Ti65合金磷酸盐涂层抗高温氧化性能研究

目的通过表面涂层提高高温钛合金Ti65的抗高温氧化性能。方法采用喷涂法在Ti65合金基体上制备以磷酸铝为粘结剂、Al和Al/SiC为填料的两种磷酸盐抗高温氧化复合涂层。研究Ti65合金和涂层样品在650℃准等温、静态空气条件下的氧化动力学行为。用XRD和SEM/EDS分别对涂层样品氧化前后的物相组成、组织形貌和微区成分进行表征分析;用电子探针(EPMA)分析涂层样品的元素分布情况。结果650℃抗高温氧化实验结果表明,磷酸盐涂层样品的准等温氧化动力学曲线均符合抛物线规律,两种涂层样品的抛物线氧化速率常数kp分别为3.922×10^-2、1.768×10^-2 mg/(cm^2·h^1/2)和2.48×10^-2、3.385×10^-4 mg/(cm^2·h^1/2),均小于Ti65合金,氧化增重显著降低。以Al/SiC为填料的磷酸铝涂层的抗氧化性能最好,氧化1000 h,质量增加0.20 mg/cm^2,约为Ti65基体氧化增重(1.13 mg/cm^2)的1/6。微观分析结果表明,两种磷酸盐涂层样品在650℃准等温氧化后,涂层与基体形成扩散层,生成TiAl3金属间化合物,涂层表面均保持完好,没有裂纹和孔隙,有效阻止了氧元素向Ti65基体的扩散,保护基体不受氧化。结论磷酸盐涂层能有效阻止650℃温度下氧向Ti65合金基体的扩散,具有优异的抗高温氧化性能。

High Temperature Oxidation Resistance of Phosphate Coatings on Ti65 Alloy

The work aims to improve the high temperature oxidation resistance of Ti65 with surface coating.Two types of high temperature oxidation resistance phosphate coatings were prepared on Ti65 alloy surface by spray with aluminum phosphate as the binder and Al particles and Al/SiC particles as the fillers.Oxidation behavior of Ti65 alloy and coated sample was investigated in quasi-isothermal static air of 650℃.XRD and SEM/EDS were used to characterize and analyze phase composition,microstructure and chemical composition of micro-area of the coated samples before and after oxidation test.EPMA was used to analyze the distribution of elements.From the results of high temperature oxidation test at 650℃,the quasi-isothermal oxidation kinetics curves of phosphate coating samples all conformed to parabolic laws and both coated samples had lower parabolic oxidation rate constant kp of 3.922×10^-2,1.768×10^-2 mg/(cm^2·h^1/2)and 2.48×10^-2,3.385×10^-4 mg/(cm^2·h^1/2)than that of Ti65 alloy and the oxidation weight gain was significantly decreased.The aluminum phosphate coating with Al/SiC as fillers had the best oxidation resistance and the weight gain was 0.20 mg/cm2 after oxidation for 1000 h,which was about 1/6 of that of Ti65 base alloy(1.13 mg/cm^2).From the microscopic analysis results,after quasi-isothermal oxidation at 650℃,an intermetallic(TiAl3)diffusion layer was formed between the coating and substrate alloy.Both coatings kept perfect without any crack and pore and effectively prevented the diffusion of oxygen into the Ti65 substrate,thus protecting the substrate from oxidation.Phosphate coating can effectively prevent oxygen diffusion to Ti65 alloy substrate at 650℃,and has excellent high temperature oxidation resistance.