Hot Corrosion Behavior of Stainless Steel with Al-Si/Al-Si-Cr Coating

Abstract

The 1Cr18Ni9Ti stainless steel with Al-Si/Al-Si-Cr coatings is prepared by slurry process and vacuum diffusion, and the hot corrosion behavior of the stainless steel with/without the coatings is studied under the condition of Na2SO4 film at 950 °C in air. Results show that the corrosion kinetics of stainless steel, the stainless steel with Al-Si coating and the stainless steel with Al-Si-Cr coating follow parabolic laws in several segments. After 24 h corrosion, the sequence of the mass gain for the three alloys is the stainless steel with Al-Si-Cr coating < the stainless steel with Al-Si coating < the stainless steel without any coating. The corrosion products of the three alloys are layered. Thereinto, the corrosion products of stainless steel without coating are divided into two layers, where the outside layer contains a composite of Fe2O3 and FeO, and the inner layer is Cr2O3. The corrosion products of the stainless steel with Al-Si coating are also divided into two layers, of which the outside layer mainly consists of Cr2O3, and the inner layer is mainly SiO2. The corrosion film of the stainless steel with Al-Si-Cr coating is thin and dense, which combines well with substrate. Thereinto, the outside layer is mainly Cr2O3, and the inside layer is Al2O3. In the matrix of all of the three alloys, there exist small amount of sulfides. Continuous and protective films of Cr2O3, SiO2 and Al2O3 form on the surface of the stainless steel with Al-Si and Al-Si-Cr coatings, which prevent further oxidation or sulfide corrosion of matrix metals, and this is the main reason for the much smaller mass gain of the two alloys than that of the stainless steel without any coatings in the 24 h hot corrosion process.

Si-Al-N-O Multi-Layer Coatings with Increased Corrosion Resistance Deposited on Stainless Steel by Magnetron Sputtering

“…Such layers have proven themselves in aggressive media at high temperatures, because aluminium oxide has outstanding mechanical properties and high chemical stability at high temperatures. Silicon oxide [15,37,38] in addition to chemical stability has high hardness and strength.…”

Understanding the Role of a Cr Transition Layer in the Hot-Salt Corrosion Behavior of an AlSi Alloy Coating

“…Furthermore, the Si doping accelerated the selective oxidation of Al to generate an Al 2 O 3 protective layer. Unfortunately, during high-temperature corrosion exposure, the AlSi coatings suffered from significant elemental inter-diffusion [24][25][26][27][28][29][30]. According to the literature, the upward diffusion of Fe caused the creation of the (Fe 2 Al 5 + FeAl) alloy phase, which resulted in significant volume shrinkage and coating cracking.…”

“…According to the literature, the upward diffusion of Fe caused the creation of the (Fe 2 Al 5 + FeAl) alloy phase, which resulted in significant volume shrinkage and coating cracking. These microcracks served as the diffusion pathways for the combined salt, speeding up the interaction between the developing Cl 2 and Al, resulting in significant coating deterioration and mass loss [28,29].…”

Damping Behavior of Layered Aluminium and Aluminide Coatings on AISI 316 Austenitic Steel

“…Of all coatings, thermal barrier coatings (TBCs) have the most complex structure and can even operate in the most demanding high-temperature environments. TBCs, which comprise metal, intermetallic, ceramic and multilayers, insulate turbine and combustor engine components from the hot gas stream and improve the durability and the time-life in exercise [1][2][3][4][5].…”

“…(1) As aluminized by a 5 min hot-dipping ( Figure 1a), having an inner intermetallic layer and an outer Al-Si alloy layer, 200 µm thick. (2) As aluminized by a 3 min hot-dipping ( Figure 1b), having an inner intermetallic layer and an outer Al-Si alloy layer, 130 µm thick. (3) As aluminized by hot-dipping and successively oxidized in furnace at 900 • C for 1 h (Figure 1c).…”