马氏体钢T91和奥氏体钢TP347H管材高温蒸汽氧化层特性研究

Characteristics of Oxide Scales Formed on T91 Martensite Steel and TP347H Austenite Steel in High Temperature Steam

对含异种管材(T91马氏体钢和TP347H奥氏体钢)的末级过热器的蒸汽氧化层进行研究。借助X射线衍射仪、金相显微镜、含能谱的扫描电镜等手段,对比分析氧化层生长和剥离的特征和规律。结果表明:T91、TP347H管材蒸汽氧化层差异显著;以Fe2O3的出现和含量作为管材氧化层剥离行为的征兆,并不具有通用性;T91管材氧化层容易产生孔洞或微裂纹,诱发剥离行为;TP347H管材容易形成连续完整的富铬保护带,减缓氧化层生长。

The oxide scales formed in high temperature steam on dissimilar materials,i.e.T91 martensite steel and TP347H austenitic steel,in the final superheater of a 350 MW supercritical generation unit were characterized by means of X-ray diffraction,metallographic microscope and scanning electron microscope with energy spectrum,with emphasis on the growth and spallation of oxide scales.The results indicated that there were significant differences of the oxide scales formed on T91 and TP347H tubes.It was not absolutely reasonable to adopt the emerge and the quantity of the formed Fe2O3 as the critical index for prediction of oxide scale spallation.Furthermore,the oxide scale on T91 tube often contains voids and/or microcracks,which can obviously induce the oxide scale spallation.However,for TP347H tube a continuous and compact inner oxide scale rich in chromia forms at the interface of oxide scale/substrate,which may act as an effective barrier to the growth of oxide scale.