The influence of thermal treatments on the adhesion of electrolessly deposited Ni(P) layers on alumina ceramic

The adhesion of electrolessly deposited Ni(P) on Al2O3 was studied as a function of annealing temperature up to 580 C. The interfacial structure was analysed by electron microscopy. The optimum annealing temperature was 400 C, where peel energy and adhesion strength increased to two to three times the values as-deposited. The weak boundary layer found in the as-deposited layer was still present after annealing, and the fracture path was through this interfacial layer. The improvement in adhesion was attributed to stronger cohesion of material in the weak boundary layer. 15 refs.