The alloying effects of Cr on in-situ phase evolution and wear resistance of nickel composite coatings fabricated by wide-band laser deposition

In this work, nickel based composite coatings reinforced with WC and Cr particles were deposited by wide-band laser cladding. The alloying effects of Cr were investigated by microstructure characterization, phased identification, and property analysis such as microhardness and wear resistance. Results indicated the in-situ synthesized phases in laser pool mainly composed of gamma-Ni solid solution, (Cr,W)(5)B-3, (Cr,W)(7)C-3 and Cr23C6. Large quantity of block (Cr,W)(5)B-3 phases were synthesized as the Cr addition was blow 4 wt%. However, the coarse strip (Cr,W)(7)C-3 phase became the dominate precipitates as the Cr addition further increased. Statistics analysis of particle morphology showed that the (Cr,W)(5)B-3 phase was uniformly distributed block shape with median particle diameter D-50 = 8.97 mu m, while the (Cr,W)(7)C-3 phase was coarse strip shape with median diameter D-50 = 12.77 mu m. The average microhardness and wear resistance showed the best in coating 2# with 4 wt% Cr addition (873 +/- (HV)-H-85 and 1.8 x 10(-6) g/m respectively). Worn surfaces indicated the strip (Cr,W)(7)C-3 phases easily peeled off and thus decreased the wear resistance of composite coatings. The results in this work showed that the constitution and content of reinforced in-situ phases in nickel composite coatings could be modified by the alloying effects of Cr. As a result, the hardness and wear resistance were also improved with optimized Cr addition.