| Coal-fired power generation takes the largest proportion in Chinese power supply.As the increase of China's requirements for energy conversion efficiency and environmental protection,it is necessary to adopt advanced ultra-supercritical power generation technology.But as the temperature increases,matals in boiler are more likely to get corrupted,which may influence the safety and the efficiency of generating units seriously.So it's necessary to do research on the corrosion resistance of USC unit boiler material.This article focused on Chinese 'AD-700 Project'.Experimented Incone1740H,Haynes282 and Inconel617B in steam at 650 ?,700 ? and 750 ? for 200h,400h,600h,800h,1000h,1500h and 2000h.Measured weight gain of the samples,observed the micro structure of oxide and analysised the element distribution in the oxide layers after experiments.Results showed that these three Ni-based alloys are all relatively preservative.Weight gain data:Inconel740H<Inconel617B<Haynes282.For Incone1740H,the microstructure of oxide caused by 750 ?-steam differs from that caused by steam below 700 ?.Microstructure of oxide on Inconel617B changes when steam tempreture changes.Microstructure of oxide on Haynes282 usually divides into two kind of areas by the shape of oxides.Analyzed the influence of temperature,chromium content and dissolved oxygen on oxidation behavior.If a Ni-based alloy contains enough Cr to form a Cr-rich oxide layer,the Cr-rich oxide layer will prevent the diffusion of metal ions,reduce the oxidation reaction rate.When the temperature increases,metal oxidizes faster,the oxide layer becomes thicker and the oxide surface gets more rough.In higher tempreture,it is more likely for Cr-rich oxide to turn into volatile compounds,which has a negative effect on oxide stability.An increase on the amount of dissolved oxygen will lead to a higher partial pressure of oxygen on the oxide layer and the environment interface,which will make oxidize faster and weight gain larger. |
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