Effects And Mechanisms Of Electric Fields On Pack Cementations

Metal parts’ wear resistance, corrosion resistance and anti-oxidationability can be improved by pack cementations, among which pack boriding,aluminizing and chromizing are commonly employed. Those packcementations have many advantages, which include good surface quality ofthe treated component, easy handling, less demand to treating facilities andbeing suitable for treating parts with complex shape. However, thoseconventional technologies have shortcomings of high processing temperature,long process duration, high-energy consuming and low-efficiency in utilizingmedium to reach a case with an effective thickness.Researches were carried out with self-designed apparatus by applyingappropriate electric field, which includes direct current field (DCF) andalternating current field (ACF), on pack boriding, chromizing and aluminizing.Investigations were taken on the effects of the different parameters of theelectric field (including the distribution, voltage and current) on thecharacteristics of the treated cases’ formation and the diffusion of the requiredatoms at different temperatures by different soaking time and with differentagents. Optical microscopy, X ray diffraction and microhardness testing wereemployed for analyzing the structure, phases and hardness of the treated cases,respectively. The mechanisms of the electric fields’ function on thecementations were proposed based on the obtained test results.The results showed that proper DCF and ACF enhanced the formation ofthe cases of pack boriding, chromizing and aluminizing carried out at low andmoderate temperatures, although the extent of which was influenced by manyfactors. The DCF and ACF also improve the treated cases’ structure andproperties. The treating temperature can be lowered, the soaking time can beshortened, and the utilization ratio of agents can be increased in the electricfield enhanced cementations.It was proposed that electric field could enhance the chemical reactionsin the powder agent, leading more required active atoms or radicalscontaining required atoms formed. The electric field could promote oroptimizing diffusions of the required active atoms or radicals in the packcontainer and the diffusion of atoms in the treated specimens.