热处理对Ni-P镀层结构及硬度的影响

Effect of Heat Treatment on the Structure and Hardness of the Electroless Ni-P Deposits

采用化学镀的方法,在低碳钢基体上制备了纳米相含量不同的镀层。镀层在氩气保护下,分别经200,400℃保温1h进行热处理。采用电子探针(EPMA)、XRD射线衍射以及维氏硬度计研究了镀层热处理前后结构及硬度的变化。结果表明,随着纳米相含量的增多,镀层由非晶逐渐变为纳米晶,而硬度相应变大。200℃保温1h热处理,非晶与混晶镀层由于少量析出物Ni3P的出现使得硬度增大,而纳米晶镀层由于发生了弛豫使得镀层硬度降低。400℃保温1h热处理时,试样均发生了晶化,析出弥撒的Ni3P金属间化合物以及Ni相,纳米晶镀层的Ni相峰值强度增大最多,而非晶镀层所对应的Ni相峰值强度增大较少。然而,经400℃保温1h热处理后,非晶镀层硬度增大最多,这归因于非晶镀层析出的Ni3P金属间化合物数量多于混晶以及纳米晶镀层。

The deposits of electroless Ni-P with different nanocrystalline phase were prepared by electroless plating on mild steel substrate.The deposits were heat treated at 200℃ and 400℃ for 1h in an argon atmosphere,respectively.The effects of the heat treatment on the structure and hardness of the deposits were investigated and compared against the properties of the as-deposited samples by means of EPMA,XRD,hardness tester.The experimental results showed that the Ni-P deposits changed from amorphous to nanocrystalline with the increasing of nanocrystalline phase,thus increased the hardness of the deposits.The hardness of the amorphous and the co-existence became increased due to the precipitation of Ni3P at 200℃ heat treatment.The hardness of nanocrystalline deposit became decreased as the results of relaxation when being heat treated at 200℃ for 1h.The hardness of the deposits increased considerably due to the precipitation of dispersed hard Ni3P intermetallic compounds and nickel phase in the nickel matrix when being heat treated at 400℃ for 1h.The diffraction peaks strength of nanocrystalline in the XRD pattern had greater increase than that of the amorphous and the co-existence.However,the hardness of amorphous deposit increased greatly as the result of the amorphous deposit had more precipitation of Ni3P than that of nanocrystalline and the co-existence.