稀土La对渗铝层及其抗高温氧化性能的影响

Effect of La on Formation Process and Resistance to High-Temperature Oxidation of Aluminizing Coating

稀土元素La对传统的铝层的结构及其抗高温氧化性能的影响机理尚未充分定型。以低碳钢为基体,预置纯镍和Ni-La2O3复合电镀层,采用固体粉末法进行渗铝,对渗铝试样进行高温氧化试验。用光学显微镜(OM)、扫描电镜及能谱(SEM/EDAX)等方法对试样进行了分析,发现稀土元素La促进了渗铝的过程,使渗铝层中铝含量较高,质量分数为35%,并且渗层组织细小均匀,表面质量好;高温氧化后,Ni-La镀层渗铝层表面形成的氧化膜薄而致密,氧化增重较小,具有较好的抗高温氧化性能。

Low carbon steels were pre-coated with pure Ni and Ni-La2 O3 composite coatings by electrodeposition.The pre-coated steel samples were then aluminized using pack ce-mentation method,and the antioxidation performance of the alu-minizing coating at high temperatures was evaluated using high-temperature oxidation tests,aiming at revealing the effects of rare earth element La on the resistance to high-temperature oxidation of the aluminizing coating.Moreover,the composition and micro-structure of the aluminizing coating were analyzed by means of op-tical microscopy,scanning electron microscopy,and energy dis-persive spectrometry.Results showed that La contributed to pro-mote the aluminizing process and hence increase the Al content(as high as 35 wt%)in the aluminizing coating.At the same time,the introduction of La helped to refine the microstructure and improve the apparent quality of the aluminizing coating.And the aluminizing coating formed after high-temperature oxidation of Ni-La2O3 composite coating was thin and compact,and it showed less weight loss by high-temperature oxidation and good resistance to oxidation at high temperature.