Hardfacing of thermite welded rail by flux-cored arc welding

Abstract

The surface defects on the service railway's thermite weld must be repaired. Repairing procedures of thermite weld surface defects should be cost-effective, safe, and easy in the field. Hardfacing is the most effective method for restoring thermite-welded rail head. Four conditions were investigated using two types of hardfacing alloys under different shielded gases during the FCAW process: single martensitic hardfaced layer with an austenitic buffer in self-shielded and Ar + CO2 mixed gas shielded conditions, and double-layered pearlitic hardfacing without a buffer in pure CO2-shielded and Ar + CO2 mixed gas shielded conditions. The microstructures of different conditions have been examined using both an optical microscope and a scanning electron microscope (SEM). The mechanical properties and wear behavior of hardfaced samples were evaluated using the micro-Vickers hardness test, the Charpy V notch impact test, and the ball-on-disc sliding wear test. The martensitic microstructure enhanced wear resistance, whereas the austenitic buffer layer improved impact toughness. In addition, hardness results revealed that the martensitic sample with the austenitic buffer layer was comparable to that of the original pearlitic rail and thermite weld. In terms of impact toughness, hardness, microstructure, and sliding wear behaviors, a martensitic electrode shielded by a mixed gas buffer layer performs best.