Three body abrasive wear of X12CrNiMo martensitic stainless steel laser alloyed with TiC

Abstract

Martensitic stainless steels (MSSs) are often used for applications that require high wear resistance and hardness. A laser multi-track overlapping process was employed to fabricate TiC-reinforced metal matrix composite (MMC) coatings on X12CrNiMo steel substrate using a 4.4 kW continuous wave (CW) Nd: YAG laser. 50 and 75% overlap were produced. Comparative studies of the three-body abrasive wear resistance of the MMCs and the native material were carried out. The composite microstructures consist of homogeneous distribution of TiC grains and were free from cracks. Significant improvement in the hardness and wear resistance properties were obtained in the alloyed samples compared with the as-received MSS. The 75% overlap MMC has lower porosity, higher hardness and superior abrasive wear resistance than the 50% overlap. Key words: Laser alloying, microstructure, abrasive wear, porosity. INTRODUCTION Wear is a surface phenomenon and is primarily determined by the surface properties of a material rather than by the bulk properties. In this respect, surface modification techniques offer a solution to the problem of wear. Among the various techniques, laser alloying is especially attractive because of its unique features of process control (Candel et al., 2010). Laser alloying is enjoying increasing interest in many centres in the world. This type of surface treatment is used for improvement of hardness and abrasion wear resistance by influencing the structure change, mostly by introduction of powder particles into matrix on the material surface. Laser alloying is characterised by violent mixing of constituents in the melt pool, solidification of the remelted materials, convection motions in the laser melt pool which decides the final distribution of the alloying element in the remelted zone and a big temperature gradient. The powder is either introduced directly by the nozzle during alloying, or else