چكيده به لاتين
Electroplating is One of the best methods for producing nanocomposite coatings. Nanocomposite coatings are widely used in automotive, aerospace and electronics industries due to its hardness, high corrosion resistance and abrasion resistance, unique mechanical properties, sulf-lubrican and thermal stability. Nickel Cobalt composite coatings properties include more high hardness, better corrosion resistance and wear resistance than pure nickel. The use of MWCNT Nanoparticle provides good functional properties including high elastic hardness and modulus, good elasticity, unique conductivity with minimal friction coefficient and excellent wear resistance to Ni-Co / MWCNT coatings. In this research, Ni-Co / MWCNT composite coatings using direct and reverse pulsed electroplating using Watts bath including nickel sulfate, cobalt sulfate and nickel chloride and 0.5 and 1 g / L MWCNT particles with an average diameter of 9.5 nm and An average length of 1.5 nm was applied to the steel substrate for 90 minutes at room temperature and the effect of duyt cycle parameters, average current density and MWCNT nanoparticle concentrations on the microstructure, the amount of particles present in the coating using Scanning Electron Microscopy (SEM) and analysis EDS was investigated. The microhardness of the samples was also evaluated using a Vickers microplate meter, and then an optimum coating was applied by reverse pulsed electroplating. The size of the crystallite and the crystalline orientation were determined by using X-ray diffraction analysis in some coatings and the resistance to wear was measured with a pin-disk device. The results showed that Ni-Co / MWCNT composite coatings produced by Direct Pulse Electroplating (PC) at 60% duty cycle, average current density 2 A / dm2 and 1 g / L MWCNT has, 0.5% MWCNT in coating and highest microhardness. Reverse pulsed Electroplating (PRC) was used to provide this coating to increase the weight percentage of MWCNT nanoparticles contained to 1.54%, and reducing the crystallite size, increasing microhardness and improving wear resistance. The Ni-Co / MWCNT composite coatings produced in optimum direct pulse (PC) conditions had 0.5% MWCNTs, a crystallite size of 37.5 nm, 317 HV (8. 9% increased in comparison with Ni-Co) the coefficient of friction was 0/53 μ in applied force of 1 N (22.9% reduction), wear rate 0.8 in μg / m in applied force of 1 N (71.57% decrease) and In reverse pulse conditions (PRC), in terms of the amount of MWCNTs present in the coating, it contains 1.54% MWCNTs, a crystallite size of 30.7 nm, 450 HV microhardness (40.7% higher than Ni-Co, The coefficient of friction was 0.54 μ in applied force of 1 N (20.4% reduction), wearing rate 0.65 μg / m The applied force was 1 N (76.17% decrease).
