Influence of Zirconia Incorporation on the Mechanical and Chemical Properties of Ni-Co Alloys

Abstract Ni-Co-ZrO 2 nano-composites are electrodeposited from sulphamate electrolyte and a comparison is made with Ni-ZrO 2 in terms of structure and properties. The Co content in the coatings is in the range of 10-80wt%. The deposition conditions like current density, pH are optimized in terms of microhardness and amounts of ZrO 2 incorporated. The microhardness studies revealed that the maximum hardness is exhibited by Ni-28Co-2ZrO 2 composite. The FESEM study showed a change in morphology from polyhedral to ridge with increase in Co content from 10 to 80wt%. A change in crystal structure from fcc to hcp is also seen. The effect of annealing treatment in terms of microhardness is studied by subjecting the composite electroforms to 800℃. The Co rich composite exhibited better stability compared to Ni rich composites. Ni-28Co-2ZrO 2 composite exhibited better immersion corrosion resistance while, Ni-ZrO 2 composite displayed better electrochemical corrosion resistance. The wear studies showed that Ni-10Co-2ZrO 2 , Ni-28Co-2ZrO 2 composites showed better resistance. Thus, it is seen that the coatings can be tailored to suit various applications

Studies on electrodeposited nickel–yttria doped ceria composite coatings

Incorporation of ceria particles into the Ni matrix was found to improve the corrosion resistance of pure Ni coatings. With the aim of further improving the corrosion resistance of Ni-ceria, yttria was doped with ceria and used as distributed phase. About 8-mol% yttria doped ceria (8YDC) particles synthesized by a solution combustion process were dispersed in a nickel sulfamate bath and electrodeposition was carried out to prepare Ni–8YDC composite coatings at various current densities. The microhardness of the composite coatings was determined. Optical microscopy confirmed the incorporation of 8YDC particles into the Ni matrix. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to characterize the corrosion behavior of the Ni–8YDC coatings. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) were used to characterize the corroded samples. The results were compared with those for Ni and Ni–CeO2 coatings. The wear behavior of Ni–8YDC was studied. Wear tracks were characterized by MicroRaman Spectroscop

Multifunctional electrodeposited Ni-mullite composite coating

Nickel based composite coatings have attracted a lot of interest particularly for wear resistant and corrosion resistant applications. Among the various composite coatings Ni-SiC is of special interest as it is commercially used as wear resistant coating in rotary and reciprocating engines. However, at temperatures above 450oC SiC reacts with the nickel matrix to form brittle nickel silicide which deteriorates the performance of the Ni-SiC coating. Oxide particle reinforced nickel composite coatings can be an alternate to Ni-SiC coating as the distributed phase- oxides are thermally more stable compared to carbides. In the present study, mullite (3Al2O3.2SiO2) particles have been reinforced in nickel matrix. The advantages of mullite include low thermal conductivity, excellent creep resistance, high-temperature strength, and good chemical stability. The electrodeposition conditions were optimized to obtain maximum particle incorporation. The thermal stability of electrodeposited Ni-mullite coating in terms of microhardness was studied at temperatures upto 800oC and compared with Ni-SiC coating. The hardness value of as plated electroforms was similar for both Ni-mullite and Ni-SiC coating (400Hk). A marginal decrease in the microhardness of Ni-mullite coating occurred at temperatures of 600oC while, significant reduction was observed beyond 400oC for Ni-SiC coating. Thus, the incorporation of mullite particles in nickel matrix improves its thermal stability to a temperature of 600oC. The tribological studies showed that the wear volume loss for Ni-mullite coating is 2.38X10-5mm3/m while, that of Ni-SiC coating is 9.58X10-5mm3/m under identical testing conditions. The corrosion studies using potentiodynamic polarization and electrochemical impedance studies showed that the corrosion resistance of Ni-mullite coating is better than that of Ni-SiC coating. Thus, from the above studies it can be concluded that Ni-mullite has better wear and corrosion resistance compared to Ni-SiC coating in other words it is a multifunctional coatin

Influence of Cobalt on Manganese incorporation in Ni-Co coatings

The effect of alloying <1wt%Mn with plain Ni, Ni-Co alloys and plain Co coatings in terms of the structure and properties has been studied. The alloys were electrodeposited from an additive free sulphamate electrolyte. The Mn concentration in the electrolyte was maintained at 5g L-1 so as to obtain less than 1wt%Mn content in the alloy coatings. The Energy Dispersive X-ray analysis (EDX) showed that the Mn content reduced from 0.97wt% to 0.05wt% with increase in Co content from 0 wt% to 98wt% in the alloy coating. An increase in microhardness was obtained on the addition of Mn to Ni/Ni-Co alloys. The X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) studies revealed a change in crystal structure and morphology. Pin-on-disc tribology test revealed better wear performance of Ni-18wt%Co-Mn alloy coating compared to the other Ni-Mn/Ni-Co-Mn alloy coatings

Influence of Zirconia Incorporation on the Mechanical and Chemical Properties of Ni-Co Alloys

Ni-Co-ZrO2 nano-composites are electrodeposited from sulphamate electrolyte and a comparison is made with Ni-ZrO2 in terms of structure and properties. The Co content in the coatings is in the range of 10-80wt%. The deposition conditions like current density, pH are optimized in terms of microhardness and amounts of ZrO2 incorporated. The micro-hardness studies revealed that the maximum hardness is exhibited by Ni-28Co-2ZrO2 composite. The FESEM study showed a change in morphology from polyhedral to ridge with increase in Co content from 10 to 80wt%. A change in crystal structure from fcc to hcp is also seen. The effect of annealing treatment in terms of microhardness is studied by subjecting the com-posite electroforms to 800℃. The Co rich composite exhibited better stability compared to Ni rich composites. Ni-28Co-2ZrO2 composite exhibited better immersion corrosion resistance while, Ni-ZrO2 composite displayed better elec-trochemical corrosion resistance. The wear studies showed that Ni-10Co-2ZrO2, Ni-28Co-2ZrO2 composites showed better resistance. Thus, it is seen that the coatings can be tailored to suit various applications

Electrodeposited nickel composite coating containing in-situ nickel impregnated alumina particles

In this paper, preparation of nickel composite coating containing in-situ impregnated alumina particles is reported for the first time. Nickel impregnation in alumina particles was realized during electrodeposition through the pores present in the alumina particles that acted as conduits. The impregnation of Ni was confirmed by scanning electron microscopy and electron probe microanalysis. This study suggests that the use of porous particles may be a preferred route to improve the adhesion of particles and microhardness in electrodeposited metal matrix composites