Microwave joining of SS-316 plates: A multi-physics simulation study

Abstract

Microwave hybrid heating has emerged as a new technique for joining metallic materials. The presence of a multi-material system (bulk and powder) and the selection of suitable interface powder in microwave joining offer challenges. The present work addresses these issues for microwave joining of SS-316L plates using different interface powders nickel-based (EWAC 1004 EN) and SS-316L interface powders. A multi-physics model of the microwave joining setup was developed to theoretically study the joining characteristics of SS-316L joints using both powders at 2.45 GHz and 900 W. The SS-316L joints were developed experimentally in 720 s and 680 s while using interface powders EWAC and SS-316L, respectively. The model was validated with experimental results and simulation was performed to analyse the electric field distribution, resistive losses, temperature distribution, thermal stress distributions, and energy utilization. The simulation results showed that the electric field intensity was 4.96 % higher in EWAC-based joint as compared to SS-316L-based joint; consequently, the EWAC-based joint attained a temperature of 1450 °C at the central plane. The resistive loss was found maximum between the susceptor and joint interlayer in both joints. Thermal stress was 62 % higher in EWAC-based joint than SS-316L-based joint. Microstructural investigation of the joints revealed that EWAC-based joints contained columnar and dendritic grain structures; while equiaxed grains were present in SS-316L-based joints. Porosity and grain size were higher by 34 % and 53 %, respectively in EWAC-based joint than SS-316L-based joint.