T91钢表面低温渗层的动力学行为

Dynamic behavior of low temperature aluminizing coating on T91 steel surface

研究了T91钢在渗铝温度区间650～750℃,活化剂添加量2%,渗铝时间2～8 h时的渗铝层形成与生长过程。结果表明：渗铝温度为650℃和700℃时,渗层为单一的Fe Al相;当渗铝温度为750℃,渗层为Fe Al与少量的Fe Al2相;渗层在渗铝温度高于700℃时,渗铝层内部出现空洞与裂纹等缺陷,裂纹的产生可能与渗层Al浓度有关。保温时间只对渗铝层厚度产生影响,不会改变渗铝层成分;渗铝层厚度会随着渗剂中的Al含量不同而发生变化。在渗铝温度650℃,保温8 h,活化剂含量2%时,得到厚度约为11. 5μm、致密的Fe Al渗层。在650～750℃温度区间渗铝温度（T）、渗铝时间（t）、渗剂Al含量（W）与渗层厚度（h）的关系可由方程式h=77. 44W1/2t1/2exp-3178. 92（）T来描述。

The formation and growth process of aluminizing coating on T91 steel surface under the conditions of aluminizing temperature of650-750 ℃,activator addition of 2% and aluminizing time of 2-8 h were studied. The results show that when the aluminizing temperature is 650 ℃ and 700 ℃,the coating is composed of Fe Al phase; when the aluminizing temperature is 750 ℃,the coating is composed of Fe Al phase and a small amount of Fe Al2 phase; when the aluminizing temperature is higher than 700 ℃,the defects such as cavity and cracks are observed in the aluminizing coating. The formation of cracks may be related to the concentration of Al in the coating. The holding time only affects the thickness of the aluminizing coating and will not change the composition of the aluminizing coating,and the thickness of the aluminizing coating will change with the Al content of the aluminizing agent. In the experiment,when the activator content is 2% and aluminizing is conducted at 650 ℃ for 8 h,the dense Fe Al coating with the thickness of 11. 5 μm can be obtained. The relationship between the thickness of the coating（ h）,aluminizing temperature（ T）,aluminizing time（ t） and Al content（ W） in the temperature range of 650-750 ℃ can be described by equation h = 77. 44 W1/2 t1/2 exp-3178. 92（）T.