Low-pressure cold spray has been used as an innovative method to deposit metal matrix composite (MMC) coatings: boron carbide-nickel (B4C-Ni) and tungsten carbide-cobalt-nickel (WC-Co-Ni) composites. The coatings were studied using scanning electron microscopy, X-ray diffraction with Rietveld refinement, and acoustic emission-coupled fourpoint flexural test. Indentation fracture toughness tests were performed on the WC-Co-Ni coatings, only. The results showed that the composites had reinforcing particle volume fractions of 45.8 ± 0.3 vol. and 22.7 ± 0.1 vol. for the WC-Co-Ni and B_4C-Ni MMC coatings, respectively. Flexural tests were used to evaluate the fracture strain of the composites. In these tests, the WC-Co-Ni composite failed by brittle facture at approximately 0.5 nominal strain. The B_4C-Ni composite showed flexural behaviour similar to that of an unreinforced Ni matrix. These results suggest that there was insufficient B_4C within the coating to affect significantly the ductile failure mode of Ni matrix. Post bending fracture analysis showed the presence of straight, continuous cracks on the WC-Co-Ni surface and the indentation fracture toughness of WC-Co-Ni was found to be 1.2 ± 0.2 MPa·m~(0.5). Discontinuous, random cracks were observed on the B_4C-Ni surface. The quantification of these properties is essential in evaluating the performance of the low-pressure cold spray coatings to determine their potential applications.
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