Structure and stresses in high dimension brazed joints of cermets and steel

Purpose: of this paper is description of stresses in brazing joints of different physical and mechanical properties and evaluation of microstructure and mechanical properties of large dimensional vacuum brazed joints of WC–Co (ISO K05), Fe-TiC sinter plates (Ferro–Titanit Nicro 128) and precipitation hardened stainless steel of 14-5 PH (X5CrNiMoCuNb14-5) using copper as the brazing filler metal.Design/methodology/approach: Microscopic examinations with the use of scanning electron microscope were performed to establish microstructure of the joint. Shear strength Rt and tensile strength Rm of the joints have been defined.Findings: It have been state, that the basic factors decreasing strength of the joint, which can occur during vacuum brazing of the WC-Co, Fe-TiC sinters - Cu brazing filler metal - 14-5 PH steel joints are diffusive processes leading to exchange of the cermets and brazing filler metal elements. They can have an unfavourable influence on ductility and quality of the joint..Research limitations/implications: Results of numerical calculations of three-dimensional models of cermets and steel brazed joints stresses are presented. Particular attention was paid to stresses occurring in joints of large brazing surfaces. It was shown that joints microstructure and mechanical properties depend on chemical composition filler and parent materials, diffusion process during brazing, leading of the cermets and filler metal components replacement as well as joint gap thickness. The thickness of the joints and parent materials have an essential influence on the value of the local stress.Practical implications: As a result of conducted experiments criteria for generating high dimension coatings of cermets plates brazed to steel. The PM Fe-TiC and PM WC - Co composite plates vacuum-brazed to steel as cutting coatings have been worked out and applied in industry.Originality/value: An original value of the paper is to prove the tendency of concentration gradients of alloying components and intermetallic phases creation and factors reducing stresses which may occur during vacuum brazing of The PM Fe-TiC and PM WC-Co and corrosion resistance steel.