Effect of Laser Power on the Microstructure and Corrosion Resistance of NiCrBSi(Nb) Laser Clad Coatings

Abstract

Aiming to enhance the surface properties of low-carbon steel, NiCrBSi coatings containing 10 wt.% Nb were fabricated via pulsed laser cladding. Samples were realized with laser power ranging from 2800 to 3200 W. Scanning electron microscopy (SEM), coupled with energy-dispersive X-ray (EDX) analysis, was used to examine the microstructure and chemical composition. X-ray diffraction (XRD) was employed to evaluate the new phases formed within the coatings compared to the initial powder composition. Hardness measurements and corrosion resistance in a 3.5% NaCl solution were conducted to evaluate the effect of the Nb alloying on the properties of the cladded layers. In all cases, good metallurgical bonds were formed between the coatings and the substrate. However, the coatings produced at low laser power were thinner, and the substrate experienced more intense thermal exposure, resulting in increased dissolution of iron from the substrate. Increasing the laser power significantly enhanced the hardness of the coating compared to coatings produced using lower power. These phenomena can be the result of improved powder cladding efficiency, which can lead to thicker coatings with enhanced corrosion resistance. The results suggest that Nb addition can lead to improved mechanical behavior and corrosion resistance, but the process is highly dependent on the parameters and mainly on the laser power.