Effect of Co content on electrodeposition mechanism and mechanical properties of electrodeposited Ni-Co alloy

• Ni-Co coatings with various cobalt contents were electrodeposited from modified Watts bath. The effect of cobalt content on electrodeposition mechanism of the coatings was studied by electro-chemical impedance spectroscopy method (EIS). Surface morphology and crystallographic structure of the coatings were investigated by means of SEM and XRD. Mechanical properties of the coatings were determined using Vickers microhardness and tensile tests. It was found that with increasing the Co2+ ions in electroplating bath, the charge transfer resistance (Rct) of Ni-Co film increased whereas the Warburg impedence decreased. This may be due to enhancement in coverage of cathode surface by Co(OH)2 and higher diffusion rate of metal ions towards cathode surface, respectively. Also, with increasing the cobalt content in the bath, cobalt content in the alloy coating increased anomalously and (111) texture consolidated gradually. With increasing the cobalt content up to 45% in alloy coating, the grain size decreased and consequently, hardness and strength of the alloy increased. Further enhancement of cobalt content up to 55% led to a little decrease in hardness and strength. The maximum ductility was observed for Ni-25%Co coating due to relatively small grain size and compact structure. © 2016 The Nonferrous Metals Society of China.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

Keyword

electrodeposition

mechanical properties

microstructure

Ni-Co coating

Cathodes

Charge transfer

Coatings

Cobalt alloys

Corrosion

Electrodes

Grain size and shape

Hardness

Metal cladding

Metal ions

Metals

Nickel

Spectroscopic analysis

Tensile testing

Cathode surface

Charge transfer resistance

Compact structures

Crystallographic structure

Electrodeposition mechanism

Electroplating bath

Small grain size

Vickers microhardness

Cobalt

Publication and Content Type

ref (subject category)

art (subject category)