Characteristics and mechanisms of accelerating pack boriding by direct current field at low and moderate temperatures

Direct current field (DCF) was employed in pack boriding at low and moderate temperatures. Samples were arranged in different positions in a sealed pack boriding container for studying characteristics of the DCF assisted pack boriding and mechanisms of accelerating pack boriding by DCF. The test results revealed that DCF enhanced pack boriding not only to samples as cathode but also to samples located between the cathode and anode. The extent of the enhancement varied with the location of the sample. The strongest enhancement was achieved on the cathode sampleʹs side facing the anode. It is proposed that the DCFʹs physical effect of enhancing chemical reactions in the agent increases the activity and productivity of boron-containing species. The DCF makes the concentrations of active boron-containing species at and around the sample as cathode much higher than in any other position by forcing boron-containing species to diffuse fast toward the cathode. The electrically induced boron migration in the sample by DCF leads a faster growth of boriding case at the sampleʹs side facing the anode. The DCFʹs electromagnetic effect might be helpful for forming more vacancies in the sample, which favors boronʹs diffusion in the substrate.