n-Al2O3/Ni复合电刷镀层的接触疲劳行为

为研究纳米颗粒复合电刷镀层的接触疲劳行为,通过在镍盐溶液中加入纳米氧化铝(n-Al2O3)颗粒,采用电刷镀技术制备了含n-Al2O3颗粒的镍基复合镀层(n-Al2O3/Ni),采用接触疲劳试验机评价了镀态和热处理态的n-Al2O3/Ni复合镀层的抗接触疲劳性能,并与纯镍刷镀层进行了性能对比.借助SEM和TEM对复合刷镀层的组织进行了分析,探讨了复合刷镀层的接触疲劳失效过程以及纳米颗粒等对刷镀层疲劳失效过程的影响.研究表明:n-Al2O3/Ni复合镀层在镀态下的接触疲劳寿命超过100万周次,明显高于纯镍镀层;退火后n-Al2O3/Ni复合镀层接触疲劳寿命为45.9万次,为纯镍镀层的1.62倍;复合镀层的接触疲劳失效过程分为裂纹萌生、裂纹扩展和镀层断裂3个阶段;纳米颗粒在复合镀层接触疲劳失效过程中起到阻碍位错滑移的作用,从而抑制塑性变形和裂纹扩展,使复合镀层具有较高的接触疲劳寿命.

Contact fatigue behaviors of brush electroplated n- Al2O3/Ni composite coating

In order to investigate contact fatigue behaviors of brush electroplated metal matrix nanocomposite coatings,nano scale alumina particle reinforced nickel matrix composite(n-Al_2O_3/Ni) coating was prepared by brush electroplating process from nickel salt solution containing n-Al_2O_3 particles.A contact-fatigue tester was employed to access contact fatigue life of the as-plated and heat-treated composite coatings while comparing with that of the brush plated Ni coating.With microstructure observation of the composite coating,contact fatigue failure process and effects of nanoparticles on the process were investigated.The results showed that contact fatigue life of the n-Al_2O_3/Ni composite coating was over one million cycles,which was much higher than that of the Ni coating.When the coatings were annealed,the contact fatigue life of the n-Al_2O_3/Ni coating was 1.62 times of that of the Ni coating.As for the n-Al_2O_3/Ni coating,analysis showed the contact fatigue failure process was composed of three stages,such as crack initiating,crack propagating and coating rupturing.TEM observation of the contact fatigue deformation layer showed that during contact fatigue of the composite coating,nanoparticles hindered the slippage of dislocations and restrained the plastic deformation and crack propagation,which resulted in higher contact fatigue life of the composite coating.