Using α-Al2O3 powder as boriding filler and 2％activated carbon as additive,the variation of boiiding current was investigated under a constant AC electric field assisted pack-boriding carried out on 40CrNiMo steel.By adjusting the AC electric field voltage to obtain stable low temperature boriding temperature,a borided layer was prepared on the surface of 40CrNiMo steel and characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM)and microhardness tester.The results show that a stable conductor is created as a result of activated carbon adhering to the Al2O3 powder's surface,which stabilizes the boriding current at different stages of the electric field assisted pack-boriding,resulting in a relatively stable boriding temperature.A dense single-phase Fe2B borided layer on the surface of 40CrNiMo steel can be prepared by adjusting the electric field voltage to control the actual boriding temperature at a lower temperature(650,680,700 ℃).The SEM observation shows that the thickness of the borided layer is ≥13 μm.The surface hardness of the borided layer is relatively high and can reach about 1200 HV0.05 even at 650℃.
variable electric fieldlow temperature boridinghardnessFe2B
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