显微组织对微纳结构贝氏体钢海洋腐蚀行为的影响

Effect of microstructure on marine corrosion behavior of micro/nano-structured bainitic steel

以一步、两步贝氏体转变及不同热处理工艺获得的微纳结构贝氏体钢为对象,利用组织表征、电化学测试及中性盐雾试验,研究显微组织对其海洋腐蚀行为的影响。结果表明:试验钢的显微组织主要由贝氏体铁素体板条(BF)、马氏体-奥氏体复合组织(block M-A)和薄膜状残余奥氏体(film RA)组成。随着腐蚀周期的增加,试验钢的腐蚀速率均呈下降趋势,腐蚀产物主要由γ-FeOOH、α-FeOOH、α-Fe_(2)O_(3)和Fe_(3)O_(4)组成。腐蚀后期,γ-FeOOH转化为稳定的α-FeOOH,提高了锈层的保护性。相对一步贝氏体钢,二步贝氏体钢中残余奥氏体含量较低,主要形态为薄膜状,强度与韧性明显提升;二步贝氏体钢的腐蚀产物中α-FeOOH的比率更高,锈层更加致密,腐蚀速率较低,耐腐蚀性能更为优异。

The micro/nano-structure bainitic steels obtained by one-step and two-step bainite transformation and different heat treatment processes were obtained,and the influence of microstructure on the marine corrosion behavior of micro/nano-structured bainitic steel was studied by means of microstructure characterization,electrochemical test and neutral salt spray test.The results show that the microstructure of the test steel is mainly composed of bainitic ferrite lath(BF),martensite-austenite composite structure(block M-A)and film-like retained austenite(film RA).With the increase of corrosion cycle,the corrosion rates of the test steels all show a declining trend,and the main corrosion products are composed ofγ-Fe OOH,α-Fe OOH,α-Fe_(2)O_(3) and Fe_(3)O_(4).In the later stage of corrosion,γ-Fe OOH is converted into stableα-Fe OOH,which improves the protection of the rust layer.Compared with the one-step bainitic steel,two-step bainitic steel has lower volume fraction with main morphology of thin film,which largely improves strength and toughness.The higher ratio ofα-Fe OOH in two-step bainitic steel contributes to denser rust layer,resulting in lower corrosion rate and enhances corrosion resistance than that of one-step bainitic steel.