Effect of platinum and pre-oxidation on the hot corrosion behavior of aluminide coating with NaCl at 1050 °C

Abstract

The hot corrosion behaviors of the aluminide coatings with different treatments on the surface of Ni-based alloy at high temperature were investigated. The aluminide coating modified by three different methods (pretreatment, Pt-modification and both), and then all the specimens were oxidized in lab air with NaCl salt at 1050 °C. During cycle oxidation, oxide scales on the surface of the aluminide coatings presented different morphologies, composition and corrosion behaviors. The oxide scale on the surface of the as-received aluminide coating without any treatments showed a poor dense and a bad adherence. However, the oxide scale on the surface of the aluminide coating with both Pt-modification and pre-oxidation exhibited the best hot corrosion resistance. In the NaCl corrosion environment, different treatments resulted in different corrosion mechanisms. Without any treatments, the oxide scale with NaCl at high temperature occurred internal active oxidation, which could promote the corrosion process and form the pores in the oxide scale. The internal active oxidation also presented in the oxide scale on the surface of the aluminide coating with pre-oxidation.

Effect of Pre-Oxidation on High-Temperature Oxidation Behavior of Al-Si Coating on Nickel-Based Superalloy

“…In recent years, through studying the influence of pre-oxidation on the high-temperature oxidation and heat resistance corrosion properties of the coating, Yang [ 9 ] found that a Pt-Al-coated sample can form a continuous and dense Al 2 O 3 film after pre-oxidation treatment, which can effectively prevent molten salt from directly entering the material surface, and the pre-oxidized samples did not indicate internal oxidation or a vulcanization phenomenon. In the process of a hot corrosion experiment, the oxide film formed on the surface of the pre-oxidized Al-Si coating is thin and maintains good integrity, but the structure of the oxide film formed fluctuates greatly, indicating that the oxide film grows toward the inner layer of the coating during the process of oxidation dissolution [ 10 , 11 ]. Gao Bo et al [ 12 ] studied the influence of oxidation on the high-temperature oxidation and hot corrosion behavior of Co-Al-W-based superalloy and found that, when the alloy pre-oxidized at 950 °C under normal oxygen, partial pressure was oxidized at 1000 °C, the oxidation products fell off less, the oxidation mass gain was slowed down and the oxidation resistance of the alloy was improved.…”