【作者】 朱丽娜；

【导师】 王成彪； 徐滨士；

【作者基本信息】 中国地质大学（北京） ， 地质工程， 2013， 博士

【摘要】 钻探机具是工程地质勘探中不可缺少的设备，磨损、腐蚀和疲劳等常见的表面失效严重影响其服役安全性和使用寿命。采用先进的表面工程技术对钻具零部件表面进行再制造，提高其耐磨、耐蚀以及抗疲劳性能，是保证钻探机具服役安全的有效途径。激光熔覆层和超音速等离子喷涂层具有优异的耐磨、耐蚀和抗疲劳性能，适合用于对钻具进行再制造。然而，制备过程中产生的残余应力对再制造涂层的力学性能和服役持久性具有重要影响。因此，研究再制造涂层中的残余应力大小以及分布规律对提高其使用寿命和揭示其失效机制具有重要的意义。本文采用纳米压痕技术，基于自主设计的新型等双轴残余应力施加装置，对单晶铜和45钢施加不同应力后进行纳米压痕试验，研究残余应力对压痕参数(加载、卸载曲线，压痕周围的凸起变形以及压痕接触面积)的影响规律。研究发现：相对于无应力状态，残余拉应力在固定载荷模式下会使压入深度明显增大，而在固定深度模式下，会使压入载荷明显减小；且无论何种压入模式，残余拉应力均会减小卸载时的弹性回复、压痕周围的凸起变形高度以及压痕真实接触面积。而残余压应力对压痕参数的影响则表现出相反的规律。真实接触面积是纳米压痕法测定残余应力的重要特征参量，但传统的O&P模型在计算真实接触面积时忽略了压痕周围的凸起变形面积，从而引入严重的误差。针对这一问题，本文基于几何算法，将压痕的真实接触面积看为凸起变形部分的面积与传统O&P法计算的三角形面积之和，建立了新的适用于压痕周围发生凸起变形的材料的真实接触面积计算模型，很好地修正了O&P模型的误差。基于新型的等双轴残余应力施加装置，对比分析了Suresh的固定载荷和固定深度模型，以及Lee模型在残余应力测试时的准确性和适用范围，发现Suresh和Lee模型均不适用于软质材料的残余应力计算。而对于硬质材料，Suresh的固定载荷模型计算出的残余应力值偏大，Lee模型计算出的拉应力结果存在较大误差，而采用Suresh的固定深度模型计算硬质材料的残余应力最为准确。基于Suresh固定深度模型，系统研究了Fe90激光熔覆层和FeCrBSi超音速等离子喷涂层表面以及截面上的残余应力大小和分布规律，并用X射线衍射法进行了辅助验证。发现纳米压痕法能够精确测量出致密激光熔覆层中的残余应力和孔隙较少的喷涂层表面残余应力，而对于孔隙相对较多的喷涂层截面，计算的残余应力值可能存在一定的误差。更多还原

【Abstract】 Drilling implement is indispensable equipment in engineering geological exploration. Thesecurity and service life of drilling implement are seriously affected by common surface failuresuch as wear, corrosion and fatigue. Advanced surface engineering technologies are often used toremanufature the drilling implement to improve the wear resistance, corrosion resistance andfatigue resistance, which is an effective way to ensure the service safety. Laser cladding coatingsand supersonic plasma spraying coatings having excellent wear resistance, corrosion resistanceand fatigue resistance are suitable for remanufaturing of drilling implement. However, theresidual stresses produced in the preparation process have important influence on the mechanicalproperties and service persistence of remanufatured coatings. Therefore, the study on the residualstresses of remanufatured coatings has important significance to improve the service life andreveal the failure mechanism.In this dissertation, nanoindentation tests were performed on the single crystal copper and1045steel after applied to different stresses by a new designed stress-applying device. Theeffects of residual stresses on the nanoindentation parameters such as loading and unloadingcurves, pile-up deformation around indents, and contact area were researched. The resultsshowed that compared with stress-free state, tensile stress will increase the indentation depthwhen the load is fixed, and will decrease the indentation load when the depth is fixed. No matterwhich indentation mode, the residual tensile stress will reduce the elastic recovery whenunloading, the pile-up height and contact area. While the influence of residual compressive stresson the indentation parameters shows the opposite law.The real contact area is an important characteristic parameter for the determination ofresidual stresses, but the traditional O&P model ignores the pile-up area in the calculation of thereal contact area, and thus serious errors will be introduced. Aiming at this problem, thisdissertation considered the real contact area as the sum of pile-up area and the triangle areacalculated by O&P model. The new proposed method is suitable for the area calculation ofmaterials that pile up, which well corrects the error of O&P model.Based on the new designed stress-applying device, the accuracy and applicability of theSuresh models (fixed load model and fixed depth model) and the Lee model were compared andanalyzed in the calculation of residual stresses. The Suresh models and Lee model were not suitable for soft materials. For hard materials, the residual stresses calculated by the fixed loadSuresh model were too large; the tensile stresses determined by the Lee model had big errors.The stresses calculated by the fixed depth Suresh model were the most accurate.Based on the fixed depth Suresh model, the surface and cross-section residual stresses of Fe90laser cladding coating and FeCrBSi supersonic plasma spraying coating were studied andverified by traditional X-ray diffraction method. The results showed that nanoindentation methodcan accurately measure the surface and cross-section residual stresses of the Fe90laser claddingcoating with dense structure, as well as the surface residual stress of FeCrBSi coating with lesspores. However, for the cross-section of supersonic plasma spraying coating with relatively morepores, the calculated stress value may have certain errors.更多还原