Tribological characteristics of nickel based composite coatings

Nanometer Diamond (ND) was synthesized by using the detonation method. It was a kind of materials with properties of diamond and nanometer particle. The Ni–P–ND composite coating was prepared from a suspension of diamond nanoparticles in electroless bath. The tribological properties, hardness and corrosion behaviours of the composite coating on medium carbon steels were investigated. The Ni–P–ND composite coating exhibits not only high wear resistance but also low friction coefficient compared with the Ni–P composite coating. The highest microhardness of the Ni–P–ND composite coating was obtained by heat treated at 673 K. The corrosion resistance of Ni–P–ND composite coating is superior to that of Ni–P coating. The mechanisms of improvement of the tribological and electrochemical properties of the electroless composite coating are also discussed.

Synthesis and properties of electroless Ni–P–Nanometer Diamond composite coatings

Corrosion characteristics of cobalt-silicon nitride electro composites in various corrosive environments

In the present study, an attempt has been made to use dispersed ceramic and polymer particles to produce nickel hybrid composite coatings and to evaluate the effect of these particles on the electrochemical corrosion of these coatings. A nickel-plating bath with low concentration of nickel ions (45 g/dm 3 ), brightening agent, surfactants, and dispersed particles of SiC with PTFE or CFx were used for deposition of the hybrid composite electrochemical coatings. Scanning electron microscopy (SEM) was used to examine the deposit morphology with EDX (LEO 435VPi and LEO 1530) in order to determine the composition of nanocrystalline composite coatings on the same surfaces. The weight percentage of the dispersed phase in the coatings was determined gravimetrically. A Siemens D500 Diffractometer with Si[Li] radiation was used to examine texture and grain size. A voltammetric method was used for examination of the samples of hybrid composite coatings. After surface degreasing with acetone in an ultrasonic...

INVESTIGATION OF THE ELECTROCHEMICAL CORROSION RESISTANCE OF HYBRID Ni-SiC-FLUOROPOLYMER COMPOSITE COATINGS

Fatigue behaviour of nickel-flyash composite coatings

The electrochemical behaviour of sediment electrodeposited nickel-silicon nitride composite coatings on mild steel has been studied. These composite coatings provide better corrosion resistance in both 3.5% NaCl and 0.5M H2SO4 solution than nickel coatings. The higher the percentage of silicon nitride in the composite, the better is the corrosion resistance. Microstructural studies on these composite coatings have revealed the retention of silicon nitride particles in the coating after corrosion tests, which was indicative of very little or no galvanic corrosion. A reduced tendency to pitting of the composite coatings as compared to nickel coatings was also observed. X-ray analysis of composite coatings exposed to 0.5M H2SO4 revealed the presence of silicon dioxide in them, leading to enhanced passivation of the composite coatings with respect to pure nickel.

K. J. L. Iyer

Papers

Corrosion Studies on Nickel-Silicon Nitride Composite Coatings