Effect of processing parameters on Tribo-mechanical properties of developed Nano-Composite Coating of h-BN & B4C on Ti6Al4V Substrate by Laser Surface Alloying

Abstract

ABSTRACT This work deals with the development of hard coating of h-BN + B4C mixed powder on the Ti6Al4V surface through laser cladding under different processing conditions of laser power and scanning speed. A hard multicomponent nanocomposite coating has constituent phases of TiB2-TiC-TiCN-h-BN-B4C-C3N4-B13C2. This composite coating has been synthesised by laser cladding of pre-placed h-BN and B4C mixed powders on the Ti6Al4V substrate. In this investigation, the average thickness of the coating has been taken up to 50 µm with a maximum microhardness of 2814 HV0.05. The developed coatings have been characterised by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy and hardness and wear test, and a correlation is established between the microstructure and the hardness value. TEM analysis reveals the formation of an intricate nanostructure in the coatings during laser cladding. The results indicate the significant improvement in the hardness and tribological characteristics of the coated Ti6Al4V substrate. Improvement in the hardness and wear resistance is attributed to the presence of nanocrystalline phases of C3N4, B13C2 and TiCN, which are formed due to the addition of titanium boride and titanium carbide elements. The present investigation provides valuable insights into the development of nanocomposite coating on the metal surfaces.