激光冲击强化42CrMo钢磨损与腐蚀性能研究

发布时间：2018-11-04 08:36

【摘要】：42CrMo钢作为石油领域常用的合金工具钢,因其经常工作在非常复杂的环境中,因此要求其具有良好的耐腐蚀及耐磨损性能。而激光冲击强化作为近几十年间迅猛发展起来的新型材料表面强化技术,因其相比传统表面强化技术具有强化层微观结构及残余应力状态均表现出较高稳定性的优点,因此常将其用于提高材料的耐腐蚀、疲劳及磨损性能。本文以42CrMo钢为研究对象,通过激光冲击试验、有限元模拟分析及腐蚀电化学和摩擦磨损试验研究42CrMo钢激光冲击强化诱导残余应力场的大小和分布及材料耐腐蚀和耐磨损性能,主要研究工作如下:(1)采用有限元模拟软件ABAQUS对激光冲击诱导残余应力场进行模拟仿真分析,研究激光冲击强化后残余应力在表面及深度方向的大小和分布。研究表明:激光冲击应力波传播理论时间与数值模拟结果所得到的时间误差很小。3种激光功率密度的最大残余应力值均存在于靶材表面。随着表面及深度方向远离冲击中心,残余压应力值也随之减少。激光冲击表面影响半径为2.0mm,在深度方向的影响深度为0.3mm。利用激光冲击仪器对42CrMo钢进行激光冲击强化试验,研究42CrMo钢试样激光冲击强化前后硬度、粗糙度及残余应力变化。结果表明:42CrMo钢激光冲击处理后在材料表面产生了残余压应力层,残余压应力影响层深度约为0.6mm;与未经过冲击处理的试样相比,冲击后试样的表面残余压应力值提高3~4倍,冲击试样的表面硬度分别提高了3.9%、8.6%和16.9%。激光功率密度为11.32GW/cm2的表面粗糙度明显大于5.66 GW/cm2,与未进行冲击处理试样的表面粗糙度,其粗糙度值为4.02μm。(2)在UMT-2摩擦磨损试验机上对激光冲击前后42CrMo钢试样进行摩擦磨损试验,分析激光冲击参数对42CrMo钢摩擦系数、磨损量及磨痕形貌的影响。结果表明:与未处理试样相比,激光冲击试样的摩擦系数和磨损量均随激光功率密度的增加而降低,2次冲击和3次冲击的摩擦系数分别为0.548和0.492,相比未冲击试样分别降低了14.9%和39.1%。激光冲击前试样的磨损机理为接触疲劳磨损,冲击处理后42CrMo钢试样磨损机理以磨粒磨损为主,激光冲击明显改善了42CrMo钢的摩擦磨损性能。(3)对42CrMo钢在海水腐蚀环境3%NaCl溶液中进行电化学腐蚀试验,研究42CrMo钢腐蚀热力学、腐蚀动力学参数及腐蚀表面形貌。结果表明:与未处理试样相比,激光冲击处理后42CrMo试样表面自腐蚀电位最高正移量约为0.069V,表现出较低的腐蚀倾向;自腐蚀电流密度正移,最小腐蚀电流密度存在于功率密度5.66GW/cm2、2次激光冲击试样,表现出较低的腐蚀速度。激光冲击处理后的腐蚀形貌较为平整,腐蚀凹坑减少,说明激光冲击处理能够显著提高42CrMo钢表面的电化学腐蚀性能。
[Abstract]:As a commonly used alloy tool steel in petroleum field, 42CrMo steel is required to have good corrosion resistance and wear resistance because it often works in very complex environment. Laser impact hardening, as a new material surface strengthening technology, has been developed rapidly in recent decades. Compared with the traditional surface strengthening technology, laser impact strengthening has the advantages of high stability of the microstructure and residual stress state of the strengthened layer. Therefore, it is often used to improve the corrosion resistance, fatigue and wear properties of materials. In this paper, the size and distribution of the residual stress field induced by laser shock hardening and the corrosion and wear resistance of 42CrMo steel were studied by laser shock test, finite element simulation analysis and corrosion electrochemical and friction wear test. The main research work is as follows: (1) the residual stress field induced by laser shock is simulated and analyzed by finite element simulation software ABAQUS, and the magnitude and distribution of residual stress in the surface and depth direction after laser shock hardening are studied. The results show that the theoretical time of laser shock stress wave propagation and the time error obtained by numerical simulation are very small, and the maximum residual stress values of the three laser power densities all exist on the surface of the target. The residual compressive stress decreases with the direction of surface and depth away from the impact center. The influence radius of laser shock surface is 2.0 mm, and the influence depth in depth direction is 0.3 mm. The hardness, roughness and residual stress of 42CrMo steel samples before and after laser shock hardening were studied by means of laser impact test. The results show that the residual compressive stress layer is formed on the surface of 42CrMo steel after laser shock treatment, and the depth of the layer affected by residual compressive stress is about 0.6 mm. Compared with the samples without impact treatment, the surface residual compressive stress of the impact samples was increased by 3 ~ 4 times, and the surface hardness of the impact samples was increased by 3.9% and 16.9%, respectively. The surface roughness of the laser power density of 11.32GW/cm2 is obviously greater than that of 5.66 GW/cm2, and the surface roughness of untreated samples. The roughness was 4.02 渭 m. (2) the friction and wear tests of 42CrMo steel before and after laser impact were carried out on UMT-2 friction and wear tester. The effects of laser impact parameters on the friction coefficient, wear amount and wear trace morphology of 42CrMo steel were analyzed. The results show that the friction coefficient and wear rate of laser impact samples decrease with the increase of laser power density, and the friction coefficients of two and three shocks are 0.548 and 0.492, respectively. Compared with the unimpact specimen, the ratio was decreased by 14. 9% and 39. 1%, respectively. The wear mechanism of the samples before laser impact is contact fatigue wear, and the wear mechanism of 42CrMo steel specimens after impact treatment is mainly abrasive wear. The friction and wear properties of 42CrMo steel were obviously improved by laser shock. (3) the corrosion thermodynamics, corrosion kinetic parameters and corrosion surface morphology of 42CrMo steel were studied by electrochemical corrosion test of 42CrMo steel in 3%NaCl solution in seawater corrosion environment. The results show that the maximum positive shift of the surface corrosion potential of the 42CrMo specimen after laser shock treatment is about 0.069 V, which shows a lower corrosion tendency than that of the untreated sample. The corrosion current density is positive shift, the minimum corrosion current density exists in the power density 5.66GW / cm ~ (2) laser shock sample, showing a lower corrosion rate. After laser shock treatment, the corrosion morphology is relatively flat and the corrosion pits are reduced, which indicates that laser shock treatment can significantly improve the electrochemical corrosion performance of 42CrMo steel surface.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1;TG665

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