镍铬合金选区激光熔化成形非水平悬垂结构的工艺策略试验研究
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摘要
非水平悬垂结构是选区激光熔化(SLM)成形复杂零件中较为典型的结构,其成形缺陷如翘曲变形、悬垂物、挂渣等较多,故研究悬垂结构选区激光熔化(SLM)成形中的工艺缺陷,改变和优化工艺策略,提高悬垂结构打印的精度和质量,对SLM技术的大规模推广和应用具有积极的作用。研究了选区激光熔化成形试验中,在极限成形角度附近,不同激光功率(100, 150, 200 W)和不同扫描策略如线扫描、棋盘扫描、条形扫描策略下,镍铬合金钢成形悬垂结构的精度和表面质量。根据不同策略的比较结果,提出了"回"字形完全填充扫描策略,并进行了试验验证。试验表明:镍铬合金钢在极限成形角度附近成形的悬垂结构,能够保证良好的成形精度和工艺效果,基本避免了翘曲、悬垂物等缺陷的产生。比较明显的成形缺陷有表面未熔缺陷和上下悬垂面挂渣缺陷,这些缺陷严重影响了表面粗糙度和成形精度,采用缩小点距、线间距的"回"字形完全填充扫描策略可获得最低的表面粗糙度值和较好的成形效果。
Non-horizontal overhanging structure is a typical structure of complex parts formed by selective laser melting(SLM). There are many forming defects such as warping deformation, overhang and slag hanging. Therefore, the study of defects in SLM forming of overhanging structure, the change and optimization of technological strategies, and the improvement of forming accuracy and quality of overhanging structure have a positive effect on the large-scale popularization and application of SLM technology. In the selective laser melting forming experiment, the accuracy and surface quality of nicochrome steel forming overhanging structure near the limit forming angle were studied with different laser powers(100, 150, 200 W) and scanning strategies such as Meander, Chessboard, Stripe. According to the comparison results, the fully filled scanning strategy with homocentric squares was proposed and verified. The experiment showed that the overhanging structure formed by the nicochrome steel near the extreme forming angle could ensure good forming precision and process effect, and basically avoid the occurrence of defects such as warping deformation and overhanging. The more obvious forming defects were surface unmelted defects and slag on the upper and underside overhanging surfaces. These defects seriously affected the surface roughness and forming accuracy. The fully filled scanning strategy with homocentric squares which reduced point distance and hatch space could achieve the lowest surface roughness value and had a better forming quality.
Non-horizontal overhanging structure is a typical structure of complex parts formed by selective laser melting(SLM). There are many forming defects such as warping deformation, overhang and slag hanging. Therefore, the study of defects in SLM forming of overhanging structure, the change and optimization of technological strategies, and the improvement of forming accuracy and quality of overhanging structure have a positive effect on the large-scale popularization and application of SLM technology. In the selective laser melting forming experiment, the accuracy and surface quality of nicochrome steel forming overhanging structure near the limit forming angle were studied with different laser powers(100, 150, 200 W) and scanning strategies such as Meander, Chessboard, Stripe. According to the comparison results, the fully filled scanning strategy with homocentric squares was proposed and verified. The experiment showed that the overhanging structure formed by the nicochrome steel near the extreme forming angle could ensure good forming precision and process effect, and basically avoid the occurrence of defects such as warping deformation and overhanging. The more obvious forming defects were surface unmelted defects and slag on the upper and underside overhanging surfaces. These defects seriously affected the surface roughness and forming accuracy. The fully filled scanning strategy with homocentric squares which reduced point distance and hatch space could achieve the lowest surface roughness value and had a better forming quality.
引文
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[15] Shi W T,Wang P,Liu Y D,Shi X Z.Experimental study on cracking mechanism and process optimization of selective laser melting TiAl alloy [J].Chinese Journal of Rare Metals,2019,43(4):349.(石文天,王朋,刘玉德,石学智.选区激光熔化TiAl合金裂纹产生机理及工艺优化试验研究 [J].稀有金属,2019,43(4):349.)
