Microstructure and wear behaviour of a vanadium carbide reinforced weld coating

High resistivity against hard abrasive wear conditions can be obtained by coating the bulk low cost base material with high performance tool steel coating. In this study, thick wear resistant coatings of vanadium carbide reinforced tool steel were manufactured with conventional PTA-welding technique. Two different coated test piece configurations were prepared for wear tests and microstructure characterization work. The coatings were heat treated in temperatures at or well over the austenizing temperature of the steel base material used. The state of the coating materials was characterized with hardness measurements, cross-sectional microstructure studies with scanning electron microscopy and also with X-ray diffraction measurements. Abrasive wear resistance of the heat treated coatings was evaluated with a modified ASTM G65 rubber wheel abrasion wear tests and impact resistance at very severe wear conditions was tested with special impact wear tests. Heat treating after the welding procedure is seen to remove the retained austenite very effectively from the coating material structure and to produce very fine detailed precipitate structure besides more coarse V4C3 carbides in the coating material. Abrasive wear resistance of the tested coating material was found to be low against hard silicon oxide particles used in the tests. This is mainly because of the small carbide size and also the low volume fraction of these carbides reinforcing the coating material against abrasive wear. Heat treatment over 950 °C was hardening the coating and therefore impact wear resistance of the coating was found to be reducing when higher heat treating temperatures were utilized. This was because the particles were fracturing off the sharp test piece edge during the test.