钛基梯度功能涂层组织和腐蚀行为研究

Microstructure and Corrosion Behavior of Ti-Matrix Functional Gradient Layer

为开发在高温环境、大温差条件下具有热应力缓和功能的新型耐蚀涂层,应用Nd:YAG激光在钛合金表面制备了钛基FGM和N-FGM,观察了微观组织,测量了显微硬度变化规律以及FGM和Ti600基体的耐腐蚀性能。结果表明,原位合成的TiC球状增强体弥散分布在FGM中,主要呈3种不同的形态:粗大的或不完整的树枝晶,相对较为细小的等轴或近似等轴晶和细小短纤维状晶。由于快速凝固的微观结构和大量弥散均匀分布的TiC增强相,FGM和N-FGM显微硬度值均较高,平均约为1450HV,是Ti600基材(310HV)的4.5～5倍。且随梯度层中TiC增强相含量的减少,FGM显微硬度值连续梯度降低。Ti600基体和FGM耐蚀性均较好;极化电位较低;自腐蚀电流密度小,在10-8 A.cm-2范围。FGM耐蚀性能较Ti600得到提高,腐蚀电流密度和电阻值分别为Ti600的0.72和1.31倍。

To development a new corrosion resistant layer with alleviating thermal stress function under hyperthermal and big difference in temperature conditions,research of producing Ti-matrix FGM and N-FGM on Ti600 substrates by pulsed Nd：YAG had been carried out.The microstructures and microhardness of FGM were investigated.The corrosion properties of FGM and Ti600 substrate were examined.It was found that in-situ synthesized TiC reinforced phase distributed in FGM evenly in the form of globular grains,which had three main different shapes,such as bulky or imperfect arborescent crystal,fine or approximately equiaxial crystal and chopped fibriform crystal.FGM and N-FGM had an average hardness of approximately 1450 HV,4.5～5 times than that of Ti600 substrates,attributing to a rapidly solidified microstructure and TiC primary dendrites.With the reducing of weight percentage of TiC,microhardness of FGM decreased gradiently and continuously.The corrosion resistance of FGM and Ti600 was good.Polarization potential was low and the corrosion current was around 10-8 A·cm-2 level.Otherwise,the corrosion resistance of FGM was improved.Corrosion current and resistance were 0.72 and 1.31 times than that of Ti600 substrates,respectively.