Studies on the properties of high-velocity oxy-fuel thermal spray coatings for higher temperature applications
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SCIENCE FOR PRODUCTION STUDIES ON THE PROPERTIES OF HIGH-VELOCITY OXY–FUEL THERMAL SPRAY COATINGS FOR HIGHER TEMPERATURE APPLICATIONS T. S. Sidhu, S. Prakash, and R. D. Agrawal Materials operating at high temperatures in corrosive media suffer erosion-corrosion wear, oxidation, and hot corrosion. Among various methods used for the protection of the surfaces against degradation, we can especially mention the technology of application of coatings by high-velocity oxy-fuel spraying, which gives coatings which high strength and hardness, low (less than 1%) porosity, and high erosion-corrosion and wear resistances. The characteristics of the coatings and their protective properties are presented. The role of some high-velocity oxy-fuel coatings in the protection of metals and alloys against degradation at high temperatures in various media is demonstrated.
Protective Coatings In a wide variety of applications, materials have to operate under severe conditions such as erosion, corrosion and oxidation at higher temperatures in hostile chemical environments. Surface modification of these components is necessary to protect them against the indicated types of degradation [1]. Only composite materials are able to meet such a demanding spectrum of requirements: the base material provides the necessary mechanical strength and coatings provide a way of extending the limits of use of materials at the upper end of their performance capabilities by allowing the mechanical properties of the substrate materials to be maintained while protecting them against wear, erosion, or corrosion [2 – 3]. Even if the material withstands high temperatures without coating, coating enhances the life period of the material in this case. The main advantages of coatings are summarized as follows [4, 5]: — very high flexibility concerning alloy selection and optimization for specific resistance to corrosion environments and abrasion/erosion of particles; — surface properties can be separated from the required mechanical properties of the structural component; — coating systems (multi-layered or functionally graded) can be used by combining, e.g., good adhesion with optimized corrosion and erosion behavior; — unique alloys and microstructures can be obtained by thermal spraying which are not possible with wrought materials; these include continuously graded composites and corrosion-resistant amorphous phases; Metallurgical and Materials Engineering Department, Indian Institute of Technology Roorkee, Roorkee-247 667, India. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 6, pp. 80–95, November–December, 2005. Original article submitted February 19, 2005. 1068–820X/05/4106–0805
© 2005
Springer Science+Business Media, Inc.
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T. S. SIDHU, S. PRAKASH,
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R. D. AGRAWAL
— costs of the coating solution are normally significantly lower than those of highly alloyed bulk materials; thermal spray coatings are of especial interest due to their cost/performance ratio; — thermal-spray coatings additionally offer the possibility of on-
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