碳含量对Cr25Ni20型奥氏体耐热钢高温氧化性能的影响

对两种不同碳含量的Cr25Ni20型奥氏体耐热不锈钢分别加热到800 和1 100 ℃循环氧化96 h后,进行了循环氧化分析,并利用扫描电镜观察钢材表面氧化膜形貌;利用X射线衍射仪对氧化膜进行物相分析;采用划痕法测量氧化膜与金属基体的黏附力。结果表明,氧化膜是由菱形结构的Cr2O3晶粒和尖晶石结构的MnCr2O4晶粒组成,随着氧化温度的升高,氧化物晶粒变得粗大并由菱形结构向尖晶石结构转变;碳含量的增加造成“贫铬”现象的发生,减缓保护性氧化膜的生成,降低氧化膜与金属基体的黏附力;随着氧化温度的升高,氧化膜横截面的厚度不断增加,氧化膜受破坏程度也不断加剧。

Effect of carbon content on high temperature oxidation properties of Cr25Ni20 austenitic heat resistant steel

Two kinds of Cr25Ni20 austenitic heat resistant steels with different carbon content were heated to 800 and 1 100 ℃ respectively for 96 h. The cyclic oxidation curves were analyzed and the surface morphology of oxide films were observed by scan electron microscope. The composition of oxide film phase composition was analyzed by XRD method and the adhesion between oxidation film and metal substrate was measured through the scratching method. The results showed that the oxide film was made by diamond structure Cr2O3 grain and spinel structure of MnCr2O4 grain. With the increase of oxidation temperature, the oxide grains became bulky and transferred from the diamond structure into the spinel structure. The increase of carbon content caused the occurrence of "chrome poor" phenomenon, slowed down the formation of the protective oxide film and reduced the adhesive force. With the increase of oxidation temperature, the thickness of the cross section of oxide film increased and the damage degree of oxide film increased too.