Microstructure and Dry Sliding Wear Behavior of Laser Cladding (TiC+TiN)-NiCrWC Powder Composite Coating on DZ125 Superalloy

Abstract

Ni-based TiN-TiC composite coating was fabricated on DZ125 superalloy surface by laser cladding. The phase constitution and microstructures were investigated by means of X-ray diffraction (XRD), optical microscope (OM) and scanning electron microscope (SEM). Microhardness measurements and wear experiments without lubrication were also accomplished. The experimental results showed that a pore- and crack-free coating with metallurgical bonding to the substrate was obtained. Solidification morphologies along the section of the coating varied from directional dendrite in the interface to random dendrite in the surface. The coating was mainly composed of γ-Ni, M23C6, TiN, TiC particles and a small amount of NiTi, respectively. The average microhardness of 705HK for the coating was 2.3 times higher than that of the substrate. Wear tests indicated that wear resistance of the coating was significantly improved compared with that of the substrate. The improvement in hardness and wear resistance was attributed to TiN and TiC phase and chromium carbide uniformly dispersed in the matrix of the Ni-based TiN-TiC composite coating.