微弧氧化处理对碳钢表面耐LBE腐蚀性能的影响

Effect of Micro-arc Oxidation Treatment on Corrosion Resistance of Carbon Steel Surface to LBE

目的以Q235钢为基材,制备微弧氧化陶瓷层,提高钢铁材料耐LBE腐蚀性。方法采用TIG熔-钎焊并添加ER4043焊丝的方法,对1.5 mm厚的5A06铝合金和3 mm厚的镀锌Q235钢进行焊接,焊后对接头进行280℃保温30 min的退火热处理。同时,采用合适的微弧氧化工艺在铝/钢焊缝表面制备微弧氧化陶瓷层,研究微弧氧化处理对钢材耐LBE腐蚀性的影响。结果采用TIG熔-钎焊的方法对铝/钢异种金属进行焊接时,铝/钢界面会不可避免地产生金属间化合物层,对铝/钢熔-钎焊接头进行280℃保温30 min的退火热处理后,金属间化合物层的厚度可达9～10μm,化合物层主要由Al_8Fe_2Si相和少量的[Al,Fe,Si]、Al_(13)Fe_4相组成,接头抗拉强度高达185 MPa,且断裂发生在铝母材处。微弧氧化处理可使焊缝表面原位生成均匀的陶瓷层,陶瓷层表面呈"火山状"形貌,且"火山状"物质的中心有较多不同尺寸的放电微孔。陶瓷层主要由α-Al_2O_3、γ-Al_2O_3和莫来石相组成,且其表面粗糙度较低。Q235钢经过腐蚀后,表面出现较多的腐蚀坑,Pb、Bi元素向碳钢内部扩散;而陶瓷层经过腐蚀后,表面没有明显的腐蚀现象。结论微弧氧化处理可显著提高钢铁材料耐LBE腐蚀性,阻碍Pb、Bi元素向钢铁内部的扩散。

The work aims to improve corrosion resistance of steel materials to LBE by preparing micro-arc oxidation ceramic layer with Q235 steel as substrate.1.5 mm thick 5A06 aluminum alloy and 3 mm thick galvanized Q235 steel were welded by TIG welding-brazing combined with the ER4043 filler metal.The annealing treatment was carried out to the joints at 280℃for 30 min after welding.Meanwhile,micro-arc oxidation ceramic coatings were prepared on the surface of aluminum/steel weld seam by suitable micro-arc oxidation process in order to investigate the effect of micro-arc oxidation treatment on the corrosion resistance of steel materials to LBE.The intermetallic compound layer was inevitably formed at the interface between aluminum and steel,when the aluminum alloy and steel were welded by TIG welding-brazing.The thickness of the intermetallic compound layer reached 9~10μm after the joint by aluminum/steel welding-brazing was annealed at 280℃for 30 min.The compound layer consisted of Al8Fe2Si phases and a little[Al,Fe,Si]and Al13Fe4 phases.The tensile strength of joint was 185 MPa and the ductile fracture occurred in aluminum base metal.Uniform ceramic coatings could be formed on weld surface by micro-arc oxidation treatment.Volcano-like morphology with many micro pores could be observed on the surface of ceramic coatings and there were many discharge pores with different sizes at the center of volcanic substance.In addition,the ceramic coatings with low surface roughness were composed ofα-Al2O3,γ-Al2O3 and mullite phases mainly.Many corrosion pits were found on the surface of Q235 steel after corrosion,and lots of Pb and Bi elements diffused into the steel material.However,there were no obvious corrosion phenomenon on the surface of ceramic coatings after corrosion.Micro-arc oxidation treatment can improve the corrosion resistance of steel materials to LBE and hinder the diffusion of Pb and Bi elements into the steel material.