Effect of Surface Structure and Hydrogen on the Fatigue Strength of Electroless Nickel-Phosphorus Plated Al-1.2%Si Alloy

In this study, we examined the influence of surface precipitates and hydrogen gas on the fatigue strength of an electroless Ni-P plated Al-1.2%Si alloy. As the results, the following points were clarified. (1) Fatigue strength of the specimen subjected to zincate treatment only after a furnace cooling treatment was almost the same as only furnace cooling. (2) Fatigue strength of the specimen subjected to Ni-P plating after a furnace cooling treatment was reduced overall, except for the high-stress region, rather than one of the non-processed materials. (3) Fatigue strength of the specimen subjected to Ni-P plating after aging treatment showed a clear increase in comparison to one of the non-processed materials. (4) In the specimens subjected to the Ni-P plating after a furnace cooling treatment or aging treatment, clear hydrogen desorption was recognized. On the other hand, there was only hydrogen desorption from a few of the specimens subjected to zincate treatment after the furnace cooling treatment or only furnace cooling. It is considered that the poor fatigue strengths of the plating materials are mainly due to the interaction between the surface precipitates and hydrogen gas.