Preparation And Property Research Of Ni-P Composite Coatings Doped And Modified By Micro-nanometer Particles

In industrial production,wear and corrosion are main factors for the failure of mechanical equipment,which can bring in problems,such as resources waste,personal damage,environmental pollution and economic losses.At present,a single coating is difficult to maintain the long-term stability under bad working conditions,such as high temperature,high pressure and high wear,so the development of high-performance composite coatings has attracted wide attention.There are many researches about nickel phosphorus composite coatings,especially multi-functional nickel phosphorus matrix composite coatings.This study focuses on the regulation of Ni-P electrodeposited process and the improvement of electroplating solution.The introduction of the third phase particles can obtain multifunctional nickel alloy composite coatings with excellent properties and give full play to its advantages in harsh working conditions.Main results are as follows:(1)Ni-P coatings have been prepared by the electrodeposited technology.The relationship between properties and technological parameters of Ni-P coatings has been systematically studied.These results show that changes in technological parameters have great effects on content of Ni and Ni3P and surface morphology.In order to obtain the best resistance to salt spray corrosion and the highest microhardness(about 660 kg.mm-2),the electrodeposited parameters of Ni-P coatings are controlled at the temperature of 50?,the current density of 2 A.dm-2 and the bath pH value of 3?4.The exploration of technological parameters lays a foundation for the optimization of the Ni-P coating.(2)Ni-P-Ti3C2Tx composite coatings have been prepared by doping Ti3C2Tx particles into Ni-P coatings by the composite electrodeposited technology.The dendritic structure appears on the surface of Ni-P-Ti3C2Tx composite coatings and the surface wettability changes from hydrophily to hydrophobicity.In the corrosive medium of 3.5 wt%NaCl solution,when the concentration of Ti3C2Tx particles in the bath is 6 g·L-1,the electrochemical corrosion resistance of Ni-P-Ti3C2Tx composite coatings is the best and the Rct(charge transfer resistance)increases from 96.8 ?·cm2(Ni-P coatings)to 217.7 ?·cm2,so the corrosion rate decreases.When concentration of Ti3C2Tx particles in bath is 4 g·L-1,the maximum microhardness of Ni-P-Ti3C2Tx composite coating is the highest,which is about 900 kg·mm-2,and the wear resistance of Ni-P-Ti3C2Tx composite coatings is the best under the condition of 5 N and 0.62 m·s-1.Compared with Ni-P coatings,the minimum wear loss is reduced by about 90%,but the average coefficient of friction is increased.(3)In order to improve the wear resistance of Ni-P-Ti3C2Tx composite coatings,Ti3C2Tx is modified by MoS2 to obtain Ti3C2Tx/MoS2 composite particles.In addition,Ni-P-Ti3C2Tx/MoS2 composite coatings have been prepared by doping Ti3C2Tx/MoS2 composite particles into Ni-P coatings.The doping of Ti3C2Tx/MoS2 composite particles makes the surface morphology with the appearance of a cauliflower like structure and surface roughness increases continuously.When the concentration of Ti3C2Tx/MoS2 in the bath is 6 g·L-1,the surface hydrophobicity of Ni-P-Ti3C2Tx/MoS2 composite coatings increases further with the maximum contact angle of 138.64°,the electrochemical corrosion resistance is the best in the corrosive medium of 3.5 wt%solution and the Rct increases from 96.8 ?·cm2(Ni-P coatings)to 312.4 ?·cm2,so the corrosion rate decreases.In addition,the microhardness is the largest,which is about 1200 kg·mm-2,and the wear resistance is the best.under the condition of 5 N and 0.62 m·s-1,compared with Ni-P-Ti3C2Tx composite coatings,the minimum wear loss and the average coefficient of friction are reduced by about 79%and 59%,respectively.(4)The mechanism of electrochemical corrosion and frictional wear of Ni-P-Ti3C2Tx/MoS2 composite coatings have been analyzed.By studying the hydrophobic surface of Ni-P-Ti3C2Tx/MoS2 composite coatings,it is found that hydrophobic particles are enriched and the hydrophobic Cassie-Baxter state is maintained on the surface.By observing the electrochemical corrosion behavior of the Ni-P-Ti3C2Tx/MoS2 composite coating in the corrosive medium of 3.5 wt%NaCl solution,it is realized that Ti3C2Tx/MoS2 particles promote the surface passivation,and the physical barrier effect can prevent penetration of corrosive medium.By analyzing reasons of changes in wear rate and wear mechanism for Ni-P-Ti3C2Tx/MoS2 composite coatings,it is realized that Ti3C2Tx/MoS2 particles can not only form a surface adsorption film to play the lubricative effect,but also can form a frictional protective film to play the self-repair effect.