Ti-Al-Mo系钛合金焊接过程的非等温氧化行为研究

Non-Isothermal Oxidation Behavior Research of Ti-Al-Mo Alloy During Welding Process

摘要:

研究了Ti-Al-Mo系钛合金熔池凝固后的高温焊缝金属在500~1300℃范围内不同温度下冷却过程中的非等温氧化行为，对比分析了空气和CO2两种气氛环境下的氧化行为机制。采用氧化增重法、XRD、SEM和XPS等分析测试手段研究了试样表面氧化程度、氧化膜形貌和物相等，结果表明：相比空气气氛，CO2气氛中试样氧化程度更低，并且其氧化层的氧化物颗粒尺寸更小，致密度更高。两种气氛下氧化层主要物相均为金红石型TiO2，在最表层为(TiO2+Al2O3)混合氧化物，并且CO2气氛下所含Al2O3比例更高。CO2气氛下的氧化层孔隙率更低，减少了CO2向内部基体的扩散，同时钛合金与CO2的热力学反应倾向显著低于空气，因此钛合金在CO2环境气氛中进行焊接将具有更低的氧化倾向，CO2可以作为钛合金焊缝金属冷却过程中一定温度范围内的保护气体。

Abstract:

Non-isothermal oxidation behavior of Ti-Al-Mo titanium alloy’s high temperature weld metal after molten pool solidified during cooling process at different temperatures in the range of 500~1300℃ was studied, and the oxidation mechanism in air and CO2 atmosphere was compared and analyzed. The surface oxidation degree of the sample, the morphology and phase of the oxide layer were studied by means of oxidation weight gain method, XRD, SEM and XPS. The results show that the oxidation degree of the sample in CO2 atmosphere is lower than that in air atmosphere, and the oxide particle size of the oxide layer in CO2 atmosphere is smaller and more compact. The main phase of oxide layer in both atmospheres is rutile TiO2. Besides, the mixed oxide of (TiO2+Al2O3) is observed in the surfacial layer, and the proportion of Al2O3 in CO2 atmosphere is higher. The oxide layer porosity in CO2 atmosphere is lower , which reduces the internal matrix diffusion of CO2. And the reaction thermodynamics inclination of the titanium alloy with CO2 is significantly lower than that with the air, so titanium alloy weld metal in the environment of CO2 atmosphere will have lower oxidation tendency. It’s proved that CO2 can be used as a protective gas in a certain temperature range during the cooling process of titanium alloy weld metal.