Numerical Simulation of Hot Isostatic Pressing Process Utilized During Sintering of Tool Inserts

Abstract

Sintering is a popular technique, where powder compacts are heated in a furnace to impart strength and integrity. Usually, sintering process is a one of the essential stage followed during powder metallurgy along with powder production and powder compaction. Sintering process is multistage and carried out in a partial vacuum with the controlled atmosphere to achieve required metallurgical properties. To make a product completely pore-free and dense, hot isostatic pressing (HIP), a secondary powder metallurgy operation is necessary. In hot isostatic pressing, argon gas is used as the pressure medium and isostatically applied to the sintered part with the pressure around 100 bar with a temperature range of 500–2000 °C. Although the hot isostatic pressing is a well-established technology, the understanding of local details like the internal gas flow and heat flux inside the furnace will help to improve the process itself as well as to reduce the rejection rate of the sintered inserts. In this paper, numerical simulation of hot isostatic pressing is presented. As the process involves unsteady flow through porous felt as well as graphite cylinders, transient analysis of argon flow inside the horizontal vacuum sintering furnace is simulated. The argon gas is passed into the furnace through an inlet at the mass flow rate of 300 L/h. The simulation is carried out for 1200 s with a time step of 0.01. Numerical results show the local temperature; pressure and flow conditions attained and eventually used for further process improvement particularly in the central zone of the furnace.