Abstract
In this study, nanostructured WC-Co coatings were produced using experimental nanocrystalline WC-12Co and WC-24Co powders produced by a novel chemical synthesis route. Test coatings were produced using HVAF spraying keeping the temperature as low as possible during the deposition in order to avoid decomposition of the nanocarbides. In experimental powders, two different Co incorporation methods were used: a conventional way in which cobalt was incorporated as a metallic Co powder and a chemical synthesis way in which cobalt acetate was used as a cobalt source. When using cobalt acetate, it decomposes to metallic cobalt during the process. Experimental powders in which cobalt acetate has been used as cobalt source resulted poor deposition efficiency. With warmer parameters, powders resulted better DE, but significant WC decarburization and the dissolution into the matrix phase occurred. Powders in which Co has been introduced as Co powder showed enhanced DE enabling spraying with decreased temperature and higher particle velocity, resulting in coatings with less WC decomposition. Especially, an experimental powder in which Co has been incorporated both as Co powder and as Co-Ac results very fine nanocarbide structure with significantly less WC decomposition having a hardness value of 1201 HV0.3, even with 24% Co.
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Acknowledgment
The authors would like to thank the Academy of Finland for financial support (NANOSOLU project, Decision Number: 266496). In addition, authors would like to thank Thermal Spray Center Finland and Mr Ville Matikainen and Mr Mikko Kylmälahti for co-operation in HVAF spraying. Authors give their thanks to Ms Hanna-Mari Sinilehto for participating to experimental work and characterization.
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This article is an invited paper selected from presentations at the 2017 International Thermal Spray Conference, held June 7-9, 2017, in Düsseldorf, Germany, that has been expanded from the original presentation.
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Karhu, M., Lagerbom, J., Kaunisto, K. et al. Nanocrystalline WC-Co HVAF Coatings by Utilizing Novel Powder Manufacturing Route Using Water-Soluble Raw Materials. J Therm Spray Tech 27, 196–206 (2018). https://doi.org/10.1007/s11666-017-0668-9
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DOI: https://doi.org/10.1007/s11666-017-0668-9