Comparative Study on the Microstructural and Mechanical Properties of WC-Co/AISI 1020 Steel Brazed Joint Obtained by TIG and Oxyacetylene Process

Abstract

In this work, the microstructural evolution and the mechanical properties of WC-Co / AISI 1020 steel brazed joint obtained by oxyacetylene and Tungsten Inert Gas (TIG) brazing process are investigated. The maximum peak temperature induced by TIG process and the introduction of a shielding gas cause a remarkable diffusion of Co and rearrangement of WC particles along the interface with the filler alloy. The Energy Dispersive Spectroscopy (EDS) analysis reveals that the inter-diffusion activity of elements across the interfaces especially Co and Ni is more important using TIG process compared to oxyacetylene process The mechanical behavior is carried out through micro-hardness measurements and toughness tests using Vickers Indentation fracture method on the WC-Co along the parallel line of the interface with the filler alloy. The results show that the brazed joint issued from TIG process becomes increasingly hard and brittle when approaching the WC-Co/braze interface and loses its toughness (7 MPa/m1/2 compared to 15 MPA/m1/2 for oxyacetylene process) with increasing the brazing temperature.