表面纳米化过程中18CrNiMo7-6钢的软化与硬化
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摘要
对淬火后低温回火的18CrNiMo7-6钢采用旋转加速喷丸技术进行表面纳米化处理,研究了18CrNiMo7-6钢纳米化过程中的软化和硬化现象。结果表明:经旋转加速喷丸处理后,钢的拉伸性能轻微提升。样品厚度方向上不同深度位置同时出现了硬化与软化现象,其中,心部和最表层硬度都有所增加,而样品次表层硬度却较喷丸前轻微降低,从而使得样品的显微硬度在厚度方向上呈现"W"型分布。在对样品喷丸前后不同深度位置的微观组织表征后发现,材料次表面的软化现象与该位置发生的动态回复有关;而心部和最表层虽然都发生硬化,其强化机制也不尽相同。
Rotationally accelerated shot peening( RASP) treatment was applied to a quenched and low-temperature-tempered 18CrNiMo7-6steel for surface nanocrystallization,then softening and hardening of the steel during surface nanocrystallization were studied. The results show that the tensile strength of the samples after RASP is slightly improved. The microhardness test reveals that hardening and softening occur simultaneously at different depths in the cross-section of samples after RASP. Specifically,the superficial and central parts of samples are hardened while the subsurface softened,resulting a "W" shaped distribution of cross-sectional microhardness. Characterization of microstructures at different depths through the thickness direction of samples before and after RASP treatment shows that the softening occurring in the subsurface is attributed to dynamic recovery,while the hardening in the superficial and the central parts is caused by different mechanisms.
Rotationally accelerated shot peening( RASP) treatment was applied to a quenched and low-temperature-tempered 18CrNiMo7-6steel for surface nanocrystallization,then softening and hardening of the steel during surface nanocrystallization were studied. The results show that the tensile strength of the samples after RASP is slightly improved. The microhardness test reveals that hardening and softening occur simultaneously at different depths in the cross-section of samples after RASP. Specifically,the superficial and central parts of samples are hardened while the subsurface softened,resulting a "W" shaped distribution of cross-sectional microhardness. Characterization of microstructures at different depths through the thickness direction of samples before and after RASP treatment shows that the softening occurring in the subsurface is attributed to dynamic recovery,while the hardening in the superficial and the central parts is caused by different mechanisms.
引文
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[2]牛娜,卫英慧,林万明,等.表面机械研磨处理对Cu-4Ti合金组织及力学性能的影响[J].金属热处理,2012,37(8):46-49.Niu Na,Wei Yinghui,Lin Wanming,et al.Microstructure and mechanical properties of nano-crystalline surface layer in Cu-4Ti alloy induced by surface mechanical attrition treatment[J].Heat Treatment of Metals,2012,37(8):46-49.
[3]杨新诚,王伟,蔡宝壮,等.不同温度下表面机械研磨对纯铜组织及性能的影响[J].金属热处理,2016,41(1):195-198.Yang Xincheng,Wang wei,Cai Baozhuang,et al.Effect of surface mechanical attrition treatment on microstructure and properties of pure copper at different temperatures[J].Heat Treatment of Metals,2016,41(1):195-198.
[4]Huang H W,Wang Z B,Lu J,et al.Fatigue behaviors of AISI 316Lstainless steel with a gradient nanostructured surface layer[J].Acta Materialia,2015,87:150-160.
[5]孙建春,盛光敏,王越田,等.高能喷丸法实现工业纯铁表面自纳米化[J].金属热处理,2010,35(5):38-41.Sun Jianchun,Sheng Guangmin,Wang Yuetian,et al.Surface selfnanocrystallization on industrial pure iron by high energy shot peening[J].Heat Treatment of Metals,2010,35(5):38-41.
[6]Fu P,Zhan K,Jiang C.Micro-structure and surface layer properties of18CrNiMo7-6 steel after multistep shot peening[J].Materials and Design,2013,51(5):309-314.
[7]LüY H,Gai D Y,Song Y Q,et al.Effect of carburizing and shot peening on the microstructure and surface properties of 17-CrNi6-Mo steel[J].Strength of Materials,2015,47(1):47-55.
[8]Liu G,Lu J,Lu K.Surface nanocrystallization of 316L stainless steel induced by ultrasonic shot peening[J].Materials Science and Engineering A,2000,286(1):91-95.
[9]Zhou L,Long C,He W,et al.Improvement of high-temperature fatigue performance in the nickel-based alloy by LSP-induced surface nanocrystallization[J].Journal of Alloys and Compounds,2018,744:156-164.
[10]许久凌,黄海威,赵明纯,等.316L不锈钢在表面机械滚压处理时的形变诱导马氏体相变和组织细化过程[J].材料研究学报,2016(1):15-22.Xu Jiuling,Huang Haiwei,Zhao Mingchun,et al.Processes of deformation-induced martensite transformation and microstructure refinement of 316L stainless steel during surface mechanical rolling treatment[J].Chinese Journal of Materials Research,2016(1):15-22.
[11]He Q Y,Zhu M,Mei Q S,et al.Microstructural and hardness gradients in Cu processed by high pressure surface rolling[J].IOPConference Series:Materials Science and Engineering,2017,219(1):012025.
[12]Wang X,Li Y S,Zhang Q,et al.Gradient structured copper by rotationally accelerated shot peening[J].Journal of Materials Science and Technology,2017,33(7):758-761.
[13]Zhang Y S,Wei Q M,Niu H Z,et al.Formation of nanocrystalline structure in tantalum by sliding friction treatment[J].International Journal of Refractory Metals and Hard Materials,2014,45:71-75.
[14]Liu Q,Huang X,Lloyd D J,et al.Microstructure and strength of commercial purity aluminium(AA 1200)cold-rolled to large strains[J].Acta Materialia,2002,50(15):3789-3802.
[15]Kamikawa N,Tsuji N,Huang X,et al.Through-thickness characterization of microstructure and texture in high purity aluminum processed to high strain by accumulative roll-bonding[J].Materials Transactions,2007,48(8):1978-1985.
[16]Huges D A,Hansen N.Microstructure and strength of nickel at large strains[J].Acta Materialia,2000,48(11):2985-3004.
[17]Li B L,Godfrey A,Meng Q C,et al.Microstructural evolution of IF-steel during cold rolling[J].Acta Materialia,2004,52(4):1069-1081.
[18]Kamikawa N,Huang X,Tsuji N,et al.Strengthening mechanisms in nanostructured high-purity aluminium deformed to high strain and annealed[J].Acta Materialia,2009,57(14):4198-4208.
[19]Yao B,Han Z,Lu K.Dry sliding tribological properties and subsurface structure of nanostructured copper at liquid nitrogen temperature[J].Wear,2013,301(1/2):608-614.
[20]Chen X,Han Z,Lu K.Wear mechanism transition dominated by subsurface recrystallization structure in Cu-Al alloys[J].Wear,2014,320(1/2):41-50.
[21]Chen X,Han Z,Li X,et al.Lowering coefficient of friction in Cu alloys with stable gradient nanostructures[J].Science Advances,2016,2(12):e1601942.