Abstract
Due to their mechanical properties, WC-based cermet coatings are extensively used in industrial wear-resistant applications. These coatings are usually prepared using thermal spray processes. However, due to the nature/environment of the spraying processes, the feedstock powder structure and properties suffer from severe decomposition, which subsequently degrade the performance of the coatings produced. The cold spray process appears to be a promising process alternative to preserve the properties of the feedstock powder during the coating preparation. Although, the later technique can eliminate or minimize the degradation of the material, the deposition of cermet is a complex process. In this study, nanocrystalline WC-15Co and conventional WC- 10Co4Cr coatings were deposited using both the continuous and the pulsed cold spray processes. Microstructures of the feedstock powders and the coated layers were investigated by OM, SEM and XRD. The results revealed the possibility of depositing cermet coatings onto aluminum substrates by both processes without any degradation of the phase composition of the feedstock powder. However, the continuous process experienced difficulty in depositing and building up dense coatings without major defects. Meanwhile, the new pulsed process revealed the capacity of depositing thick cermet (conventional and nanocrystalline) coatings with low porosity as long as the feedstock powder was preheated above 573 K.
