STRUCTURE AND PROPERTIES OF ELECTROLESS NI DEPOSITS

The changes in structure and the hardness of two electroless deposited Ni-P alloy coatings (with P content of 1.5 and 9.5 wt pet) with heat treatment have been studied by XRD and TEM. The deposits containing 1. 5 wt pet P can be represented as an fee NiP supersaturated solid solut ion of 5 similar to 10 nm microcrystallites, whereas the deposits cont aining 9.5 wt pet P are amorphous. The heat treatment process induces crystallization of amorphous Ni to Ni phosphides and fee Ni. Both of t he deposits reach maximum hardness after annealing at 400 degrees C fo r 1 h. All coated steel specimens are inferior in fatigue strength to uncoated steel specimens mainly due to the poor fatigue resistance of the coating itself.