defects. The improvements also reduced post-processing time and costs, increased yields, and enhanced casting quality.