Studies on electroless nickel boride coating on boron carbide particles

摘要

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 phi, 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_2B, Ni_3B and Ni_4B_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_2B to stable crystalline Ni_3B phase. The NiB coated particle shows lower particle-matrix interfacial reaction, better wettability and enhanced dispersion in aluminium composites compared to uncoated particles.