Effect of Pre-Oxidation on the Corrosion of TP347H Boiler Steel in 650℃ Water Vapor

Abstract

Supercritical power generation boilers often corrode in 650 °C water vapor. A study on chemical pre-oxidation protection of boiler steel surfaces was conducted to address this problem. Firstly, the TP347H boiler steel was placed in a tubular furnace with a flow rate of 20 mm/s of oxygen and oxidized for 2 h at 300 ℃. The protective effect of the oxide layer on the boiler steel was studied using the gravimetric method. Scanning electron microscope (SEM) was used to observe the surface morphology of the material. Combined with the product composition analysis, the following conclusions were obtained: after 2 h of oxidation at 300 ℃, the thickness of the oxidation layer of TP347H boiler steel could reach 0.2 μm. This oxide layer reduced the corrosion rate of the material in 650 ℃ water vapor by 87.5% compared to the material without pre-oxidation. The corrosion products of the TP347H boiler steel without oxidation after corroded in high temperature water vapor could be divided into two layers: the surface layer was mainly the oxide of Fe, and the bottom layer was the oxide of Fe, Cr, and Ni. The bonding strength between the two layers was poor, and the outer layer products were easy to fall off. After the surface oxidation treatment, the corrosion products of the sample were only a monolayer. The corrosion products were mainly oxides of Fe, Cr and Ni. The bonding strength between the coating and the substrate was good, and the corrosion products were not easy to fall off.

Keywords

• oxidation film|oxidation protection|generator set|boiler corrosion|tp347h boiler steel