Hot corrosion behavior of Ni−xCr−6.8Al based alloys
(1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. State Key Laboratory of Porous Metals Materials, Northwest Institute for Nonferrous Metal Research,
Xi’an 710016, China)
2. State Key Laboratory of Porous Metals Materials, Northwest Institute for Nonferrous Metal Research,
Xi’an 710016, China)
Abstract: The hot corrosion behaviors of as-cast and preoxidized Ni−xCr−6.8Al based alloys in the mixture of Na2SO4+25%NaCl at 873 K were studied. The results show that the mass loss of Ni−xCr−6.8Al based alloys decreases with the increase of Cr content. Preoxidation improves the resistance to corrosion regardless of the concentration of Cr. The kinetics of as-cast Ni−12Cr−6.8Al and Ni−16Cr−6.8Al based alloys fits the parabolic law well, while that of the as-cast Ni−20Cr−6.8Al based alloy fits the power law. The kinetics of all the preoxidized samples obey the logarithmic law. The mechanism of the as-cast alloys can be well explained by the acid-base melting model. The behavior of the preoxidized alloys is found to be mainly determined by the properties of the oxide layer formed during the preoxidation to a large extend.
Key words: Ni-Cr-Al based alloy; hot corrosion; Cr content; preoxidation; kinetics; corrosion mechanism