Dissimilar joining of cemented carbide to low-carbon steel via combustion welding: Effect of process parameters on the interfacial microstructure and joint strength

Abstract

An innovative method based on pressure-assisted combustion synthesis reactions in compressed powder mixtures of nickel and titanium was developed to join WC-Co cemented carbide to VCN-150 steel (Standard No. 1.6582). A specially-designed experimental setup was used for induction heating of the samples under uniaxial pressure in an argon atmosphere. Rapid heating of the samples provoked the exothermic reaction between Ni and Ti, resulting in the in-situ formation of an NiTi-based intermediate layer between the steel and carbide parts. XRD and SEM-EDS analyses as well as shear strength test were used to characterize the samples and evaluate the quality of the joint. XRD analysis showed NiTi as the main phase in the joining layer. It was found out that a decrease in Ni particle size led to an increase in the contact surfaces of the powders and intensity of the reaction, resulting in improved adhesion of the joining parts, decreased porosity within the interlayer, and increase in the average shear strength. Although increasing the thickness of the bonding layer resulted in more intensive reactions, higher liberated heat, and wider diffusion layers at the interface, it led to relatively weak joints due to a rise in the volume percentage of porosity. The most favorable results in welding were obtained by using fine particles of the reactants and minimum thickness of the green interlayer (2 mm). By increasing the applied force during the process to ~600 N, shear strengths up to ~77 MPa could be obtained.