4种先进超超临界电站锅炉用高温合金高温腐蚀性能实验研究

Experimental Study on High Temperature Resistance in Simulated Coal-ash Environment of Four Superalloys for AUSC Power Plant Boilers

目的研究Haynes 625、Haynes 617、Haynes 120和Inconel 740H四种先进超超临界电站锅炉用高温合金在高温模拟煤灰环境下的腐蚀行为及机理。方法利用XRD、SEM、EDS等分析手段对样品表面腐蚀产物进行微观分析。结果四种高温合金均具备一定的抗高温模拟煤灰腐蚀能力。未涂抹煤灰样品的腐蚀动力学遵循抛物线规律,说明所选高温合金在750℃的高温腐蚀行为主要受离子扩散控制。在涂抹模拟煤灰环境下,材料的氧化增重依次为:Haynes 617>Haynes 625>Inconel 740H>Haynes 120。Haynes 625与Haynes 617腐蚀产物为双层结构的氧化物,氧化内层主要为富Cr氧化膜,氧化外层主要成分为(Ni,Mn)Cr_2O_4;Inconel 740H与Haynes 120表面未见双层结构氧化物。结论氧化物结构与合金中铬元素含量有关,同时与合金中附加元素(如钴元素)的含量和行为有一定联系。四种高温合金抗高温腐蚀性能从大到小依次为:Haynes 120>Inconel 740H>Haynes 625>Haynes 617。与以往研究相比,并未发现腐蚀产物中存在S,表明腐蚀过程中腐蚀产物中的S来自于SO_2气氛,而非煤灰中的硫酸盐。

The work aims to study corrosion behavior and mechanism of four heat-resistant alloys for AUSC power plant boilers including Haynes 625, Haynes 617, Haynes 120 and Inconel 740 H in a simulated coal-ash environment at 750 ℃. The corrosion products on samples were characterized by means of XRD, SEM and EDS. Four superalloys exhibited certain resistance to high temperature simulated coal-ash corrosion. Corrosion kinetics of experimental materials without coal-ash followed a parabolic corrosion law, which indicated that high temperature corrosion behavior of the selected alloys at 750℃ was controlled by ion diffusion. Weight gain of materials in simulated coal-ash environment was as follows： Haynes 617 Haynes 625 Inconel 740 H Haynes 120. Corrosion products on the surface of Haynes 625 and Haynes 617 were oxides of bilayer structures. Internal oxidation layer was Cr-enriched film, while external oxidation layer mainly contained（Ni,Mn）Cr2O4. The bilayer structure was not found on the surface of Inconel 740 H and Haynes 120, which indicated that the oxide structure was related to chromium content, as well as content and behavior of additional elements including cobalt element. High temperature corrosion resistance of four superalloys was as follows： Haynes 120〉Inconel 740〉 H Haynes 625 〉Haynes 617. Compared with previous studies, S is not found in the corrosion products, which indicates that sulfides come from atmosphere of SO2 but not sulphate in coal ash.