Microstructure and Performance of Ni/TiN Coatings Deposited by Laser Melting Deposition on 40Cr Substrates

The current study reports the successful preparation of Ni/TiN coatings via laser melting deposition (LMD) for repairing the shaft of an electric submersible pump (ESP). The surface morphology, microstructure, phase composition, microhardness, shear strength, and wear resistance were investigated using a scanning electron microscope (SEM), X-ray diffractometer (XRD), microhardness meter, shear strength test machine, and friction and wear tester. Among the three coatings, the Ni/TiN coating deposited at 1.5 kW processed fine grains with an evenly dispersed and compact structure. The Ni/TiN coating revealed a face-centered cubic (f c c) lattice that exhibited diverse orientations due to the laser powers. The Ni/TiN coating deposited at 1 kW had the lowest average microhardness of 768 HV, while the Ni/TiN coating deposited at 1.5 kW had the highest average hardness of 843 HV. The shear displacements of the Ni/TiN coatings obtained at 1, 1.5, and 2 kW were 0.68, 0.54, and 0.61 mm, respectively. The Ni/TiN coating deposited at 1.5 kW had the lowest friction coefficient among all coatings, with an average value of only 0.44. Additionally, the Ni/TiN coating deposited at 1.5 kW exhibited the highest wear resistance. The presence of Ni, Ti, N, Cr, and Fe elements on the surface of the shaft of the ESP, indicated that the LMD technology had successfully repaired the shaft.