包埋时间对N80套管钢表面渗铝层组织和性能的影响

为提高套管钢的耐腐蚀性能,在950℃对N80套管钢分别进行了2 h、4 h及6 h的包埋渗铝工艺处理.不同包埋时间下所得渗层的物相组成、微观形貌、显微硬度和电化学性能不同.测试结果表明:渗铝时间为2 h时,所得渗铝层厚度为150μm,渗铝时间延长到4 h和6 h后,渗铝层厚度增大到300μm;渗铝时间为2 h、4 h时所得N80套管钢的渗铝层主要由FeAl金属间化合物组成,当渗铝时间为6 h时,渗铝层中开始出现了高铝Fe2Al5相;不同时间包埋渗铝处理后的N80套管钢试样表面硬度高于基体,自腐蚀电流密度显著下降.由此得出结论:高铝相铁铝化合物随包埋时间的延长开始出现;渗铝层厚度随包埋时间的延长有所增加,当包埋时间超过4 h后,包埋时间对渗铝层致密度的提高作用较厚度增加更为显著;延长包埋时间可以显著提高渗铝层的硬度,但过长的包埋时间会同时造成基体硬度严重地下降;包埋时间对腐蚀性能的影响作用不明显.

Effects of embedding time on the microstructure and properties of aluminized N80 casing steel

In order to improve the corrosion resistance of casing steel,the pack aluminizing to N80 casing steel is carried at 950 ℃ for 2 h,4 h and 6 h.By analyzing the microstructure,phase composition,microhardness and electrochemical corrosion resistance of the aluminized N80 casing steel,it is shown that the thickness of the packed aluminizing layer increase from 150 μm to 300 μm as the embedding time is prolonged from 2 h to 4 h and 6 h.FeAl is the main phase in the aluminizing layer when the aluminizing time is 2 h and 4 h,and the content Fe₂Al₅ appears in the aluminizing layer when the embedding time is 6 h.Compared with non-aluminized N80 casing steel,the microhardness and the corrosion resistance of the aluminized N80 casing steel can be improved.Therefore,these conclusions can be obtained:the thickness of the obtained aluminizing layer will increase with embedding time,the density improvement of the aluminizing layer are better than its thickness improvement with the increasing of embedding time.Additionally,the prolonging embedding time can improve the microhardness of the aluminizing layer,but too long embedding time will make the microhardness of N80 casing steel base material decrease.The effect of embedding time on the corrosion resistance of aluminized N80 casing steel is not obvious.