Improvement of the High-Temperature Erosion-Corrosion Resistance of Incoloy 800 by Cladding of 25.35.4CNB Reinforced by SiC

Abstract

The objective of this study is to improve the high-temperature erosion-corrosion resistance Incoloy 800 for the application used as thermowell at 900°C. In weld cladding procedure, silicon carbide (SiC) particles were pre-deposited on the Incoloy 800 substrate, followed by the cladding of Ni-base alloy filler (34Ni-25Cr-0.4C-Ti-W-Mo) by a gas tungsten arc welding. A theoretical amount of SiC particles mixed with filler was 2 - 30%wt. A particle size of SiC was in the range of 50-150 mm. The results showed that the addition of 15%wt SiC led to the maximum hardness of the cladding layer. Addition of particles more than 15wt% tended to provoke cracks in cladding layer. The larger particle size exhibited the higher hardness. An erosion rate of cladding surface was further tested by the perpendicular impingement of 1-mm SiC abrasion sands on the sample surface with air flow velocity of 220 m s-1 at 900°C in air. For cladding layer with the same amount of SiC mixed, the one mixed with larger particle size exhibited the higher erosion-corrosion resistance. Likewise, for cladding layer mixed by the same size of SiC, the addition of particle with a smaller amount promoted the higher erosion-corrosion resistance. The addition of 2.6 wt% SiC particles with 150 mm size in cladding layer showed the surface with the best erosion-corrosion resistance in this study. No oxide scale was, however, observed on eroded surface due to the spallation by high impact erodent particles.