粉末包埋法渗铝对Q235钢恒温抗氧化性的影响

碳钢表面渗铝可以提高材料的耐蚀性和抗高温氧化性能,选择Q235钢作为基体材料,采用固体粉末包埋法对Q235钢进行650 ℃低温渗铝处理,利用SEM、XRD和EDS研究了渗Al层的微观组织结构,通过恒温氧化实验研究渗Al处理对Q235钢700 ℃恒温氧化行为的影响.结果表明：Q235钢渗Al层主要由Fe2Al5和FeAl金属间化合物组成.渗Al层表面有裂纹和空洞,界面不平整,致密性较差,氧化膜厚度200～300μm.渗Al能显著提高Q235钢700℃的恒温氧化性能,未渗Al时Q235钢的氧化动力学曲线遵循直线规律,氧化膜主要为Fe2O3,氧化过程中氧化膜脱落严重,对基体无保护作用;渗Al后动力学曲线呈抛物线规律,氧化膜较致密,缺陷较少,氧化膜主要由Al2O3和Fe2O3组成.渗铝能显著提高Q235钢的抗高温氧化性能.

Effect of powder packing cementation-based aluminizing on isothermal oxidation properties of Q235 steel

This paper is focused specifically on a study drawing on the insight that the aluminized coating on the surface of carbon steels can improve the corrosion resistance and high temperature oxidation resistance. The study involves selecting Q235 steel as the basic material, preparing the aluminized coat- ing on its surface by pack cementation at 650 ℃, identifying the microstructure and phase constituent of the aluminized coating by SEM, XRD and EDS, and exploring the isothermal oxidation behavior at 700 ℃ in air of Q235 steel with and without aluminized coating by isothermal oxidation experiment. The results show that Q235 steel through A1 layer consisting mainly of Fe2A15 and FeA1 intermetallic com- pounds suffers from cracks and holes, uneven interface, poor compactness and the scale thickness of a- bout 200 ~ 300 p.m. Aluminizing is capable of a significant improvement in the isothermal oxidation properties of Q235 steel at 700 ℃. This is validated by the contrast that before aluminized, Q235 steel follows linear rule for the oxidation kinetics curve and thus has the scale thickness mainly in the form of Fe2 03, which fails to protect the matrix due to the serious spallation during oxidizing process, while alu- minized Q235 steel keeping to parabolic rule for oxidation kinetics curve boasts a oxide film composed mainly of Al2 O3 and Fe2 O3 , showing an increased compactness and fewer defects. It follows that alumini- zing promises a greater improvement in high temperature oxidation resistance of Q235 steel.