超声表面滚压纳米化技术研究现状

Research Status of USRP Nanocrystallization Technology

传统表面纳米化多采用机械处理法,利用剧烈的塑性变形(SPD)使材料表面生成高强度、高硬度的纳米层,但其表面粗糙度高且存在严重集中的应力变形。超声表面滚压(USRP)纳米技术中,滚压头按照预定路线处理材料表面,能同时改善表面粗糙度和强度、硬度。介绍了USRP表面纳米化工艺机理和工艺参数。USRP引起晶体缺陷反复湮灭与再生,高位错能材料以“位错分割”方法细化晶粒至纳米量级。结合国内外现状,联合晶粒细化机理分析USRP处理前后材料性能的变化,包括表面粗糙度和残余应力、扩散性能、耐腐蚀性能、抗疲劳性能和耐磨损性能。综合阐述了USRP复合工艺对材料性能的影响,包括等离子氮化(PN)、高能离子注渗技术(HEII)、加热辅助等。剧烈塑形可增加材料表面活性,加速渗氮反应进行;USRP+HEII处理后,高转速下未出现疲劳磨损,材料的耐磨性能和疲劳性能提高;加热辅助USRP可实现晶粒细化和应变强化;Al2O3粉末结合USRP可实现表面纳米化和高硬度Al2O3薄膜。最后对USRP技术进行了展望,可深入研究中低层错能纳米化机理,强化USRP工艺标准研究,加快USRP复合工艺的发展。

The traditional surface nanocrystallization mostly adopt mechanical treatment,which generates nanometer layers with high strength and hardness on the material surface by severe plastic deformation(SPD),but the surface roughness is high and there is serious concentrated stress deformation.In ultrasonic surface rolling(USRP)nanotechnology,the rolling head processes the material surface according to the predetermined route,and at the same time changes the surface roughness and strength hardness.The mechanism and parameters of USRP surface nanofilization process are introduced.USRP causes repeated annihilation and regeneration of crystal defects,high level fault energy materials can be refined to nanometer size by“dislocation segmentation”method.According to the domestic and international situation,before and after USRP treatment the changes of material properties are analyzed by combining with grain refinement mechanism,including surface roughness and residual stress,diffusion property,corrosion resistance,fatigue resistance and wear resistance.The effects of USRP composite process on the material properties are comprehensively described,including plasma nitriding(PN),high-energy ion injection and infiltration(HEII),heating assistance,etc.The severe SPD increases the material surface activity and accelerates the nitriding reaction.After USRP+HEII treatment,there is no fatigue wear at high rotation speed,and the wear resistance and fatigue performance were improved.Heating assisted USRP to achieve grain refinement and strain strengthening.The surface nanometer and high hardness Al2O3 film were realized simultaneously by Al2O3 powder combined with USRP.The mechanism of middle and low level fault-energy nanorization is deeply studied,and study on strengthening USRP process standard to enhance the development of USRP composite process.