The effect of process parameters and characterization for the laser cladding of cBN based composite clad over the Ti6Al4V alloy

In the present study, a metal matrix composite of nitride, boride, and oxide layer over the Ti6Al4V substrate has been formed by using high-quality reinforcement like cBN, TiO2, and Ti6Al4V. Response surface methodology (RSM) has been successfully implemented to investigate the effect of process parameters (laser power, scanning speed, and shielding gas flow rate) on the responses like clad layer thickness and micro-hardness value of the cladded part. Statistical analysis shows that laser power and scanning speed significantly influence layer thickness and microhardness. Further considering the optimal combination of process parameters, cladded surfaces with different percentage compositions of reinforcement are characterized. The clad shows different microstructures like needles, cylindrical rods, and short-length dendritic. These confirm the formation of a metal matrix composites of nitrides and borides (TiN, TiAlN, AlN, and TiB2) as the main constructive phase of the clad. Further analyzing the binding energy of these phases through XPS, the formation of the compounds exhibits higher intensity. These enhance the hardness as well as wear resistance properties of the clad. The coefficient of friction in the cladded surfaces is less than the base material due to anti-wear chemical compounds like boride and nitride. However, spalling craters and wear debris are found in cladded samples.