Electroless Ni-P/Ni-B-B4C duplex composite coatings for improving the corrosion and tribological behavior of Ck45 steel

Ni-P/Ni-B-B4C duplex composite coatings were deposited on Ck45 by electroless plating process, and their structure, morphology, micro hardness and corrosion resistance were evaluated. The duplex coatings were prepared using dual baths (acidic hypophosphite- and alkaline borohydride-reduced electroless nickel baths) with Ni-P as the inner layer. The coatings were amorphous in as-plated condition and nanocrystallized, and produced nickel borides upon heat-treatment. SEM observations showed that the duplex interface on the Ck45 was uniform, and the compatibility between the layers was good. The Ni-P/Ni-B-B4C coating’s microhardness and corrosion resistance of Ni-B-B4C coating as the outer layer were higher than Ni-P coatings. The Ni-P/Ni-B-B4C duplex composite coatings with high hardness and good corrosion resistance properties would expand their scope of applications.