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

Abstract

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 γ-Ni solid solution, (Cr,W)5B3, (Cr,W)7C3 and Cr23C6. Large quantity of block (Cr,W)5B3 phases were synthesized as the Cr addition was blow 4 wt%. However, the coarse strip (Cr,W)7C3 phase became the dominate precipitates as the Cr addition further increased. Statistics analysis of particle morphology showed that the (Cr,W)5B3 phase was uniformly distributed block shape with median particle diameter D50 = 8.97 μm, while the (Cr,W)7C3 phase was coarse strip shape with median diameter D50 = 12.77 μm. The average microhardness and wear resistance showed the best in coating 2# with 4 wt% Cr addition (873±85HV and 1.8 × 10−6 g/m respectively). Worn surfaces indicated the strip (Cr,W)7C3 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.