Study On The Key Factors To Improve The Comprehensive Properties Of Ni-P-Al₂O₃ Nanocomposite Coating

In order to protect the vulnerable parts of industrial equipment in the friction and wear environment,many scholars have carried out the process research of one-dimensional nano functional composite coating,and found that adding nano solid particles with special properties can significantly improve the performance of the composite coating.For example,nano particles such as Al₂O₃,Si C and diamond can significantly enhance the wear resistance of the composite coating;Nano particles such as Mo S₂,PTFE and graphene can reduce the friction coefficient of the composite coating and increase its self-lubricating property.The preparation process of Ni-P-Al₂O₃ nanocomposite coating has been continuously optimized by many scholars.Ni-P-Al₂O₃ composite coating with good wear resistance and corrosion resistance can be prepared,and it is widely used in the field of mechanical industry.However,the friction coefficient of Ni-P-Al₂O₃nanocomposite coating is large,and the coating is still prone to wear in the actual working state,especially in the dry friction environment.The friction coefficient of polytetrafluoroethylene(PTFE)is very low,and its nanoparticles have excellent self-lubricating properties.Therefore,in order to further improve the comprehensive performance of Ni-P-Al₂O₃ nanocomposite coating,this topic is to dope PTFE nanoparticles into Ni-P-Al₂O₃ plating solution,prepare and study Ni-P-Al₂O₃-PTFE binary nanocomposite coating,and focus on the key factors to improve the comprehensive performance of Ni-P-Al₂O₃ nanocomposite coating.Firstly,the dispersion and synergistic deposition mechanism of Al₂O₃-PTFE binary nanoparticles were studied to explore its effect on friction reduction and wear resistance of Ni-P-Al₂O₃-PTFE composite coating.Then,the effect of current density on the deposition amount of binary nanoparticles and the comprehensive properties of the composite coatings were studied.Finally,the effect of substrate surface roughness on the uniformity distribution of binary nanoparticles and the bonding strength of the composite coating was discussed.The main research contents are as follows:(1)The effects of different dispersants A,B and C on the dispersion of Al₂O₃-PTFE binary nanoparticles were studied by single factor analysis.In this study,the particle size of nanoparticles in the plating solution was measured and compared by a laser particle size analyzer,and then the dispersant-dispersant A with better dispersion effect was selected,which laid the foundation for the subsequent study of the plating solution configuration.(2)Based on the previous study of Ni-P-Al₂O₃ wear-resistant coating by our research group,PTFE particles were added to the plating solution to study the effect of PTFE addition amount on the Al₂O₃ content and friction-reducing wear resistance of the deposition layer.Through the interaction test,Al₂O₃-PTFE binary nanoparticles with different mixing ratios were used as reinforcements to prepare the composite coating.The surface morphology of the composite coating and the deposition amount of binary nanoparticles in the composite coating were evaluated to determine the optimal mixing ratio of Al₂O₃-PTFE binary nanoparticles,so as to explore the synergistic deposition mechanism of Al₂O₃-PTFE binary nanoparticles.The results show that the deposition of Al₂O₃ in the composite coating increases with the increase of PTFE deposition,but when the PTFE addition in the plating solution is too large,the deposition of both will decrease.When the Al₂O₃ content is 70 ml/L and PTFE content is 30 ml/L,the surface morphology of the composite coating is smooth and dense,and the antifriction and wear resistance is better.(3)The plating solution was prepared by mixing dispersant A with the same binary nanoparticles,and the Ni-P-Al₂O₃-PTFE composite coating was prepared by changing the current density.The deposition amount of Al₂O₃-PTFE binary nanoparticles in the deposition layer,the surface morphology of the composite coating,the corrosion resistance of the composite coating,,the friction and wear resistance and elastic-plastic mechanical properties of the composite coating were tested to optimize the optimal current density and to study the relationship between the current density and the deposition amount of nanoparticles in the composite coating.The results show that the deposition amount of Al₂O₃-PTFE binary nanoparticles increases first and then decreases with the increase of current density.When the current density is 3 A/dm~2,the grain size of the composite coating is fine,and the deposition amount of nanoparticles is large.Compared with Ni-P-Al₂O₃ composite coating,the friction coefficient of Ni-P-Al₂O₃-PTFE composite coating is reduced by 60%under the premise of ensuring corrosion resistance and hardness.(4)The distribution uniformity of Al₂O₃-PTFE binary nanoparticles was observed by changing the surface roughness of the substrate.The smoothness of the sample surface before and after deposition was compared;The bonding strength,antifriction wear resistance and elastic-plastic properties of the composite coating were tested.Finally,the surface roughness of the substrate corresponding to the Ni-P-Al₂O₃-PTFE composite coating with excellent performance and good surface smoothness was determined to be about 89nm.The results show that when the substrate surface roughness is 89 nm,the composite coating has the highest bonding strength,which is 38 N;the hardness of the composite coating is the highest,with a value of 583 HV.The average friction coefficient of the composite coating is 0.09,and the comprehensive performance is good.By adding PTFE particles into Ni-P-Al₂O₃ plating solution,the synergistic deposition mechanism of Al₂O₃-PTFE was clarified,and the better current density and substrate surface roughness were studied.The Ni-P-Al₂O₃-PTFE composite coating with good anti-friction and wear resistance and high bonding strength was obtained,which significantly improved the anti-friction and wear resistance of Ni-P-Al₂O₃composite coating.