The Microstructure and Properties of Laser-Cladded Ni-Based Self-Fluxing Alloy Coatings Reinforced by TiC Particles

In this study, NiCrBSi composite coatings reinforced with 5–15 wt.% TiC particles were prepared using laser cladding to investigate the influence of the TiC content and laser beam power on the coatings’ quality, structure, and properties. Penetrant tests revealed the presence of cracks in the composite coatings, which were reduced with the higher laser power due to a decrease in cooling rate. A macroscopic analysis showed that pure NiCrBSi coatings exhibited a high quality and were free of defects, while the addition of TiC particles led to the formation of large pores, particularly in coatings produced with a lower laser power. Microstructural characterization was conducted using Scanning Electron Microscopy (SEM), Energy-Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD). The microstructure of the pure NiCrBSi coatings consisted of an austenitic matrix with chromium-based precipitates (carbides and borides). Variations in structural morphology across different regions of the coatings and under varying laser powers were described. When TiC particles were added, partial dissolution occurred in the molten pool, enriching it with titanium and carbon, which subsequently led to the precipitation of titanium carbides. The average microhardness of the composite coatings increased by 28%–40% compared to the pure NiCrBSi coating, while the erosion resistance remained comparable. Solid particle erosion tests in accordance with the ASTM G76-18 standard resulted in average erosion values of the pure NiCrBSi coating of 0.0056 and 0.0025 mm3/g for the 30° and 90° impingement angles, respectively.