火电机组锅炉受热面合金烟气腐蚀与应力协同作用失效行为研究进展

为响应国家提出的2030年碳达峰及2060年碳中和的目标, 火电发电机组蒸汽参数(如蒸汽温度与压力)尚需进一步提高, 这无疑为火电机组的安全运行带来严峻挑战。作为影响火电机组锅炉安全服役的两个重要因素, "高温烟气腐蚀"与"应力"协同作用导致锅炉受热面材料失效常被简化或独立研究。本文首先从烟气腐蚀和应力失效着手, 简述锅炉受热面合金烟气腐蚀机理, 分析影响烟气腐蚀性能的材料因素(金属种类、合金元素、金属表面状态)及环境因素(温度、腐蚀气氛及煤灰成分), 并从腐蚀与应力相互影响的角度, 讨论火电机组受热面合金在高温烟气腐蚀与应力协同作用下的失效行为。此类合金虽然在高温烟气腐蚀环境中不存在应力腐蚀开裂倾向, 但腐蚀产物会显著影响材料的高温蠕变及持久寿命。同时, 应力造成的缺陷会改变材料的腐蚀过程。因而, 本文重点介绍了火电机组锅炉环境下, 高温烟气腐蚀与应力协同作用对不同材料性能的影响, 并以18-8型奥氏体钢Super304H为例, 完整分析从烟气腐蚀行为到腐蚀与应力耦合作用行为。最后, 对未来烟气腐蚀与应力之间的相互作用及协同作用下材料的失效机理进行展望。

Research progress in failure behavior of alloys for hot-section components in thermal power plant boilers under synergism of fireside corrosion and stress

In response to the China's target of carbon peaking before 2030 and carbon neutralization before 2060, the steam parameters like steam temperature and pressure of thermal power generation need to be further increased to improve its thermal efficiency and reduce carbon emissions, which challenges the safety operation of thermal power plant. It is an important factor that the synergistic effect of high-temperature fireside corrosion and stress leads to the failure of alloys used for boiler, which is quite distinctive from the conventional stress corrosion cracking (SCC) since promising materials such as Ni-based superalloys are not sensitive to SCC tendency under the service condition of fireside corrosion coupled stress. Unfortunately, those impacts are often studied independently. The fireside corrosion mechanism and the stress failure of alloys were summarized in this paper, and the influential factors were pointed out from the materials (metal types, alloy elements and metal surface state) and the environments (temperature, corrosion atmosphere and coal-ash composition) that affect the corrosion performance of alloys. Furthermore, the failure mechanism of alloys from the perspective of the interaction between corrosion and stress was reviewed. On the one hand, the corrosion products deteriorate the creep rupture life of materials; additionally, the defects caused by stress will change the corrosion process of materials. Therefore, this paper focuses on the influence of the synergistic effect of high-temperature fireside corrosion and stress on the material performance, which is indicative for the design and performance of candidate materials for boiler environment of thermal power plants. As an example, the failure of Super304H under the fireside corrosion, creep and the synergism of fireside corrosion and stress were discussed. Finally, the prospect of future investigations on the interaction of fireside corrosion and stress was put forward, including the interaction between fireside corrosion and stress and the failure mechanism of materials under the synergistic effect.