Performance of 75Cr3C2-25NiCr Coating Produced by HVOF Process in a Coal-Fired Thermal Power Plant

Abstract

In the present investigation, 75Cr3C2-25NiCr coating was deposited on T91 boiler tube steel substrate by high velocity oxy-fuel (HVOF) process to enhance high-temperature corrosion resistance. High-temperature performance of bare, as well as HVOF-coated steel specimens was evaluated for 1500 h under cyclic conditions in the platen superheater zone coal-fired boiler, where the temperature was around 900 °C. Experiments were carried out for 15 cycles each of 100 h duration followed by 1 h cooling at ambient temperature. The performance of the bare and coated specimens was assessed via metal thickness loss corresponding to the corrosion scale formation and the depth of internal corrosion attack. The uncoated boiler steel suffered from a catastrophic degradation in the form of internal oxidation attack and thickness loss. The 75Cr3C2-25NiCr coating showed good adherence to the boiler steel during the exposures with no tendency for internal oxidation.