An Overview of Characterisations and High Temperature Behaviour of Thermal Spray NiCr Coatings
N. Bala, H. Singh, S. Prakash
International Journal of Materials Science
Abstract
Advances in materials development and cooling schemes have led to increased operation temperatures of gas turbines, boilers and industrial waste incinerators. The combination of such high temperatures with contaminants of the environment and low grade fuels, such a sodium, sulphur, vanadium and chlorine, require special attention to the phenomenon of hot corrosion. There is an increasing interest in the deposition of Ni based metallic alloys by thermal spray methods like HVOF, Detonation and Pla...Moresma Spray for protection against corrosion in the above areas. Ni based coatings are used in applications where oxidation or hot corrosion resistance is required. In the studies reported on the Ni 50%Cr alloy coating sprayed by the detonation method, it was observed that this coating performed well in an actual refuse Incineration Plant. This plant operated for about seven years without any problems and the coated tubes were still expected to have a longer life. The significance of biofuels and other chlorine - containing fuels in electricity and steam production is growing rapidly. Biomass waste and high chlorine coals are reported to cause severe materials wastage in combustors. In another reported study, a synthetic atmosphere simulating biofuel combustion was created to test various coatings and it was observed that Ni50Cr HVOF coating performed well and no corrosion products were detected from the coating. In another research, it has been reported that HVOF Ni20Cr coating showed the lowest value of porosity and provided highest resistance under corrosive environments of Na2SO4- 60% V2O5 at 9000C . Results obtained from various studies proved that NiCr based alloys can perform well in reducing as well as oxidizing chlorine containing environments. This paper outlines the characterization of NiCr plasma spray coatings and gives a review of the applications of the same for corrosion/ erosion-corrosion under different types of environments.
keywords:NiCr; High temperature oxidation; Hot corrosion; Plasma spray; HVOF
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