氩气保护镍基复合镀层中增强相热稳定性研究

Investigation of Heat Stability of the Enhancement Phase in Ni-B_4C Electrocomposite under Argon Protection

研究了Ｎｉ－Ｂ４Ｃ复合镀层中，增强相Ｂ４Ｃ颗粒的热稳定性及镀层组成和性能的相应变化。金相显微结果表明，Ｂ４Ｃ颗粒在５００℃时开始分解，至８００℃分解完毕。Ｘ－ｒａｙ衍射、ＸＰＳ试验证实Ｂ４Ｃ颗粒分解后与Ｎｉ生成新相Ｎｉ３Ｂ，而且，由于Ｂ元素有着向镀层表面聚集的趋势，导致Ｎｉ３Ｂ首先在邻近表面的镀层中出现。Ｂ４Ｃ颗粒的分解，极大地降低镀层的硬度，但能有效地提高镀层的抗氧化能力。因此，Ｎｉ－Ｂ４Ｃ若作为耐磨材料，使用温度不宜大于５００℃，倘若利用它的抗氧化能力，即使在８００℃高温下，仍能耐受相当长的时间。

Both the heat stability of enhancement phase B4C particles and the relevant changes of compositions and features of the Ni-B4C electrocomposite are studied. Metallographic observation test shows that B4C particles begin to dissociate at 500 ℃, and the dissociation is over at 800 ℃. X-ray and XPS tests discover that the dissociative matters of B4C particles form Ni3B with Ni. The new phase Ni3B gathers at the inner surface of the coating because of the diffusive trend of B towards the surface. The dissocition of B.C particles greatly reduce the hardiness of the coating, but could effectively increase the antioxidzed ability.If Ni-B4C is used as wear-resisting materials,the working temperature should not exceed 500℃, however if its oxidation resistance is utilized the coating can last quite a long time even at the temperature as high as 800℃.