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 four-point 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 B4C-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 B4C-Ni composite showed flexural behaviour similar to that of an unreinforced Ni matrix. These results suggest that there was insufficient B4C 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·m0.5. Discontinuous, random cracks were observed on the B4C-Ni surface. The quantification of these properties is essential in evaluating the performance of the low-pressure cold sprayings to determine their potential applications.

This study evaluates the possibility of depositing hard B 4 C and TiC reinforcing particles in a Ni matrix using low-pressure cold spraying. It also investigates the effect of particle velocity and kinetic energy on deposition efficiency, microstructure, hardness, and wear resistance. B 4 C and TiC powders were blended at 50, 75, and 92 wt% carbide content with Ni powder comprising the remainder of the mixture. The impact velocity of sprayed carbide particles was calculated using a mathematical model based on the thermodynamics of compressible fluid flow through a converging-diverging nozzle. The model showed that the kinetic energy of TiC particles prior to impact was three times smaller than that of B 4 C, resulting in a higher carbide content (18 wt% compared to 8 wt%) due to reduced fracture and rebound of the TiC particles. Although the hardness values of both coatings are within the range of cold-sprayed WC-Co-Ni, wear rates were found to be high.

Typically, standard alloys do not have the wear resistance properties necessary to combat the aggressive wear and corrosive conditions prevalent throughout the oil sands mining process. For production-critical components, it is common to apply tungsten carbide-based metal matrix composite (WC-MMC) overlays to extend equipment life and prevent unplanned outages. The performance of composite overlays is very much dependent on the wear-environment. This paper will discuss how the interactions between abrasive conditions and the mechanical and structural properties of the WC-MMCs are key in determining the resultant levels of performance. Such information can lead to a better selection of materials and subsequent extended component life.

Minimizing wear of mining components in the oil sands industry is key to increasing productivity and decreasing excessive maintenance costs. A significant amount of research has gone into the selection of appropriate materials for improved wear protection. Tungsten carbide overlays are applied to the most critical components, typically by plasma transferred arc welding (PTA-W). This study aims at investigating the effects of several commercial PTA torches in terms of overlay microstructure and performance. A commercial tungsten carbide-NiCrBSi metal matrix composite (MMC) was used as the overlay material. A variety of parameters were studied when comparing the torches; including heat input, powder delivery, and deposition pattern. The effect of the overlay microstructure was examined using optical, digital and electron microscopy. The overlay performance was gaged using dry sand abrasion testing (ASTM G65-04). The type of torch, powder delivery method or power source did not have any significant effect on the quality or performance of the overlay in terms of microstructure or abrasion resistance.

Cold-gas dynamic spraying (“cold-spraying”) at low pressure (1034kPa/150 psig) was used to fabricate WC-Ni-Cu metal matrix composite (MMC) coatings. Tungsten carbide (WC)- based powder was mechanically blended with nickel (Ni) and copper (Cu) powder at various compositions. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Vickers micro-hardness testing were conducted on the cold-sprayed coatings. Image analysis was used to determine the WC content in the coatings. XRD profiles showed that no decarburization or oxidation of the WC reinforcing particles occurred in any of the coatings. The WC content in the coatings increased as the WC content in the powder increased, but did not increase further beyond 96 wt. % WC content in the powder blend. The results from Vickers micro-hardness testing confirmed that the coatings with the highest amount of WC had the highest hardness value. The coatings fabricated with a powder composition of 96 wt. % WC + 2 wt. % Ni + 2 wt. % Cu yielded a hardness of 385 ± 73 HV 0.3 /10 (n = 50). These results suggest that it is possible to use cold-spraying at low pressure to fabricate WC-based MMC coatings with improved hardness.

The processing of oil sand and heavy oil deposits is a highly aggressive environment. The combination of abrasive sands and corrosive media can lead to shortened and unpredictable component lives. A common method to try and extend the operational life of equipment is the application of tungsten carbide-based coatings by HVOF spraying. A number of commercial nanostructured coatings have been developed for this type of application. In this study, results will be presented that assess the effects of using a nanostructured tungsten carbide-based powder on the mechanical and wear-resistant properties of a HVOF-deposited coating.

Nowadays wire arc spraying of chromium steel has gained an important market share for corrosion and wear protection applications. In order to optimize the process parameters and to evaluate the effect of the spray parameters DoE based experiments have been carried out as well. In this paper, the effects of the process parameters of spray current, voltage and atomizing gas pressure on the particle jet properties of mean particle velocity and mean particle temperature as well as plume width are presented. To monitor these values the AccuraSpray system was used. The properties of the coatings with regard to morphology, composition and phase formation are included as well. These investigations are part of the development of new power supplies and the enhancement of spray parameter range. As a result of these experiments the spray parameters can be adjusted according to the requirements of the chromium steel coatings.