Microstructure and Properties of Nickel-Clad Cubic Boron Nitride-Reinforced Ni-Based Composite Coating Laser Cladding on Martensitic Stainless Steel Substrates

Abstract

In this paper, nickel-clad cubic boron nitride (Ni/c-BN)-reinforced Ni-based composite coating was prepared on the martensitic stainless steel substrate by laser melting technology. The microstructure, phases and properties of the cladding layer were investigated by x-ray diffractometry, scanning electron microscopy, energy-dispersive spectrometry, microhardness test, wear test and potentio-dynamic polarization. The experimental results show that surface quality of the cladding was excellent and free of obvious defects when the Ni/c-BN content was 5 wt.%, while reticulation cracks appeared when the content was higher than 5 wt.%. In addition, compared with the coating without Ni/c-BN, the addition of Ni/c-BN made the coating form a new phase Ni₃B and a change in the eutectic tissue in the coating, which was made up of γ-Ni, Ni₃B and Ni₄B₃. After added Ni/c-BN, the hardness, wear resistance, and corrosion resistance of the coating increased first and then decreased. Excess Ni/c-BN reduced the solid solution B element content in the matrix and accelerates the formation of the crack of the coating, thereby deteriorating the hardness, wear resistance and corrosion resistance. The coating had the best hardness, wear resistance and corrosion resistance when the Ni/c-BN content was 5 wt.%.