Studies on electroless nickel boride coating on boron carbide particles

Ni-B alloy deposits were successfully formed over alkali surface treated boron carbide by electroless technique and the effects of processing parameters such as reduction bath pH, temperature and post-heat treatment were investigated. Microstructural studies show remarkable changes in structural morphology from mesh-like structure to platelet type Ni-B coating. The main Ni-B phases observed were NiB, Ni 2 B, Ni 3 B and Ni 4 B 3 . An effective Ni-B alloy coating with better surface characteristics was formed at pH 8 under 75°C reaction bath temperature in the presence of bath stabiliser. The post-heat treatment of Ni-B coated particles under varying bath reaction temperatures at 400°C showed remarkable Ni-B phase transformation from metastable NiB and Ni 2 B to stable crystalline Ni 3 B phase. The NiB coated particle shows lower particle-matrix interfacial reaction, better wettability and enhanced dispersion in aluminium composites compared to uncoated particles.