| The electrolytic boronizing on low carbon steel was conducted at 700-900℃ for 2 hours under the current density of 0.5A/㎠ using various contents of KCl-LiCl in the fused salt of Na₂B₄,O_γKCl-LiCl. The KCl·LiCl compound has the eutectic composition (54wt.%KCl and 46wt%LiCl). The effect of the additives such as Al or B₄C into the 4Na₂B₄O_7·KCl·LiCl(weight ratio) on the formation of boronized layer was investigated. The boronized layers were composed of two sublayers, i. e., FeB and Fe₂B, which have tooth structure. The electrolytic boronizing on medium carbon steel SM45C and stainless steel STS304 was also conducted at 800-950℃ for 1-6 hours under the current density of 0.5A/㎠ in the electrolyte of 4(Na₂B₄O_7·Al)·KCl LiCl. In this electrolyte, the average boronized layer thicknesses of the low carbon steel, SM45C and STS304 at 800℃ for 2 hours were 70, 47 and 15 ㎛, respectively. The thickness of the two sublayers was significantly increased with increasing boronizing temperature. To obtain a single Fe₂B layer without FeB sublayer, the boronized low carbon steels were homogenized at 900℃ for 2 hours and the boronized SM45C and STS304 were homogenized at 950℃ for 4 hours. It was found that the single layer with the microhardness of Hv=1300 was formed. |
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