热浸镀Al-10Si-1Ce的HP40Nb钢微观组织及高温氧化行为研究

Microstructure and Oxidation Resistance Behavior of Hot Dip Al-10Si-1Ce Aluminized Coating on HP40Nb Steel

采用SEM、EDS和XRD等方法,研究了HP40Nb钢热浸镀Al-10Si-1Ce合金的初始镀层、扩散处理渗层、高温氧化渗层的微观组织特征和抗高温氧化性能。结果表明:热浸镀层由初生α-Al,(α-Al+Si)共晶组织的外层和(Fe,Cr,Ni)2(Al,Si)5相的内层组成。热浸镀试样分别在800、900、1 000℃下进行4h扩散处理后,渗层中各层呈现不同的显微组织特征,且表面生成了不同氧化物:θ-Al_2O_3,θ-Al_2O_3+α-Al_2O_3,α-Al_2O_3。不同温度扩散处理的试样经1 000℃/360h高温氧化后,渗层均由外层(NiAl+Cr3Si)和内层(σ、α+Ni3Al)组成。1 000℃/4h扩散处理的试样在高温氧化过程中平均氧化速率最小、抗氧化性能最好,其原因是表面致密的单一α-Al_2O_3阻碍了氧化的进行。

In order to improve the high temperature oxidation and carburization resistance of HP40Nb steel, experiment of steel was coated by hot-dipping into a molten bath containing Al-10Si-Ce. The effect of diffuse treatment on hot-dip aluminizing steel microstructure and oxidation resistance behavior at high tem- perature was studied by means of SEM, EDS and XRD. The results show that after hot-dip Al-10Si-ICe treatment, the coating layer consisted of inner layer[ （Fe, Cr, Ni） 2 （A1, Si） 5 -] and outer layer[primary α-Al, （α＋Si）eutectic structure-]. After diffusion at 800, 900, 1 000℃ for 4h, the coatings had different microstructure characteristics , different oxides were formed on the surface： θ-Al2O3,θ-Al2O3 ＋ α-Al2O3, α-Al2O3. After the cyclic oxidation test at 1 000℃ for 360h,the coatings consisted of outer layer（NiAl＋Cr3Si） and inner layer（σ,α＋Ni3Al）. In the oxidation, the hot dipped Al-10Si-1Ce HP40Nb steel with the diffuse treatment of 1 000℃ / 4h had the minimum oxidation rate and best oxidation resistance. The reason was that the compact α-Al2O3 layer of the coating surface hindered the continuous oxidation.