A novel rapid D.C. salt bath nitrocarburizing technology

• A salt bath nitrocarburizing technology enhanced by D. C. electric field was developed primarily.
• D. C. electric field had a significant enhancement effect on salt bath nitrocarburizing.
• The heating duration could be shortened to less than a half by applying appropriate D. C. electric field.
• D. C. electric field could force active atoms diffuse directionally toward the treated specimen.

A novel rapid salt bath nitrocarburizing technology was primarily developed by additionally applying direct current (D. C.) electric field on the basis of traditional technique (NM). The results showed that D. C. electric field could significantly enhance the nitrocarburizing efficiency, shorten the holding time and decrease the treating temperature comparing with the NM. To get a composite layer thickness of 18 μm at treating temperature of 575 °C, the holding time was shortened from 100 min in NM to less than a half by additionally applying 7.5 V D.C., and the thickness was increased from 18.0 μm up to 29 μm at the same holding duration of 100 min. And it was found that the enhancement effect was closely related to the voltage of D. C. electric field, voltage higher than 3 V was necessary to get obvious enhancement effect. The main enhancement mechanism was analysized as well.