HVOF two layer coatings consisting of Diamalloy 2002 (top layer) and 4010 (bottom layer) onto carbon steel sheets are carried. The microstructure and chemical composition of the resulting coatings are examined using the Scanning Electron Microcopy (SEM) and Energy Dispersive Spectroscopy (EDS). The indentation tests are carried out to evaluate the microhardness and surface elastic modules of the resulting coatings. It is found that the coating produced for Diamalloy 2002 results in higher hardness and elastic modules than that corresponding to Diamalloy 4010.

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Purpose -The purpose of this paper is to investigate the corrosion resistance of high velocity oxy-fuel (HVOF)-sprayed Diamalloy 2002 coating on carbon steel. The coating microstructure is examined in line with the corrosion resistance. Design/methodology/approach -HVOF spraying of coating is achieved, and the coating response to electrolytic solution is measured experimentally in terms of corrosion resistance. Findings -HVOF coating improves the corrosion resistance of the substrate such that the corrosion rate of the substrate is 7.1 mpy and the coating results in 4.5 mpy. However, presence of deep pit sites at the surface suggests the occurrence of preferential corrosion around the splat boundaries. In addition, closely spaced surface texture peaks act as crevice corrosion centers at the surface while initiating the formation of deep pit sites. Research limitations/implications -This study is limited by experimental investigations. In future, it may be extended to include model studies.Practical implications -The findings of this study are very useful for those working in the coating industry. However, HVOF coating is limited to high temperature protection in harsh environments. Social implications -It is useful for the power industry, particularly for gas turbines. Originality/value -It is an original work and describes the corrosion resistance of the coating surface. It is found that the coating improved the corrosion resistance of the steel surface.

In the present study, two layer HVOF coatings of carbon steel is carried out. The microstructural changes in the coating layers and fracture toughness of the coated surface are examined. The micro indentation method is incorporated for the fracture toughness measurements, while optical and scanning electron microscopy are used for the microstructural analysis. It is found that the fracture toughness of the coating surface produced by the tungsten carbide blended powders is less than that of the coating produced by corrosion resistance powders. Key words: HVOF, Diamalloy 2002, Diamalloy 4010, Fracture toughness.