High performance of Al‐Si‐CVD‐FBR coating on P92 steel against steam oxidation at 650 °C: Part 1

Abstract

Thermogravimetric analysis (TGA) and mass spectrometry (MS) of initial steam oxidation at 650 °C in Ar + 40% H2O for 150 h of the P92 steel with and without aluminum‐silicon‐CVD coating were investigated. We deposited Al‐Si coating on ferritic/martensitic (F/M) P92 steel using the chemical vapor deposition in a fluidized bed reactor (CVD‐FBR) at 580 °C for 2 h and subsequently heat‐treated in Ar at 700 °C for 2 h. The thermodynamic software Thermo‐Calc was used for theoretical simulations in equilibrium under similar experimental oxidation conditions from 500 to 900 °C. TGA verified that the P92 steel coated with Al‐Si had not gained weight compared to the uncoated oxidized P92 steel that gained 5.25 mg/cm2. The coated sample, with protective oxide layers, i.e., silica (SiO2) and alumina (Al2O3) on the diffusion zone, was better protected during steam oxidation. Al‐Si‐CVD‐FBR coating helped to delay catastrophic oxidation and avoid loss of chromium from steel through volatilization. SEM: EBSD/EDAX and XRD were used to study morphology/composition and structure of the samples.