Quantification and Assessment of the Mechanical Strength of Low-Pressure Cold-Sprayed Tungsten Carbide-Nickel Metal Matrix Composite Coatings

A low-pressure cold spray system was utilised to fabricate tungsten carbide-nickel metal matrix composite coatings. Two types of feedstock powders were used based on different weight percentages of the carbide. A uni-axial tensile test was conducted on the as-sprayed coatings to investigate the effect of coating microstructure on the mechanical properties. The longitudinal strains were calculated using the digital image correlation technique and image analysis on scanning electron microscope micrographs to characterize the microstructure. The results showed a significant improvement in mechanical properties such as elastic modulus, ultimate tensile strength, and strain to failure with an increase in the carbide content in the coatings. This improvement was attributed to refined microstructural features with the decrease in the porosity of coating that was caused by significant consolidation of the matrix. Furthermore, this improvement was due to the increase in the interfacial area caused by the increase in carbide content, a decrease in average carbide size in the coating, and reduction in mean free path between the carbide particles. Thus, this correlation of the mechanical properties with the microstructure of the coatings suggests that cold-sprayed coatings with optimized microstructure may enhance the performance characteristics of these coatings.