The effect of microstructure on abrasive wear of hardfacing alloys

Hardfacing is one of the most useful and economical ways to improve the performance of components submitted to severe wear conditions. A study was made to compare the microstructure and abrasion resistance of hardfacing alloys reinforced with primary chromium carbides, complex carbides or tungsten carbides. The hardfacing alloys were deposited onto ASTM A36 carbon steel plates by a shielded metal arc welding (SMAW) method. Three different commercial hardfacing electrodes were employed to investigate the effect of the microstructure. The abrasion tests were carried out in a dry sand-rubber wheel abrasion machine according to the procedure A of ASTM G65 standard. Microstructure characterization and surface analysis were made using optical and scanning electron microscopy. The results showed that the wear resistance is determined by the size, shape, distribution and chemical composition of the carbides, as well as by the matrix microstructure. The best abrasion resistance was obtained in microstructures composed of eutectic matrix and primary M7C3 or MC carbides, while the higher mass losses were measured in completely eutectic deposits. The main wear mechanisms observed at the surfaces included micro-cutting of the matrix and brittle fracture of the carbides.