火箭橇滑块摩擦磨损失效机理及形貌特征分析

Investigation on Friction and Wear Topography Features and Failure Mechanism of Slide of Rocket Sled

目的为火箭橇滑块的表面磨损及其失效分析提供参考。方法选取火箭橇试验后的铜合金滑块为研究对象,采用电子显微镜、能谱仪、三维形貌仪和X射线衍射分析仪对摩擦磨损表面进行观察,并借助维氏硬度计和金相显微镜测试截面硬度及其组织结构变化。结果通过电子显微镜与能谱仪分析发现,试验后,滑块的表面存在沿摩擦方向的划痕、脱落颗粒、点蚀坑和粘着点,磨损形式有磨粒磨损和粘着磨损,对磨件上Fe等元素向滑块转移。由三维形貌分析可知,滑块表面出现很深的平行犁沟、撕裂状的表面、不规则裂纹和塑性堆积层。由X射线衍射分析可知,滑块表面形成了新的物相组织。通过维氏硬度计和金相显微镜分析滑块截面发现,由于加工硬化,沿表面至深度2.5 mm,硬度由129HV降低到95HV,降低约26%,且组织结构也随之发生变化。结论分析认为,干摩擦过程中火箭橇滑块表面聚集大量热能,导致温度沿截面呈明显梯度变化,因而引起组织结构随之变化,进而出现磨粒磨损和粘着磨损两种典型现象。加工硬化引起表面塑性降低,硬度沿截面方向呈梯度变化。

The work aims to provide reference by analyzing the surface wear and the failure of the rocket sled. The copper alloy in the rocket sled after test was selected as the experimental material, the surface wear morphology of copper alloy was observed by SEM, energy spectrometer, three dimensional morphometer and X ray diffraction device(XRD), and the hardness of cross section and the change of structure were measured by hardness tester and metallurgical microscope. By SEM and energy spectrometer, after test, the scratches along friction direction, broken particles, corrosion pit and adhesive particles appeared on surface of sled, the forms of wear included abrasive wear and adhesive wear, and the chemical element in grinding part transferred to sled. From the analysis on three-dimensional morphology, deep parallel furrow, fractured surface, irregular crack and plastic stacking layer were observed on sled surface. By XRD, the new phase and microstructure were also observed on the surface of sled. From the analysis on cross section of sled by Vickers hardness tester and metallurgical microscope, along the thickness direction in the range of 2.5 mm, the hardness value reduced to 95 HV from 129 HV because of machining hardening, and the microstructure also changed. Through the analysis, in dry friction process of rocket sled, lots of heat is aggregated on the sled surface, and temperature gradient appears along thickness direction of rocket sled, so the microstructure changes along the thickness of sled, and the abrasive wear and adhesive wear are observed. Because of machining hardening, the plasticity is reduced, and the gradient of hardness and is also formed.