Effect of boron on the microstructure and physical properties of chemically vapour deposited nickel films

Article abstract of DOI:10.1007/BF01106834

The solid solution addition of boron greatly enhances the strength and hardness of chemically vapor deposited (CVD) nickel while dramatically changing the microstructures. The solid solubility of boron in nickel is limited, and single-phase alloys containing in excess of 0.3 at% B are supersaturated with respect to the formation of one or more intermetallic boride phases. Single-phase Ni-B alloys containing 0 to 13.0 at% B were produced by CVD on polycrystalline copper substrates at 155°C in an atmospheric pressure process. The microstructure, mechanical and physical properties were characterized for the alloys both as-deposited and after various thermal treatments by using optical microscopy, transmission electron microscopy, X-ray diffraction and micro-indentation hardness testing with a diamond pyramid indentor. The grain size of the alloys was found to decrease sharply with rising boron content. Coneomitantly, the defect density of the material rose significantly, the microhardness increased and the ductility decreased. With annealing at a temperature of 300°C or greater, precipitation of the Ni₃B intermetallic phase, recovery and grain growth occurred.