钛合金挤压用含NaCl新型玻璃润滑剂的黏-温特性、热腐蚀及热障性能

Viscosity-temperature characteristics,hot corrosion,and thermal barrier properties of new glass lubricants containing NaCl for the extrusion of titanium alloys

以提高钛合金热挤压润滑效果为目的,研究了一种以磷酸盐玻璃、Si O_2和Na Cl为主要组成的新型玻璃润滑剂,通过模拟挤压实验、扫描电子显微镜以及换热系数测量装置,重点分析了不同组成比润滑剂的黏度-温度曲线、高温下润滑剂对钛合金的腐蚀作用、润滑条件下钛合金与模具钢之间的换热特征.结果表明,磷酸盐玻璃、Si O2和Na Cl的质量比为70∶20∶10的润滑剂,在600-900℃之间的黏度变化幅度较小,为1.3×105-9.4×105Pa·s,有利于提高钛合金挤压润滑效果.950℃下润滑剂与钛合金的接触时间不超过3 min时,润滑剂对钛合金坯料表面的高温腐蚀作用很小,且具有消除坯料表面原有氧化层的作用;但随高温接触时间的延长,钛合金表面的高温腐蚀程度逐渐增大.当TA15钛合金和H13模具钢的初始温度分别为900和400℃、新型润滑剂最终厚度约0.1 mm时,钛合金和模具钢之间的界面换热系数随实验时间的延长由185增加到1714W·m-（-2）·s-（-1）,而传统钛合金热挤压用硅酸盐玻璃润滑剂为286-2025 W·m-（-2）·s-（-1）,表明新型玻璃润滑剂具有较好的高温热障性能.

To improve lubrication during the hot extrusion of titanium alloys,a new type of glass lubricant based on phosphate glass,Si O_2,and Na Cl was prepared. The viscosity-temperature curve of the lubricant with different composition ratios was determined from an extrusion experiment. Corrosion by the lubricant of a titanium alloy under high temperature was analyzed via scanning electron microscope. The heat transfer characteristics between the titanium alloy and die steel was studied using heat transfer coefficient measurement equipment. The results show that the viscosity of the glass lubricant,with a mass ratio of phosphate,SiO_2,and NaCl of 70∶ 20∶ 10,varies slightly between 600 ℃ and 900 ℃,ranging from 1. 3 × 10~5 to 9. 4 × 10~5 Pa·s. This is beneficial to improvements in the extrusion and lubrication of titanium alloys. When the contact time between the new glass lubricant and the titanium alloy is not more than 3 min at 950 ℃,the new glass lubricant shows little corrosion on the surface of the titanium alloy,and serves the function of removing the original oxide layer on the alloy surface. High-temperature corrosion of the titanium alloy surface increases gradually with an increase in contact time. When the initial temperatures of the TA15 titanium alloy and H13 die steel are 900 and 400 ℃ respectively and the final thickness of the new glass lubricant is approximately 0. 1 mm,the heat transfer coefficient between the titanium alloy and diesteel increases from 185 to 1714 W·m^（-2）·s^（-1） with an increase in contact time. In a traditional silicate glass lubricant,used in the hot extrusion of titanium alloys,the heat transfer coefficient increases from 286 to 2025 W·m^（-2）·s^（-1）. This demonstrates that the proposed glass lubricant exhibits better thermal barrier properties at high temperatures than the traditional one.