Induction brazing of cermets to steel and eddy current testing of joint quality

The principal aim of the study was to demonstrate the feasibility of induction brazing of TiC-based cermets with Fe- and Ni-alloy binders under ambient atmosphere. A secondary aim was to investigate the possibility of using an innovative rapid non-destructive contactless testing method based on eddy current measurement for the evaluation of joint quality. Ag- and Cu-based filler metals and suitable fluxes developed for brazing of cemented carbides (WC-Co) to steels were employed. Results of the microstructure study and testing of shear strength enabled us to conclude that TiC-based cermets (TiC-FeCr and TiC-NiMo) can be successfully brazed under ambient atmosphere using filler metals and fluxes developed for WC-based cemented carbides. The shear strength of joints over 200 MPa can be achieved. Under similar brazing conditions, TiC-FeCr/steel joints compare favourably with TiC-NiMo/steel joints in terms of shear strength. The shear strength of TiC cermet/steel joints brazed with silver-based filler metal (Ag449) slightly increases (~13%) after prolonged heating at elevated temperature (250 °C).