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, Ni2B, Ni3B and Ni4B3. An effective Ni-B alloy coating with better surface characteristics was formed at pH 8 under 75 degrees 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 degrees C showed remarkable Ni-B phase transformation from metastable NiB and Ni2B to stable crystalline Ni3B phase. The NiB coated particle shows lower particle-matrix interfacial reaction, better wettability and enhanced dispersion in aluminium composites compared to uncoated particles.