模拟高温海洋环境中铝化物/搪瓷复合涂层腐蚀行为研究

Corrosion Behavior of Enamel/aluminide Composite Coating in a Simulated High Temperature Marine Environment

对镍基高温合金GH4169基体先采用包埋渗铝工艺制备铝化物涂层,随后在渗铝涂层表面喷烧搪瓷涂层,得到了渗铝+搪瓷复合涂层。该涂层外层由搪瓷涂层组成,厚度约为40μm;中间层为渗铝涂层,厚度约20μm,主要为Ni_(2)Al_(3)相,搪瓷涂层和渗铝涂层结合良好;内层为互扩散区,厚度约为3μm。分别考察了搪瓷+渗铝复合涂层、渗铝涂层和GH4169合金基体在650℃NaCl+水蒸汽+氧气中进行模拟高温海洋环境腐蚀实验。结果表明,渗铝涂层和合金中的Fe和Cr在NaCl+水蒸汽协同腐蚀作用下发生氧化-氯化自催化反应,表面的氧化膜破坏严重。搪瓷涂层隔绝了NaCl和水蒸汽等腐蚀介质,从而阻断氧化-氯化自催化反应,保护了渗铝涂层和合金。

The enamel/aluminide composite coating on Ni-based superalloy GH4169 is prepared by two-step process i.e,pack cementation and subsequent spray/fired enamel coating.The coating mainly consists of three layers:the outer layer of enamel coating(40μm),and the middle layer of aluminide coat-ing mainly composed of Ni_(2)Al_(3) phase(~20μm),and the inner layer of an interdiffusion zone of about 3μm in thickness.The corrosion behavior of enamel/aluminide composite coating/GH4169,aluminide coating/GH4169 and blank GH4169 alloy respectively were investigated beneath NaCl deposits in atmo-sphere of oxygen flow carrying water vapor.The results show that the oxidation and chlorination of ele-ments Fe and Cr in the aluminide coating and alloy can autocatalytically ocurr due to the presence of syn-ergistic reaction of NaCl with water vapor,thereby the oxide scale on the surface is seriously damaged.The enamel coating could isolate the corrosive media such as NaCl and water vapor from the aluminide coating/GH4169,thus blocking the oxidation-chlorination autocatalytic reaction,thereby,the corrosion of the aluminide coating/alloy is retarded.