Effect of NiCrBSi content on microstructural evolution, cracking susceptibility and wear behaviors of laser cladding WC/Ni-NiCrBSi composite coatings

Ni-based composite coatings were produced on the Ti6Al4V substrate by laser cladding 30 wt.% WC/ 70 wt.% (Ni-NiCrBSi). The microstructural evolution and mechanical properties were investigated in details. The results indicated that the coating (70 wt.% Ni) was mainly composed of WC and TiC as reinforcements, alpha(Ti), TiNi and Ti2Ni as the matrix. Two new phases (W, Ti) C and Ni3B were formed in the coating (21 wt.% Ni-49 wt.% NiCrBSi). When the content of NiCrBSi was further increased to 63 wt.% and 70 wt.%, the matrix was transformed into TiNi and TiNi3, and microstructural uniformity was also improved. As the contents of NiCrBSi were varied (0 wt.%, 49 wt.%, 63 wt.%, 70 wt.%), the average microhardness of the coatings was increased gradually (745 HV0.1, 976 HV0.1, 1046 HV0.1 and 1107 HV0.1), however fracture toughness presents the opposite change trend (4.20 MPa m(1/2), 3.57 MPa m(1/2), 3.02 MPa m(1/2) and 2.92 MPa m(1/2)). Wear mechanism was also changed from the micro-cutting into the mixture of the micro-cutting and the brittle debonding, into the brittle debonding. The appropriate addition of Ni (21 wt.%) into the 30 wt.% WC-NiCrBSi cladding material was favorable to the improvement in wear resistance of the coating. (C) 2014 Elsevier B.V. All rights reserved.