某超临界机组过热器典型材质氧化皮化学清洗效果分析

Chemical cleaning effect of oxide scale on superheater tubes of a supercritical unit boiler

为了评价化学清洗治理过热器氧化皮技术的效果,采用失重法、能谱分析法和电镜显微观察金相组织等方法,对某超临界机组过热器3种典型材质T23,T91和TP347H氧化皮化学清洗前、后特性进行分析。结果表明:化学清洗可有效去除管材表面氧化皮,除垢率达90%以上;T23管材氧化皮主要为铁的氧化物,化学清洗可以完全去除;T91管材表面氧化皮分为2层,化学清洗后有部分内层氧化皮残留,残留部分为富铬层;TP347H管材清洗后氧化皮厚度明显减小,残余部分为富铬层;T91材质的耐腐蚀性能最差,腐蚀总量为18.97g/m2,腐蚀速率为0.38g/(m2·h),T23材质次之,TP347H材质耐腐蚀性能最好;化学清洗不会对奥氏体钢TP347H产生晶间腐蚀。

To evaluate the effect of chemical cleaning treatment on superheater oxide scale,three typical materials of a supercritical unit superheater,T23,T91 and TP347H,were analyzed before and after chemical cleaning.The corrosion situation,element content and microstructure of the oxide scales were tested by thermogravimetric analysis,energy spectrum analysis and metallographic analysis.The results show that,chemical cleaning can effectively remove the oxide scales on the surface of pipe sheets with removing efficiency over 90%.The oxide scales of T23 steel are mostly iron oxides,which can be totally washed and the metal base can be seen after chemical cleaning.The oxide scales of T91 steel consist of two layers,after chemical cleaning,there are some residues of the inner oxide layer,which is Cr-rich layer.The oxide scales of TP347 Hsteel pipes become thinner considerably after chemical cleaning,and the residue is Cr-rich layer.The T91 steel＇s anticorrosion performance is the worst,of which the total corrosion amount is18.97g/m^2 and the corrosion rate is 0.38g/（m^2·h）.Then is the T23 steel.The TP347 Hsteel performs the best.Chemical cleaning does not generate intergranular corrosion to austenic steel TP347 H.