阴极电压和供氮方式对纯氮离子渗氮的影响

分别研究了在500、600、650和700 V阴极电压条件下采用连续供气抽真空和间歇供氮闭炉的方式进行纯氮离子渗氮的工艺及机理.通过对间歇供氮闭炉离子渗氮层显微组织、相组成和硬度梯度的测定与分析,计算和验证了该工艺中N2分子临界离解能.结果表明,纯氮离子渗氮的活性氮原子来自于经阴极位降区加速的高能N 2与中性N2分子间的非弹性碰撞,离解N2分子的N 2离子临界能为48.64 eV,相应的阴极电压门槛值为650 V.纯氮离子渗氮工艺除要求阴极电压高于650 V外,间歇供气闭炉渗氮也是必备条件,在一定温度和足够高的阴极电压下,只有采用间歇供氮闭炉方式进行离子渗氮,从N2分子才能离解出足够多的活性氮原子,使试样表面产生明显的渗氮效果.

Influence of Cathode Voltage and Nitrogen Supply Way on Ion Nitriding with Pure Nitrogen

The process and mechanism of ion nitriding with pure nitrogen were studied by way of continuous nitrogen supply simultaneously with vacuum pumping and furnace shutdown after intermittent nitrogen supply,respectively,under cathode voltage of 500,600,650 and 700 V.The critical dissociation energy of nitrogen molecules for ion nitriding with pure nitrogen was calculated and verified by measuring and analyzing the microstructure,phase composition and hardness gradient of nitrided layers.The results show that the active nitrogen atoms of ion nitriding with pure nitrogen mainly result from the non-elastically collision between the positive ions N 2 and the neutral nitrogen molecules N2.The N 2 ion critical energy of dissociating neutral N2 molecules is 48.64 eV and its corresponding cathode voltage threshold value is 650 V.For ion nitriding with pure nitrogen,the furnace shutdown ion nitriding after intermittent nitrogen supply is necessary in addition to that the cathode voltage is required to exceed 650 V.Under fixed temperature and enough high cathode voltage,only the ion nitriding by way of the furnace shutdown after intermittent nitrogen supply can make N2 molecules dissociate enough active nitrogen atoms to form nitriding layers and make sample surface produce obvious nitriding effect.