| Ni-P alloy coating has been widely used as protective coating in chemical,machinery,electronics,aerospace and national defense industry and other fields.Metal matrix composite coating composed of metal matrix and the second phase particles has dual characteristics of matrix metal and composite particles.BN(h)is hexagonal structure which is similar to graphite.The layers are connected by Vander Waals force so that they are easy to slide and have excellent self-lubrication property.This paper mainly studies the preparation and properties of electrodeposition of Ni-P-BN(h)composite coating,the aim of the research is to prolong the working life of 45 carbon steel parts when their surfaces are plated low friction coefficient and good corrosion resistance coating.Electrodeposition method can be also used to repair metal parts which dimension is less than the tolerance size.First of all,the research object was Ni-P alloy on the basis of previous studies,the effects of deposition time and current density on the morphology,phase structure,surface roughness and microhardness were studied.Preferable processing parameters for preparation coating were current density of 7.0A/dm~2,electrodeposition time of 3h,the bath temperature of 60?.6 kind surfactants included sodium dodecyl sulfate(SDS),hexadecyl trimethyl ammonium bromide(CTAB),polyvinyl alcohol(PVA),triethanolamine(TEA),sodium dodecyl benzene sulfonate(SDBS)and polyethylene glycol(PEG)were comprehensively evaluated by calculating the hydrophilic lipophilic balance(HLB)value,measure BN(h)particle surface Zeta potential value,natural sedimentation and actual electrodeposition experiments.The distribution of current density and electric field during the deposition process were analyzed combining with CAE method,the results showed that the distribution of current density was uniformwhenelectric field was approximate to uniform electric field.The thickness of the coating was more uniform under the longer electrodeposition time.The simulation results were consistent with the actual experimental results.Secondly,the effects of different BN(h)particle concentration on the surface morphology,microhardness and friction properties of the composite coatings were studied,the results showed that the microhardness and friction coefficient of Ni-P-BN(h)composite coating decreased gradually with the increase of particle concentration,the microhardness value decreased from 555.18HV to 509.96HV and the friction coefficient value decreased from 0.406 to 0.219.The change of phase composition and microhardness of Ni-P alloy coating with Ni-P-BN(h)composite coating was compared during heat treatment.It was found that the microhardness of two kinds of coatings were improved after heat treatment,but Ni-P-BN(h)composite coating phase transition peak temperature value was higher than Ni-P alloy coating and the transformation from amorphous to crystalline process was slower than Ni-P alloy.Additionally,the corrosion properties of Ni-P-BN(h)composite coating in dilute hydrochloric acid,dilute NaOH solution,high concentration NaCl solution were studied.Ni-P-BN(h)composite coating in 1.0%hydrochloric acid immersion test showed that the corrosion current density presented an increasing trend,but the increase rate had downward trend.1.0%NaOH solution immersion test showed that the corrosion current density of the composite coating was very small,there was 2 to 3 magnitude smaller respect to the same concentration hydrochloric acid solution,the corrosion current density with increasing immersion time indicated a decreasing trend on the whole.10.0%NaCl solution immersion test showed that the corrosion current density also presented a decreasing trend on the whole.Ni-P-BN(h)composite coating had better corrosion resistance in hydrochloric acid,NaOH solution and NaCl solution compared with the 45 carbon steel.Finally,plane,cylindrical and bore dimension repair were preliminary attempted.Corroded allen wrench and bolt were protectively treated using electrodeposition method.The results showed that the repair of metal part dimension and the protection of corrosion parts surface using electrodeposition method were feasible. |
PDF Full Text Request