Preparation Of Nickel-based Alloy Coatings And Their Wear And Corrosion Resistance

Ni-W alloy coatings are widely used in energy,petrochemical,aerospace and other fields because of their excellent wear resistance,corrosion resistance,mechanical and mechanical properties.ZrB₂is a hard ceramic material with high hardness,high load-bearing capacity and excellent corrosion resistance,while BN（h）is a two-dimensional laminate material with large transverse dimension ratio and laminate structure,thus It has unique self-lubricating properties.In this thesis,a composite coating containing ZrB₂ and BN（h）was prepared using Ni-W as the base metal.The tribological properties of Ni-W,Ni-W/ZrB₂,and Ni-W/ZrB₂-BN（h）coatings were investigated,and the influence of the microstructure of the coatings on their corrosion resistance was thoroughly explored.The specific studies are as follows:（1）The Ni-W alloy plating was prepared on the surface of 45^#steel by pulsed electrodeposition,and the effects of process parameters such as current density and duty cycle on the structure and properties of Ni-W alloy plating were investigated,and the optimal process parameters for Ni-W electrodeposition were determined by experiments.The experimental results show that when the current density is 2 A/dm²and the duty cycle is 40%,the Ni-W alloy plating is more flat and dense,with good hardness（572 HV）,wear and corrosion resistance.（2）Ni-W/ZrB₂ composite plating was prepared by composite electrodeposition with ZrB₂,a hard ceramic material,as the reinforcing phase under the optimal pulse process parameters,and it was found that the addition of ZrB₂significantly changed the surface morphology of Ni-W alloy plating and reduced the generation of defects such as pinholes.The grain size of the alloy plating was also reduced,and the minimum grain size was 7.32 nm.when the concentration of ZrB₂ was 2 g/L,the Ni-W/ZrB₂composite plating had a high hardness（747 HV）and the best corrosion resistance in3.5 wt%Na Cl solution with a corrosion current density of 4.329μA·cm^-2.（3）Based on the study of Ni-W/ZrB₂ composite plating,Ni-W/ZrB₂-BN（h）composite plating was prepared by changing the addition amount of BN（h）in the plating solution.The experimental results showed that the addition of BN（h）particles changed the surface morphology and structure of the composite layer,improved the hardness of the layer,decreased the friction coefficient and wear rate with the addition of BN（h）and then increased the wear rate.Its minimum wear rate is 5.38×10-6mm³/N·m.This is attributed to the fact that BN（h）acts as a lubricant during the friction process.In addition,the composite coating has the highest corrosion potential of-0.360V in static corrosion tests,and the corrosion current density can be as low as 1.793μA·cm^-2.