發(fā)布時間：2019-01-05 04:47

【摘要】：激光熔化沉積(laser melting deposition,LMD)在航空航天、醫(yī)療器械等領(lǐng)域具有廣泛的應(yīng)用前景。但由于該技術(shù)本身所固有的驟熱、驟冷特點,沉積件內(nèi)部大多存在殘余應(yīng)力、氣孔等微觀缺陷,制約了零件的推廣和應(yīng)用。為此,本文提出電磁沖擊增強金屬激光熔化沉積技術(shù)方法,以期通過電磁力對熔池附近高溫沉積層施加沖擊,起到在線降低制件內(nèi)部殘余應(yīng)力、減少孔隙等缺陷的作用。本文以激光熔化沉積鐵基粉末、316L不銹鋼基板為例進行該方法的研究,具體研究內(nèi)容如下:(1)研究電磁沖擊增強激光熔化沉積的理論基礎(chǔ),包括對沉積層所受電磁力的推導(dǎo)分析,激光熔化沉積殘余應(yīng)力的產(chǎn)生及控制方法研究,以及電磁沖擊消減激光熔化沉積制件內(nèi)殘余應(yīng)力的機理的初步分析。(2)運用有限元技術(shù)獲得了平面螺旋線圈作用下沉積層內(nèi)感應(yīng)電磁力的時間、空間分布特性以及不同電參數(shù)及幾何參數(shù)下內(nèi)電磁力的分布規(guī)律,確定線圈施力區(qū)域,提出集磁器線圈,并對其進行優(yōu)化設(shè)計。從仿真結(jié)果得出,集磁器上表面半徑與勵磁線圈半徑相同,下表面與內(nèi)孔半徑較小時更適合電磁沖擊增強激光熔化沉積試驗。此外,電流強度較高時,電磁力更大,更有利于沖擊效果。(3)根據(jù)仿真參數(shù)搭建電磁沖擊增強激光熔化沉積裝置并完成不同勵磁電流下的單道、多層多道沉積件制作,并與常規(guī)制件進行對比。(4)對制件微觀組織、孔隙、殘余應(yīng)力等方面進行分析,結(jié)果表明:電磁場的施加有利于制件晶粒細化,顯微硬度增加、孔隙數(shù)量和平均尺寸的下降,沉積層顯微組織一次枝晶間距由5μm降低至3.2μm,內(nèi)部殘余應(yīng)力最大降低49%。
[Abstract]:Laser melt deposition (laser melting deposition,LMD) has been widely used in aerospace, medical equipment and other fields. However, due to the inherent characteristics of sudden heat and sudden cooling, the microcosmic defects such as residual stress, porosity and so on exist in the deposition parts, which restrict the popularization and application of the parts. In this paper, a method of electromagnetic shock enhanced laser melting deposition of metals is proposed in this paper. It is expected that the electromagnetic force will exert an impact on the high temperature deposit near the molten pool, which can reduce the internal residual stress of the parts and reduce the defects such as pores on line. In this paper, the method of laser melting deposition of iron-based powder and 316L stainless steel substrate is studied. The main contents are as follows: (1) the theoretical basis of electromagnetic shock enhanced laser melting deposition is studied. Including the derivation and analysis of electromagnetic force, the generation and control of residual stress in laser melt deposition. The mechanism of reducing residual stress in laser melted deposition parts by electromagnetic shock is analyzed. (2) the time of inductive electromagnetic force in the deposit layer under the action of planar spiral coil is obtained by using finite element technique. According to the spatial distribution characteristics and the distribution law of electromagnetic force in different electric and geometric parameters, the force region of the coil is determined, and the magnetic collector coil is proposed and optimized. From the simulation results, it is concluded that the upper surface radius of the collector is the same as that of the excitation coil, and the radius of the lower surface and the inner hole is more suitable for the electromagnetic shock enhanced laser melting deposition test. In addition, when the current intensity is high, the electromagnetic force is larger, which is more favorable to the impact effect. (3) according to the simulation parameters, the electromagnetic shock enhancement laser melting deposition device is built and the single channel, multi-layer and multi-channel deposition parts are made under different excitation current. And compared with the conventional parts. (4) the microstructure, pore and residual stress of the parts are analyzed. The results show that the application of electromagnetic field is beneficial to the grain refinement and the increase of microhardness of the parts. With the decrease of the number of pores and the average size, the primary dendritic spacing of the deposited layer decreases from 5 渭 m to 3.2 渭 m, and the internal residual stress decreases by 49%.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG665

【參考文獻】

相關(guān)期刊論文 前10條

1 戚永愛;趙劍峰;謝德巧;李悅;;超聲沖擊細化FGH95鎳基高溫合金激光熔覆層組織[J];焊接學報;2015年03期

2 陳曉偉;王文平;萬敏;熊威人;龍安林;;平板件電磁成形技術(shù)的研究進展[J];稀有金屬材料與工程;2015年02期

3 蔣帥;李懷學;石志強;王玉岱;黃柏穎;周永強;;熱等靜壓對激光直接沉積Ti60合金組織與拉伸性能的影響[J];紅外與激光工程;2015年01期

4 趙劍峰;馬智勇;謝德巧;韓雪謙;肖猛;;金屬增材制造技術(shù)[J];南京航空航天大學學報;2014年05期

5 解航;張安峰;李滌塵;賀斌;楊洪濤;;激光金屬直接成形Ti6Al4V-CoCrMo梯度材料開裂研究[J];中國激光;2013年11期

6 張升;桂睿智;魏青松;史玉升;;選擇性激光熔化成形TC4鈦合金開裂行為及其機理研究[J];機械工程學報;2013年23期

7 李忠;張偉;李春峰;于海平;;線圈結(jié)構(gòu)參數(shù)對電磁成形的影響[J];塑性工程學報;2013年01期

8 鐘文華;劉貴仲;葛大梁;高原;;Cr_3C_2對鎳基碳化鎢激光熔覆層組織與性能的影響[J];金屬熱處理;2012年07期

9 王凱;楊海歐;劉奮成;林鑫;黃衛(wèi)東;;基板預(yù)變形下激光立體成形直薄壁件應(yīng)力和變形的有限元模擬[J];中國激光;2012年06期

10 肖師杰;莫健華;崔曉輝;;并列線圈在平板電磁成形中的磁場力分布與受力分析[J];新技術(shù)新工藝;2012年04期

相關(guān)碩士學位論文 前5條

1 劉云雷;鎳基高溫合金激光再制造零件結(jié)合區(qū)組織研究與性能控制[D];南京航空航天大學;2013年

2 潘滸;基于激光再制造的鎳基高溫合金成形質(zhì)量可控性基礎(chǔ)研究[D];南京航空航天大學;2013年

3 方坤;隨焊電磁感應(yīng)加熱控制焊接冷裂紋研究[D];哈爾濱工業(yè)大學;2010年

4 劉騰;高頻率脈沖固體激光深雕刻技術(shù)研究[D];北京工業(yè)大學;2009年

5 蘆亞萍;振動消除殘余應(yīng)力機理分析及試驗研究[D];浙江大學;2002年

，

本文編號：2401293