摘要
采用等离子粉末熔覆工艺方法,选用Ni-Cr基合金粉末在TP304H奥氏体不锈钢表面进行了Ni-Cr合金涂层的制备,对合金涂层的微观组织、相结构及成分进行了分析,研究了不同温度(650℃和750℃)对Ni-Cr合金涂层在模拟锅炉燃烧环境中腐蚀行为的影响。结果表明:Ni-Cr合金涂层与基体之间为冶金结合,合金涂层组织均匀,呈枝晶生长特征,涂层主要由Fe0.64Ni0.36和Ni-Cr-Fe相组成;Ni-Cr涂层在烟灰/气环境中腐蚀的主要原因为碱金属硫酸盐溶解加速作用和烟气中O、S与熔覆层形成的易挥发性腐蚀产物;腐蚀温度对材料耐蚀性影响尤为重要,随温度的升高Ni-Cr合金涂层的耐蚀性明显减弱,750℃高温腐蚀500 h后,腐蚀产物厚度约为650℃的2倍,腐蚀产物层出现严重的破裂、脱落现象,并伴随大量的晶间腐蚀;腐蚀产物层成分主要为富Fe、Cr氧化物,另有少量硫化物,且硫化物的含量随温度的升高明显增加。
The Ni-Cr based coating was prepared on surface of the TP304H stainless steel by the plasma powder cladding technology. The microstructure, phase and chemical composition of the coating were analyzed. The influence of temperature on corrosion behavior of the Ni-Cr coating was also investigated in simulated coal combustion environment at 650 ℃ and 750 ℃, respectively. The results show that, the Ni-Cr coating was metallurgically bonded to the substrate and the microstructure of the coating is uniform. The coating prepared was mainly consisted of Fe0.6aNi0.36 and Ni-Cr-Fe. The corrosion of the Ni-Cr based coating in coal ash/gas environment was mainly caused by the accelerating effect of alkali metal sulfate dissolution and volatile corrosion products formed by O, S and cladding in the flue gas. The effect of corrosion temperature on corrosion resistance of the materials was particularly important. The corrosion resistance of the Ni-Cr coating decreased significantly with the increasing temperature. After corrosion for 500 h, the thickness of the corrosion products at 700 ℃ was twice thicker than that at 650 ℃. Obvious intercrystalline corrosion and spallation of corrosion products occurred at 700 ℃. The XRD results indicate that, rich Fe and Cr oxides in were the main corrosion products for all of the samples, while the mount of sulfides increased obviously with the exposed temperature.
出处
《热力发电》
CAS
北大核心
2017年第4期70-76,共7页
Thermal Power Generation
基金
国家自然科学基金项目(51301130
51401163)
中国华能集团公司总部科技项目(HNKJ15-H02
HNKJ15-H04)~~
关键词
Ni-Cr涂层
等离子熔覆
煤灰腐蚀
温度
TP304H
耐蚀性
晶间腐蚀
氧化膜
Ni-Cr coating, plasma cladding, coal ash corrosion, temperature, TP304H, corrosion resistance, intergranular corrosion, oxide film
