低压等离子喷涂MCrAlY涂层的高温耐腐蚀性能

High temperature corrosion resistance of MCrAlY coatings deposited by low pressure plasma spraying

针对燃气轮机高温透平叶片在Na、V、S环境的高温熔盐热腐蚀问题,采用低压等离子喷涂NiCoCrAlTaY和CoNiCrAlY涂层,通过组织结构分析和腐蚀试验,对比分析了两种涂层与IN 738高温合金的高温抗熔盐腐蚀性能。结果表明:低压等离子喷涂过程中两种涂层材料的氧化程度较弱。预氧化形成的致密连续的热生长氧化物(TGO)膜可延缓涂层发生腐蚀。随着腐蚀时间延长,预氧化形成的α-Al_2O_3被消耗,并逐渐产生Cr-Ni与Co-Ni等尖晶石氧化物以及硫化物。700℃腐蚀环境中两种涂层的腐蚀速率约为基体的1/10,900℃时约1/7,且NiCoCrAlTaY涂层的抗熔盐腐蚀性能略优于CoNiCrAlY涂层。

Aiming to the high temperature corrosion occurred in turbine blades of gas turbine engines with fuel containing Na, V and S elements, NiCoCrAlTaY and CoNiCrAlY coatings on IN 718 superalloy were prepared by using low pressure plasma spraying deposit technique. The high temperature corrosion behaviors of these two coatings and IN 738 supperalloy were compared and analyzed. The results show that both coatings exhibit less oxidized during spraying. Dense and continuous thermally grown oxide （TGO） film which formed during pro-oxidation treatment can slow down the corrosion rates of the coatings. With the extension of corrosion time in high temperature environment, α-Al2O3 is consumed and Cr（Co）-Ni spinels and sulfides form gradually. The corrosion rates of both coatings in 700 ℃ and 900 ℃ are about 1/10 and 1/7 of IN 738 superalloy, respectively. Moreover, the resistance against high temperature molten salt corrosion of NiCoCrAlTaY coating is slightly higher than that of CoNiCrAlY.