Optimization Of Preparation Process Of Composite Electrodeposited Nickel-based MoS₂ Self-lubricating Coating

Combined with the good lubrication performance of MoS₂ particles and the excellent high-temperature mechanical property of nickel-based alloy,the Ni-MoS₂ self-lubricating composite coatings can solve the serious friction and wear problems caused by insufficient lubrication under complex and severe conditions.With its advantages of flexible composite diversity and operation diversity,the composite electrodeposition has become a favorable choice for preparing Ni-MoS₂coatings.Aiming at the loose structure and reduced hardness of MoS₂ coatings prepared by composite electrodeposition,the present work had concentrated on the structure optimization and strengthening of the MoS₂ composite coatings by ultrasonic dispersion deposition and two-step electrochemical composite deposition.The ultrasonic cavitation effect was applied to suppress the stacking deposition of MoS₂ particles in the composite deposition process.Ni-MoS₂ coatings with good-quality and high-performance were obtained for the optimization of deposition mode.Utilizing the good fluidity and permeability of nickel solution,two-step electrochemical composite deposition was adopted to strengthen the structure of loose Ni-MoS₂ coating.A comparison of coating structure,depositing mechanism,and friction performance of Ni-MoS₂ coatings（stirred deposition of Mag-NM,ultrasonic deposition of US-NM;composite coating of Ni-MoS₂,two-step electrochemical composite deposition of Ni-MoS₂+Ni）was investigated by means of XRD,SEM,hardness and friction test.The research results show:（1）Mag-NM coating had a porous sponge-like structure by the by stacking lamellar MoS₂ particles.The hardness of Mag-NM coating reduced from 496.4 HV_0.1（pure Ni）to 97.6 HV_0.1,dropping by as much as 80.4%.US-NM coating obtained an optimized compact structure with fewer deposition defects,and its hardness was 453.9 HV_0.1.With the MoS₂ particles embedded,Ni-MoS₂ coatings exhibit lubricating performance.（2）Ni-MoS₂+Ni coatings performed a dense structure with nodular feature.The hardness of the Ni-MoS₂+Ni coatings rose to 282.0HV_0.1,being twice as much as that of the Ni-MoS₂ coating(130.7HV_0.1).Ni-MoS₂+Ni coating exhibited good anti-friction and abrasion resistance under long-term and heavy load conditions,indicating that second nickel deposition made the Ni-MoS₂+Ni coating with strengthened structure and optimized property.