Fabrication and characterization of corrosion resistant amorphous-nanocrystalline alloy Ni49Co3Mo22B26 by galvanostatic deposition

Amorphous materials have unique physical properties but have limited practical use due to their low ductility and thermal instability. A quaternary Ni49Co3Mo22B26 amorphous-nanocrystalline plating was prepared by electrodeposition to obtain good hardness, corrosion resistance, and thermal stability. Multiple electrolyte baths with boric acid concentration ranging from 0.3 M to 0.8 M were investigated to study the co-deposition pattern of molybdenum (Mo) and boron (B) with iron-group elements. Experimentations suggest that an array of binary, ternary, and quaternary alloys can be fabricated by adjusting boric acid concentration in an electrolyte bath. Energy Dispersive X-ray Spectroscopy (EDS) analysis shows that co-deposition of Mo requires sluggish mass transport of iron group element nickel (Ni) and cobalt (Co) and high boric acid concentration retards Mo deposition entirely. X-ray diffraction (XRD) patterns were examined to identify the formation of amorphousnanocrystalline film deposition. An average hardness for quaternary Ni-Co-Mo-B deposit samples was measured between the range of 380 HV- 450 HV, and the hardness increases with increased B content. Electrochemical corrosion tests reveal that the addition of Mo in quaternary Ni-Co-Mo-B increases corrosion performance in saline environments but reduces corrosion performance in acidic environments over Ni-Co-B amorphous alloy. Differential scanning calorimetry (DSC) scan shows that prepared amorphous-nanocrystalline material has thermal stability up to 346 degrees C without undergoing phase change.