直流电场对固体软氮化的影响与作用机理分析

INFLUENCE OF DIRECT CURRENT FIELD ON POWDERPACK NITROCARBURIZING AND MECHANISM ANALYSIS

以45钢和20CrMnMo钢为例进行了直流电场下的固体软氮化.软氮化试样为直流电场负极,电场正极为板状,平行于试样的欲软氮化面放置.实验结果表明:直流电场加速软氮化过程,改善渗层硬度梯度分布;直流电场的加热作用加速渗剂的化学反应,提高N、C原子在试样中的扩散速度;与常规加热固体软氮化工艺相比,效率提高.分析认为:直流电场使含N、C活性基团向负极试样快速定向扩散,使得负极试样周围N、C浓度较常规粉末渗中的单纯热扩散提高,相对减少了渗箱内壁与样品非工作面对N、C原子的吸收;直流电场的物理作用强化渗剂间的化学反应,从而增加活性N、C原子或含N、C活性基团的产率与活性.

Powder-pack nitrocarburizing with direct current field （DCF） was carried out on steel 45 and steel 20CrMnMo. The treated specimen was taken as cathode and paralleled with plate anode. The test results indicate that DCF can enhance nitrocarburizing and modify hardness distribution profile along the case depth. The heating effect of DCF enhanced chemical reactions in the agent and accelerated the diffusions of nitrogen and carbon atoms in the specimen. Treating efficiency is improved compared with the conventional powder-pack nitrocarburizing （CPN） process, which is attributed to DCF increased obviously the concentrations of nitrogen and carbon at and around the cathode, accelerated diffusion of the nitrogen/carbon-containing species toward the cathode, while decreased the absorption of nitrogen/carbon atoms by inner wall of the pack box and the non-working surface of the specimen. In addition, DCF＇s physical effect of enhancing chemical reaction in the agent increased also the productivity and activity of nitrogen/carbon-containing species. KEY WORDS steel, powder-pack nitrocarburizing, direct current field, diffusion treating, energy-saving