Microstructure and properties of metal parts remanufactured by laser cladding TiC and TiB2 reinforced Fe-based coatings

Abstract

Laser cladding process, an efficient surface remanufacturing method, has become a research hotspot in recent years. Herein, in situ titanium carbide (TiC) and titanium diboride (TiB2) reinforced composite coatings were fabricated on the surface of damaged carbon steel to improve the hardness and wear resistance of remanufactured parts. Effects of addition of 5B4C and 15Ti (in wt.%) powder on morphology, phase composition, microstructure, and mechanical properties of specimens were comprehensively investigated. Results revealed that milled groove could be effectively filled with composite coating, which formed good metallurgical bonding with the substrate. Furthermore, sequentially precipitated in situ synthesized phases including TiC, TiB2, Cr3C2, Fe2B, and Fe3C in composite coating could continuously increase nucleation sites and further refine grains. Moreover, uniformly distributed reinforcements effectively weakened the directivity of heat flow during solidification process and promoted columnar to equiaxed transition. Mechanical properties illustrate that micro-hardness of composite coating with 961.94 HV0.3 is 4.14 and 5.04 times, and corresponding volume loss is 7.8 and 2.8 less than those of 316 L coating and standard 45 steel, respectively. This study indicates that in situ formed ceramics reinforced composite coating can act as an ideal candidate for remanufacturing damaged parts, and further improve their wear resistance.