M. Yandouzi, B. Jodoin, University of Ottawa, Ottawa, ON, Canada; E. Sansoucy, University of Ottawa, OTTAWA, ON, Canada; L. Ajdelsztajn, University of California, Davis, Davis, CA
WC–Co cermets are well established as materials highly resistant to wear in a wide variety of situations; the main parameters influencing their properties are carbide grain size, their volume fraction and binder mean free path. Recent works have shown that nanostructured cermets offer improved properties over their conventional counterparts. Traditionally, these coatings are obtained using thermal spraying (TS) methods such as high-velocity oxy-fuel, plasma spraying, or detonation gun. However, due to the high temperature characteristics of the TS process, the WC–Co powder tends to undergo a combination of decarburization, grain growth, oxidation, and dissolution/reaction between the WC and Co during spraying. This behaviour results in the formation of hard and brittle phases (W2C, W, η-phases, WO3). Due to the limitations of current TS methods, the cold gas dynamic spray (CGDS) process performed at relatively low temperature provides an interesting and promising alternative.
The objective of this study is to successfully deposited WC-Co coating layers using continuous- and Pulsed- Cold Spray Process. Two types of feedstock powders, conventional and nanocrystalline were used. The analyses of both coated layers and feedstock powders were performed by different techniques (such as OM, XRD, SEM, TEM, EDS). The effects of deposition techniques on the microstructure of the coated materials have been evaluated. Compared to the continuous-cold spray process, the pulsed-one has shown to be a promising technique for the deposition of hard particles, in achieving extremely high particle velocity which required obtaining sufficient plastic deformation to produce a coating.
