喷射成形7075铝合金钻杆的摩擦性能研究

Study on Friction Properties of Spray Deposited 7075 Aluminium Alloy Drill

采用喷射成形技术制备出晶粒细小组织均匀的7075铝合金坯料,平均粒径约10μm;把坯料半固态挤压成圆管,挤压温度为520℃,再进行固溶+时效处理,固溶温度490±5℃,保温时间1.5 h,冷却介质为水(室温);时效温度190±5℃,保温时间12 h。采用高温摩擦磨损试验仪,在干摩擦条件下分别测试载荷和速度对摩擦系数和磨痕的影响。实验结果表明:干摩擦条件下,磨损量和摩擦系数随着载荷和速度增大而增大,载荷比速度对磨损量和摩擦系数影响更大。磨损机理:当载荷小于临界值15 N,磨损机制以塑性变形主导,由塑性变形转变成犁沟推挤和剥层磨损。当载荷大于15 N磨损机制以氧化磨损主导,由塑性变形转变成氧化磨损和剥层磨损。当速度小于临界值600 r/min,磨损机制以塑性变形为主导,速度越大材料软化越强,塑性变形引起的犁沟效应越强。当速度大于600 r/min,磨损机制以氧化磨损和剥层磨损为主导,由轻微磨损到严重磨损再到轻微磨损的转变。

7075 aluminum alloy as a drill pipe is widely used in oil and gas drilling, the study of 7075 aluminum alloy friction performance is of great significance. In this paper, 7075 aluminum alloy blanks with uniform grain size were prepared by spray-deposition technology. The average particle size was about 10 μm. Secondly, Drill pipe was extruded at520 ℃ in the semi-solid and then treated by solid solution+failure, the solution temperature is 490±5 ℃, holding time is 12 hours. Finally, the influence of load and velocity on friction coefficient and wear scar was tested under dry friction condition by high temperature friction and wear tester. The experimental results show that under the dry friction condition,the wear extent and the friction coefficient increase with the increase of the load and velocity, and the load has a greater effect on the wear extent and the friction coefficient. Wear mechanism: When the load is less than the critical value of 15 N, wear mechanism dominated by plastic deformation, from plastic deformation into furrow and stripping wear. When the load is greater than 15 N, wear mechanism dominated by the oxidation wear, from plastic deformation into oxidative wear and stripping wear. When the velocity is less than the critical value of 600 r/min, the wear mechanism is dominated by plastic deformation, the greater the speed, the stronger the softening of the material, the stronger the furrow effect caused by the plastic deformation. When the speed is greater than 600 r/min, the wear mechanism is dominated by oxidative wear and stripping wear, from slight wear to severe wear and slight wear.