[2] Wang D,Mai S Z,Xiao D M,Yang Y Q.Surface quality of the curved overhanging structure manufactured from 316-L stainless steel by SLM [J].The International Journal of Advanced Manufacturing Technology,2015,1.
[3] Liu Y J,Li X P,Zhang L C,Sercombe T B.Processing and properties of topologically optimised biomedical Ti-24Nb-4Zr-8Sn scaffolds manufactured by selective laser melting [J].Mater.Sci.Eng.A,2015,642:268.
[4] Gu D D.Materials creation adds new dimensions to 3D printing [J].Sci.Bull.,2016,61:1718.
[5] Wu G L,Liu T T,Zhang C D,Liao W H.Quality study of suspension structure formed by Ti6Al4V laser selective melting [J].China Mechanical Engineering,2016,27(13):1810.(吴根丽,刘婷婷,张长东,廖文和.Ti6Al4V激光选区熔化成形悬垂结构的质量研究 [J].中国机械工程,2016,27(13):1810.)
[6] Lin H J,Shen L D,Jiang J H,Xie D Q,Liang H X,Fan Q C.Simulation analysis of characteristics of laser melting forming suspension structures in selected areas [J].Acta Aeronautica Sinica,2018,39(7):421897.(林会杰,沈理达,姜金辉,谢德巧,梁绘昕,范钦春.选区激光熔化成型悬垂结构特征模拟分析 [J].航空学报,2018,39(7):421897.)
[7] Duan S Q.Study on the quality of melting forming of laser selection in overhanging holes [J].China Laser,2018,45(4):0402007.(段声勤.悬垂圆孔激光选区熔化成形质量研究 [J].中国激光,2018,45(4):0402007.)
[8] Han Q Q,Gu H,Soe S,Setchi R,Lacan F,Hill J.Manufacturability of AlSi10Mg overhang structures fabricated by laser powder bed fusion [J].Materials & Design,2018,60:1080.
[9] Yasa E,Craeghs T,Badrossamay M,Kruth J P.Rapid manufacturing research at the catholic university of leuven [A].Proceedings of US-TURKEY Workshop on Rapid Technologies [C].Istanbul,Turkey,2009.1.
[10] Yang Y Q,Lu J B,Wang D,Luo Z Y.Research on non-horizontal drape surface of 316L stainless steel by selective laser melting [J].Materials Science and Technology,2011,19(6):94.(杨永强,卢建斌,王迪,罗子艺.316L不锈钢选区激光熔化成型非水平悬垂面研究 [J].材料科学与工艺,2011,19(6):94.)
[11] Hong J,Tang Y P,Lu B H,Wu D L.Study on the rules of supporting design for non-horizontal undersurface of parts in rapid prototyping by light curing [J].Journal of Mechanical Engineering,2004,40(8):155.(洪军,唐一平,卢秉恒,武殿梁.光固化快速成型中零件非水平下表面的支撑设计规则研究 [J].机械工程学报,2004,40(8):155.)
[12] Ma T.Research on Some Key Issues in Laser Selective Sintering Rapid Prototyping Technology [D].Zhenjiang:Jiangsu University,2003.28.(马涛.激光选区烧结快速成型技术中若干关键问题的研究 [D].镇江:江苏大学,2003.28.)
[13] Strano G,Hao L,Everson R M,Evans K E.Surface roughness analysis,modelling and prediction in selective laser melting [J].Journal of Materials Processing Technology,2013,213(4):589.
[14] Liu Z Y,Qian B,Li P,Zhang J R,Chi M,Li T F.SLM Real-time premelting/remelting new forming technology research [J].Mechanical Science and Technology,2019,38(4):566.(刘志远,钱波,李培,张剑睿,池敏,李腾飞.SLM实时预熔/重熔的新型成型工艺研究[J].机械科学与技术,2019,38(4):566.)
[15] Shi W T,Wang P,Liu Y D,Shi X Z.Experimental study on cracking mechanism and process optimization of selective laser melting TiAl alloy [J].Chinese Journal of Rare Metals,2019,43(4):349.(石文天,王朋,刘玉德,石学智.选区激光熔化TiAl合金裂纹产生机理及工艺优化试验研究 [J].稀有金属,2019,43(4):349.)