Publications and Presentations on HVAF and HVOF Coatings and Systems
This page contains a collection of scientific publications and technical presentations regarding HVAF, HVOF and thermal spray coating as a whole.
1.Kermetico Technical Presentation [PDF, 4MB] by Dr. Andrew Verstak.
An in-depth description of Kermetico HVAF features in comparison with conventional HVOF systems.
2. Qun Wang, Shiying Zhang, Yingliang Cheng, Jing Xiang, Xinqi Zhao, Guibin Yang Wear and corrosion performance of WC-10Co4Cr coatings deposited by different HVOF and HVAF spraying processes. [PDF, 3.7MB], 2012
This study compares three types of WC-10Co4Cr coatings deposited with high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) spraying processes. The experimental results indicated that the decarburization of the WC in the WC-10Co4Cr coating was dramatically influenced by the spraying equipment, and the non-WC phase content in the as-sprayed coatings greatly influenced their performances. The HVAF-sprayed WC-10Co-4Cr coating revealed the lowest degree of decarburization, achieving the best properties in terms of hardness, fracture toughness, abrasive and sliding wear as well as electrochemical corrosion resistance when compared to the two HVOF-sprayed WC-10Co-4Cr coatings.
3.Qun Wang, Zhaoxi Tang, and Limei Cha Cavitation and Sand Slurry Erosion Resistances of WC-10Co-4Cr Coatings [PDF, 3.7MB], 2015
Two WC-10Co-4Cr coatings were deposited by high-velocity oxygen fuel (HVOF) and high-velocity air fuel (HVAF) spray processes, respectively, and their basic mechanical properties, cavitation and sand slurry erosion resistances were investigated. The results show that the HVAF-sprayed WC-10Co-4Cr coating exhibited a lower degree of decarburization and better properties in terms of hardness, fracture toughness, porosity, cavitation and sand slurry erosion resistances than those of the HVOF-sprayed WC-10Co-4Cr coatings, respectively. Therefore, HVAF-sprayed WC-10Co-4Cr coatings may be better employed for the protection of hydro-turbine component surfaces against cavitation and sand slurry erosion.
4. R.K. Kumar, M. Kamaraj, S. Seetharamu, T. Pramod, and P. Sampathkumaran Effect of Spray Particle Velocity on Cavitation Erosion Resistance Characteristics of HVOF and HVAF Processed 86WC-10Co4Cr Hydro Turbine Coatings [PDF, 4.7MB] 2016
The hydro plants utilizing silt-laden water for power generation suffer from severe metal wastage due to particle-induced erosion and cavitation. High-velocity oxy-fuel process (HVOF)-based coatings are widely applied to improve the erosion life. The process parameters such as particle velocity, size, powder feed rate and temperature affect their mechanical properties. The high-velocity air fuel (HVAF) technology, with higher particle velocities and lower spray temperatures, gives dense and substantially nonoxidized coatings. In the present study, the cavitation resistance of 86WC-10Co4Cr-type HVOF coating processed at 680 m/s spray particle velocity was compared with HVAF coatings made at 895, 960, and 1,010 m/s. The properties such as porosity, hardness, indentation toughness, and cavitation resistance were investigated. The surface damage morphology has been analyzed by SEM. The cohesion between different layers has been examined qualitatively through scratch depth measurements across the cross section. The HVAF coatings have shown a lower porosity, higher hardness, and superior cavitation resistance. Delamination, extensive cracking of the matrix interface, and detachment of the WC grains were observed in the HVOF coating. The rate of metal loss is low in HVAF coatings implying that process parameters play a vital role in achieving improved cavitation resistance.
5. Gang Wang, Zhongjia Huang, Ping Xiao, Xiebing Zhu Spraying of Fe-based amorphous coating with high corrosion resistance by HVAF. [PDF, 2MB] 2016
Fe-based amorphous coating with the composition of Fe42.87Cr15.98Mo16.33C15.94B8.88 has been deposited on a mild steel substrate by high velocity air fuel thermal spraying. The microstructure and corrosion properties of the Fe-based alloy coating were studied in detail. It was found that the obtained Fe-based coating showed a fully amorphous state with about 100 µm in thickness. Also, the obtained coating exhibited very dense structure with a porosity of 1.5%. Polarization tests demonstrated that the coating exhibited better corrosion resistance than stainless steel in a NaOH solution and simulated seawater. The reasons for the superior corrosion resistance have been discussed from the alloy elements and the homogeneous structure of the Fe-based amorphous coating.
6. A. Verstak, R.K. Kumar Tungsten Carbide-Based HVAF Coatings for Protection of Petrochemical, Oil Drilling and Hydro-Power Equipment Against Wear and Cavitation [PDF, 10MB]
A presentation shows results of the Central Power Research Institute (CPRI), Bangalore, India, research of HVAF coating properties.
7. A. Verstak, G. Kusinski, High Velocity Air-Fuel Spraying and Its Applications in Oil and Gas Industry. [PDF, 435KB]
A study of HVAF coating application in oil and gas industry made together with a Chevron R&D specialist.
Kermetico HVAF and HVOF Thermal Spray Coating Equipment
Kermetico designs and manufactures three families of HVAF and HVOF thermal spray equipment:
- Convertible HVOF and HVAF equipment:
- Multifunctional HVAF AK systems, with the complete range of spray guns:
- AK7 – a high-power thermal spray system for spraying metals, alloys, and carbides onto large parts. Spray rate – 550+ g/minute (73+ lbs./hour);
- AK6 – a carbide gun to spray tungsten and chromium carbides with spray rate up to 466 g/min (63 lbs./hour)
- AK5 – a compact spray gun to effectively deposit coatings onto smaller parts and complex geometries. Maximum spray rate – 250 g/min. (33 lbs./hour).
- AK-ID – a gun to spray internal diameters 80 mm (3.15”) and larger
- AK-IDR– a rotating gun to spray bores 100 mm (4”) and larger and up to 600 mm (2’) deep. Maximum spray rate – 83 g/min (11 lbs./hour).
- AK-HH – a hand-held HVAF gun to spray manually on-site or on complex surfaces. Maximum spray rate – 250 g/min. (33 lbs./hour).
- Specialized HVAF S equipment:
- Additional equipment:
- A Grit Feeder for the grit blast preparation of parts to reduce overall set up and coating cost
- A Gas Permeability Tester for an instant qualitative check of a coating’s through porosity, now with Mass Flow
- A Powder De-Duster to screen fine particles from a metallic powder
Kermetico, Inc. – HVAF and HVOF Material Science Excellence, Equipment Manufacturing and Thermal Spray Coating Since 2006
We create equipment that helps material scientists, engineers, and business managers achieve and exceed their goals.
We have installed more than 130 Kermetico HVAF and HVOF systems in the USA, Canada, Europe, Japan, India, China, S Korea, Australia and even Namibia.
Many of our systems are at work in Universities and National Labs, but most of them are used in production thermal spray shops.
We proudly design and produce our thermal spray equipment in California and install it all over the world.
You can visit our R&D/coating center in Benicia, meet our team and see our HVAF and HVOF equipment in action.
We also provide HVAF and HVOF thermal spray coating services for customers here in the USA – directly and through our network of partners.
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