核电蒸发器用690耐蚀合金常采用冷轧方式成型, 其退火和时效处理后的晶粒度和碳化物分布与形貌需要采用适当的试剂侵蚀后进行统计分析。常用的10%草酸溶液(质量分数)侵蚀剂不适用于冷轧管材晶粒度分析, 而腐蚀性强、难以保存的2%溴-甲醇溶液(体积分数)难以适应批量管材碳化物形貌分析需求。甄选腐蚀性低, 易于储存且能有效显示690合金管材显微组织的金相侵蚀剂成为其金相试样制备过程中的重要组成部分。采用光学显微镜和扫描电镜分析了不同金相侵蚀剂显示的退火态和时效态690耐蚀合金管材的奥氏体晶粒和碳化物形貌, 从而选择出最佳侵蚀剂。结果表明: 采用2 g高锰酸钾+11 mL硫酸+90 mL去离子水溶液化学侵蚀可优先显示奥氏体晶界, 便于统计分析退火态690合金管材的晶粒度和晶粒尺寸分布;采用80%磷酸溶液(体积分数)和4%硝酸酒精溶液(体积分数)双重电解侵蚀可替代强腐蚀性的2%溴-甲醇溶液, 能够有效显示时效态690合金管材中的碳化物分布与形貌。

The 690 corrosion resistant alloy tubing for nuclear power evaporator is usually produced by cold rolling. The analysis of grain size and carbide distribution and morphology are required after annealing and aging treatment using certain etchants. In practice, 10% (mass fraction) oxalic acid solution seems not to be satisfied for analyzing grain size of cold-rolled tubing. And corrosive 2% (volume fraction) Br-ethanol solution is not satisfied for the carbide analysis during industrial manufacturing because it is volatile and difficult to store. The selection of new etchants for microstructure characterization is important during the manufacturing of 690 alloy tubing. Effects of etchants on grain size and carbide morphology were investigated by optical microscopy (OM) and scanning electron microscopy (SEM) for annealing and aging 690 alloy tubing. The results show that the solution of 2 g KMnO4+11 mL H2SO4+90 mL H2O solution attacked the austenite grain boundaries firstly and was convenient for statistic analyzing of the grain size and grain size distribution of annealing 690 alloy tubing. The dual electro-etching method using 80% (volume fraction) H3PO4 solution and 4% (volume fraction) HNO3 ethanol solution could be a substitute for the corrosive 2% Br-methonal solution and was effective for revealing the carbide morphology and distribution of aging 690 alloy tubing.