Superhard nano WC-12%Co coating by cold spray deposition

Processing of cermet such as WC-Co is not easy by cold spray deposition, although cold spray process can eliminate the degradation of the WC phase as compared to conventional high velocity oxygen fuel (HVOF) or plasma spraying process. In this study, WC-12%Co powders with nano-sized WC were deposited by cold spray process using helium gas. Microstructural characterization and phase analysis of feedstock powders and as-deposited coatings were carried out by SEM and XRD. The results show, as expected, that there is no detrimental phase transformation and/or decarburization of WC by cold spray deposition. It is also observed that nano-sized WC in the feedstock powder is maintained in the cold sprayed coatings. It is demonstrated that it is possible to fabricate the nano-structured WC-Co coatings with low porosity and very high hardness (∼2050 HV) by cold spray deposition with reasonable powder preheating.