Microstructure and Wear Behavior of NbC-Reinforced Ni-Based Alloy Composite Coatings by Laser Cladding

Abstract

This work aims to evaluate the influence of laser power and reinforcement feeding rate on the microstructure, hardness, and wear behavior of NbC-reinforced Hastelloy C276^TM alloy composite coatings. From a dual feeding system, one-step metal-matrix composite coatings were deposited with 10, 30, and 50% mass feeding of NbC powder with laser powers of 1.5 and 3.0 kW. Coatings deposited with 1.5 kW and 30% NbC showed some degree of porosity due to a combination of NbC feeding rate and melting pool temperature. Laser power and NbC feeding rate altered the melting efficiency and substrate burn-in shape, remarkably influencing the dilution. The composite microstructure was comprised of Ni-γ (FCC) dendrites with interdendritic network carbide which, in turn, ranged from lamellar-like M₆C to blocky-like conjugated MC-M₂₃C₆ carbide. Primary petaloid-like MC [Nb] carbide was formed from a 30% reinforcement rate on, whilst a considerable number of unmelted particles was observed for 50%. The higher the reinforcement feeding rate, the higher the carbide fraction and better wear performance of low heat-input specimens. Synthesis with high heat-input sheds a light on the deleterious effect of the dilution and is not an option to enhance the wear performance.

Keywords
Metal-Matrix Composite; Nickel-based Superalloy; NbC Reinforcement; Microstructure; Wear