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 prepared by laser cladding.
• With the addition of NiCrBSi, microstructure of the coatings presents the obvious difference.
• As the content of NiCrBSi rises, microhardness is increased while fracture toughness is reduced.
• As the content of NiCrBSi rises, wear morphology and wear mechanism present the regular change.
• The appropriate addition of Ni (21%) can contributes to improving wear resistance of the coating.

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, α(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 m1/2, 3.57 MPa m1/2, 3.02 MPa m1/2 and 2.92 MPa m1/2). 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.