無電解Ni-Pメッキ皮膜の熱処理による相変化

抄録

It is well known that the hardness of electroless Ni-P deposit remarkably increases after heating at about 400°C. However, the knowledge of the above mechanism has scarcely been reported.
In these experiments, the metallographical phase changes of electroless Ni-P deposit were investigated by thermal and crystallographical analyses in comparison with the corresponding changes of Ni-P powder compacts.
The results obtained were as follows:
(1) In the curves for thermal analysis of electroless Ni-P deposit and Ni-P compact, endothermic and exothermic changes could be observed.
(2) Judging from the X-ray diffraction patterns for both electroless Ni-P deposit and powder compact, it was possible to confirm that nickel phosphide had been formed at the temperature of the exothermic change. It could be explained that the exothermic changes would be attributed to the heat of formation of nickel phosphide.
Consequently, it was concluded that the Ni-P deposit would be the mixture of Ni and P, and the remarkable increase of hardness would be due to the formation of nickel phosphide.
(3) It was considered that the endothermic changes would be the heat of vaporization of yellow phosphorus in Ni-P deposit or the heat of sublimation of red phosphorus in Ni-P powder compact.