The structure and properties of hypervelocity oxy-fuel (HVOF) sprayed coatings

The structure and properties of HVOF sprayed WC-Co, CrC-NiCr, T-800 (Co-Mo-Cr-Si) coatings were investigated. The coatings were sprayed by three equipment manufacturers - Hobart Tafa Technologies, Plasma-Technik AG and Perkin-Elmer/Metco Division. The characteristics of the coatings were compared with those of identical coatings sprayed by plasma are spray. It was found that the HVOF coatings show better structural and mechanical properties as regards structure quality, bond strength, hardness and microhardness. The HVOF impact effect on the target material surface layer was determined. The WC-Co coatings are used as low-temperature erosion coatings. They are characterized by dense distribution of very fine WC particles, with very high microhardness (greater than or equal to 1050 HV300). The CrC-NiCr coatings are used as high-temperature erosion coatings. They are characterized by dense distribution of CrC particles and high microhardness (greater than or equal to 700 HV300). The T-800 is used as a low- and high-temperature wear coating. It is characterized by a solid solution structure and molybdenum base precipitates. The investigation shows that HVOF technology can lead to thicker and better coatings than those sprayed by plasma arc spraying.