【摘要】：42CrMo鋼作為石油領域常用的合金工具鋼,因其經(jīng)常工作在非常復雜的環(huán)境中,因此要求其具有良好的耐腐蝕及耐磨損性能。而激光沖擊強化作為近幾十年間迅猛發(fā)展起來的新型材料表面強化技術,因其相比傳統(tǒng)表面強化技術具有強化層微觀結構及殘余應力狀態(tài)均表現(xiàn)出較高穩(wěn)定性的優(yōu)點,因此常將其用于提高材料的耐腐蝕、疲勞及磨損性能。本文以42CrMo鋼為研究對象,通過激光沖擊試驗、有限元模擬分析及腐蝕電化學和摩擦磨損試驗研究42CrMo鋼激光沖擊強化誘導殘余應力場的大小和分布及材料耐腐蝕和耐磨損性能,主要研究工作如下:(1)采用有限元模擬軟件ABAQUS對激光沖擊誘導殘余應力場進行模擬仿真分析,研究激光沖擊強化后殘余應力在表面及深度方向的大小和分布。研究表明:激光沖擊應力波傳播理論時間與數(shù)值模擬結果所得到的時間誤差很小。3種激光功率密度的最大殘余應力值均存在于靶材表面。隨著表面及深度方向遠離沖擊中心,殘余壓應力值也隨之減少。激光沖擊表面影響半徑為2.0mm,在深度方向的影響深度為0.3mm。利用激光沖擊儀器對42CrMo鋼進行激光沖擊強化試驗,研究42CrMo鋼試樣激光沖擊強化前后硬度、粗糙度及殘余應力變化。結果表明:42CrMo鋼激光沖擊處理后在材料表面產生了殘余壓應力層,殘余壓應力影響層深度約為0.6mm;與未經(jīng)過沖擊處理的試樣相比,沖擊后試樣的表面殘余壓應力值提高3~4倍,沖擊試樣的表面硬度分別提高了3.9%、8.6%和16.9%。激光功率密度為11.32GW/cm2的表面粗糙度明顯大于5.66 GW/cm2,與未進行沖擊處理試樣的表面粗糙度,其粗糙度值為4.02μm。(2)在UMT-2摩擦磨損試驗機上對激光沖擊前后42CrMo鋼試樣進行摩擦磨損試驗,分析激光沖擊參數(shù)對42CrMo鋼摩擦系數(shù)、磨損量及磨痕形貌的影響。結果表明:與未處理試樣相比,激光沖擊試樣的摩擦系數(shù)和磨損量均隨激光功率密度的增加而降低,2次沖擊和3次沖擊的摩擦系數(shù)分別為0.548和0.492,相比未沖擊試樣分別降低了14.9%和39.1%。激光沖擊前試樣的磨損機理為接觸疲勞磨損,沖擊處理后42CrMo鋼試樣磨損機理以磨粒磨損為主,激光沖擊明顯改善了42CrMo鋼的摩擦磨損性能。(3)對42CrMo鋼在海水腐蝕環(huán)境3%NaCl溶液中進行電化學腐蝕試驗,研究42CrMo鋼腐蝕熱力學、腐蝕動力學參數(shù)及腐蝕表面形貌。結果表明:與未處理試樣相比,激光沖擊處理后42CrMo試樣表面自腐蝕電位最高正移量約為0.069V,表現(xiàn)出較低的腐蝕傾向;自腐蝕電流密度正移,最小腐蝕電流密度存在于功率密度5.66GW/cm2、2次激光沖擊試樣,表現(xiàn)出較低的腐蝕速度。激光沖擊處理后的腐蝕形貌較為平整,腐蝕凹坑減少,說明激光沖擊處理能夠顯著提高42CrMo鋼表面的電化學腐蝕性能。
[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.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG142.1;TG665

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