Microstructure and properties of 40CrNiMo steel corner area boronized layer prepared by alternating current electric field assisted pack boriding
A modified powder with Al2O3 as the filler and activated carbon as the additive was used as the boronizing agent,40CrNiMo steel was used as the matrix,and electric field enhancement assisted solid boriding was carried out at 630,650,700,750 and 850 ℃ under the action of a 75 V/100 Hz alternating current(AC)electric field.Microscopic analysis and performance testing were conducted on the boronized samples using X-ray diffraction,scanning electron microscopy and hardness tester.The results show that the AC electric field has a significant promoting effect on the boriding process,and even at lower boriding temperatures(750℃,700 ℃ and 650℃),a single Fe2B phase boriding layer can be formed in the planar and corner areas of the 40CrNiMo steel sample.At 850 ℃,a small amount of FeB phase appears at the corners of the boronized layer.Excessive temperature(such as 850 ℃)and electric field assisted boriding current(such as 2.38 A current at 700 ℃)can cause the formation of a loose surface layer on the surface of the boronized layer,which is not conducive to the formation of a dense boronized layer.The boronized layer after 4 h of boriding at 750℃has the highest compactness and hardness,with the boronized layer thickness and surface hardness of 120 μm and 1700 HVO.05,respectively.
40CrNiMo steelpowder boridingFe2Bcorner area boridingalternating current electric field
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