Tribological effects of boriding treatment on a low carbon steel repaired by wire and arc additive manufacturing

Recently, electric arc-based welding processes have gained significant attention in the manufacturing sector due to their usefulness for repairing or remanufacturing damaged mechanical components. The changes in microstructure and mechanical properties of materials and components repaired by electric arc-based welding techniques have been the focus of most of current research. Since most of components are damaged by wear during operation, the improvement of such repaired/welded materials or components in terms of tribological properties for each specific application is wanted. In this work, the effects of applying a thermochemical treatment (boriding) as a tribological booster on a low carbon steel repaired by arc welding were studied. The tribological behavior (coefficient of friction (CoF) and wear volume) of the repaired steel before and after being borided was evaluated by means of micro-abrasion tests to replicate three-body abrasion under muddy environments. In addition, the physical and mechanical characteristics of the boride coating in both the original material and the repaired zone were evaluated by optical microscopy, X-ray diffraction, instrumented hardness tests and the VDI adhesion test. The wear scars were analyzed by scanning electron microscopy (SEM) and non-contact profilometry to identify the resulting wear mechanisms and to measure wear scars, respectively. The results showed that boriding treatment was effective to increase the hardness and wear resistance of the repaired low carbon steel without creating gradients of hardness, CoF, wear resistance or adhesion strength between the surface of the original material and the repaired zone.