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Long H.-G.,Hunan Xiangdian Boiler and Pressure Vessel Test Center Ltd | Long H.-G.,Hunan Electric Power Company | Xie G.-S.,Hunan Xiangdian Boiler and Pressure Vessel Test Center Ltd | Xie G.-S.,Hunan Electric Power Company | And 3 more authors.
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2013

Oxidation mechanism and characterization of steam-side oxidation scale formed on the internal surface of super-heater and re-heater tubes made of TP347H austenitic stainless steel removed from boiler of some power plant were investigated by metallurgic inspection, scanning electron microscope-energy dispersive X-ray (SEM-EDX) analysis and X-ray diffraction. The results show that the steam-side oxidation scale normally consists of three layers, the inner layer is heterosphere oxides layer consisting of (Cr, Fe)2O4 and NiO, the middle layer is loose and porous and identified as Fe3O4 with the coarse columnar crystal microstructure and the outer layer is compact but very thin and identified as Fe2O3 with the lower tine equiaxed crystal microstructure. Some fine equiaxed crystal oxides are observed in the interface of the inner and middle layers, which lowers the binding strength of the interface and the exfoliatation of scales more easier occurs. The flakes exfoliated from the steam-side oxidation scale of TP347H steel tubes are mainly made up of the outer layer and middle layer of the oxidation scale. Source


Xie G.,Hunan Xiangdian Boiler and Pressure Vessel Test Center Ltd | Xie G.,Hunan Electric Power Company | Long H.,Hunan Xiangdian Boiler and Pressure Vessel Test Center Ltd | Long H.,Hunan Electric Power Company | And 5 more authors.
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering | Year: 2013

Steam-side oxidation scales formed on inner surface of super-heater and re-heater tubes made of 10CrMo910 steel in a power plant were investigated by metallurgic inspection, scanning electron microscope-energy dispersive X-ray (SEM-EDX) spectrometer, and X-ray diffraction analysis. Results show that the steam-side oxidation scale normally consists of two layers: the inner layer is a heterogeneous oxidation film rich in Cr and pores, whereas the outer layer contains porous and fine particles identified as Fe3O4 and Fe2O3; internal oxidation exists at the interface between base metal and inner layer, resulting in compact bonding of the interface; the oxidation at interface between inner and outer layer is not obvious, where firm adhesion is formed and a small number of oxide particles are left after decomposition; both the inner and outer oxidation layer are composed of nanometer or micro particles, and the thermal stress caused by mismatch of thermal expansion coefficients are relaxed by pores lying in the oxidation particles. The steam-side oxidation film of 10CrMo910 steel tube is difficult to peel, and its growing thickness may cause the heating surface steel tube to work at overheating temperatures. Source

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