Ni-P electroformed layers were investigated for developing a steam generator tube repair technology in PWRs. The effects of an additive, RPP (Reagent over Pitting Protection) and agitation on mechanical properties and microstructure of the layer were evaluated. The addition of the RPP showed to inhibit the formation of pores, to refine the grain size, and to increase the residual stress in the layer. However, the agitation of the solution during electroforming was observed to increase pores in local regions of the electroformed layer, resulting in decreasing its mechanical properties. The heat treatment of the layer at $343^{circ}C$ for 1 hr. precipitated the very fine particles of Ni3P in the layer, which inhibited grain growth and increased microhardness.