Friction And Wear Mechanism Analysis Of The Electro Brush Plating Ni-Mo Alloy

The Ni-Mo alloy coating not only has high mechanical strength but also has excellent wear resistance, corrosion resistance and heat resistance. Ni-Mo alloy coating can be used to replace hard chrome plating due to its low environmental pollution. In this thesis, a Ni-Mo alloy coating was produced by electro brush plating on 45#steel substrate, and the effects of the plating composition and process parameters on the Ni-Mo alloy coating surface morphology, microstructure hardness and wear resistance were analyzed. The structure and composition of electro brush plating Ni-Mo alloy were studied using XRD and SEM analysis, and the changes of Ni-Mo alloy coating physical and chemical properties were explored. Through investigation and analysis, the following could be concluded:1. The brush plating Ni-Mo alloy is crystalline in structure and it is a substitutional solid solution with nickel as solvent and molybdenum as solute. It has high binding strength with the substrate, and exhibits considerably high corrosion resistance and wear resistance performance.2. The voltage has the maximum effect on the brush plating among those process parameters involved in Ni-Mo alloy coating. The experimental results showed that the brush plating voltage and the relative velocity of electrodes have obvious effects on the brush plating deposition rate, micro hardness of coating, coating surface morphology and wear resistance, whilst the voltage exhibits the maximum effects.3. Modification of the process parameters may refine the coating structure, optimize the coating surface morphology, and improve the hardness and wear resistance. When the working voltage was 14 V and electrode relative velocity was 11.3m/min, the brush coating reached the maximum micro-hardness, the coating grains were refined, the coated layer was uniform and compact, leading to high wear resistance.4. When the nickel sulfate concentration in bath increased, the coating grain grew along the(111) crystal plane that has the dense arrangement of atom, and when the sodium molybdate concentration in bath increased, the coating grain grew along the(220) crystal plane.5. As the nickel sulfate and sodium molybdate concentration in bath were increased, the hardness and wear resistance were both increased, but the strengthening mechanisms were different: the increased concentration of the nickel sulfate refine the coating grain; the increased concentration of sodium molybdate led to more distortion and dislocation of the coating layer.6. In this thesis, a comprehensive analysis has been carried out regarding the effects of the bath composition on surface morphology and properties of the coating, and one kind of the Ni-Mo alloy solution was picked out as the best plating solution. When the nickel sulfate concentration is 400 ~ 500g/L, and sodium molybdate concentration is 25 ~ 30g/L, the brush plating coatings of Ni-Mo alloy not only has good surface morphology but also has the higher micro-hardness and the higher wear resistance.