Ni-nano SiC composite coating

Effect of electrodeposited Ni-nano SiC composite coatings on the corrosion wear of steel and stainless steel... 

Surface profile measured at the middle of the wear scar and the corresponding roughness parameters of (a) ED pure nickel coating and (b) ED Ni-nano SiC composite coating obtained at a normal sliding load of 20 N, under the same test conditions as Fig. 8.19 (Benea et al., 2002). 

Incorporation of nanosized SiC particles in the EL NiP matrix increased the hardness from 627 43 to 704 60HVqqj. However, incorporation of micronsized SiC particles increased the hardness to 1669HVqqj. The cumulative mass loss versus time (see Fig. 8.26) due to cavitation erosion corrosion in 3.5% NaCl is found to be very low for EL Ni-P-nano SiC composite coating compared with its coimterpart incorporating micron-sized SiC particles. The EL Ni-P-nano SiC coated specimen exhibits a smooth and uniform surface after the cavitation erosion corrosion test with no visible pits (see Fig. 8.27). The uniform distribution of the nanosized SiC particles in the EL NiP matrix (R 0.95 0.060 pm) inhibits the formation of pits. However, the higher surface roughness (R 1.72 0.051 pm) promotes bubble formation and causes detachment of the SiC particles, which results in the formation of small cavities on the surface of EL Ni-P-micro SiC coated steel (see Fig. 8.27). Hence, it is evident that incorporation of nanosized particles in EL NiP matrix could provide a better cavitation erosion corrosion resistance and inhibit the onset of erosion damage near surface defects. 

Lin and He (2005) have compared the role of eleetroless (EL) NiP composite coatings incorporated with micron- and nanosized SiC partieles on the cavitation erosion of AISI1045 steel. The EL Ni-P-nano SiC and Ni-P-micro SiC composite coatings were prepared by dispersing nano (25-50 mn) and micron- (5 pm) sized particles in an acidic hypophosphite-reduced EL nickel plating bath maintained at 90 1°C. The deposition time was 3 h and the coating thickness was 60 pm. All the coatings were subjected to post heat-treatment to achieve abetter hardness and wear... 

Benea L., Wenger F., Ronthiaux R. and Celis J. R. (2009), Tribocorrosion behaviour of Ni-SiC nano-structured composite coatings obtained by electrodeposition . Wear, 266, 398 05. (doi 10.1016/j.wear.2008.04.018)... 

Vaezi M, Sadmezhaad S, Nikzad L. Electrodeposition of Ni-SiC nano-composite coatings and evaluation of wear and corrosion resistance and electroplating characteristics. Colloids Surf A Physicochem Eng Asp 2008 315 176-82. 

Gyftou P, 8troumbouli M., Pavlatou E. A., Asimidis P. and 8pyrellis N. (2005), Tribological study of Ni matrix composite coatings containing nano and micro SiC particles ,E/ectroc/j/ra. Acta, 50,4544-50. (doi 10.1016/j.electacta.2004.10.090)... 

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