Numerical simulation and optimization of WC-SS420 induction brazing process

Abstract

Tungsten carbide (WC) is a very hard, brittle, and relatively expensive cermet. It is often joined to more economical material, such as martensitic 420 stainless steel (SS420), to form a hybrid cutting tool stock. This article summarizes a study on the optimization of an induction brazing process joining these two materials using BAg-22 as filler metal. This study uses an integrated approach consisting of finite element analysis (FEA) modeling and experimental verifications. The thermal behaviors and the metallurgical transitions during the brazing cycles of WC-BAg22-SS420 joints are studied. This study investigated process and metallurgical issues due to mismatches in thermal expansion coefficient, thermal conductivity, and electromagnetic permeability. Using the optimum process parameters derived from simulation, joint strengths exceeding 370 AE 40 MPa for shear were obtained. The hardness of WC was unaffected by the brazing heat. However, softening in the SS420 next to the fusion interface was constantly observed in the experiments. The FEA modeling results demonstrated that using a controlled heating and cooling process schedule was effective in mitigating this softening phenomenon. Experimental verification of this mitigation method is currently under study.