Research On Preparation And Properties Evaluation Of Nickel-based Wear-resistant Self-lubricating Coatings In Wear-prone Areas Of Oil And Gas Storage And Transportation Facilities

To improve the service durability and reliability of the contact area of oil and gas storage and transportation facilities and break through the bottleneck of lubrication technology of the contact area under extreme service environment,the preparation and performance evaluation of wear-resistant self-lubricating coatings were studied,Its content of the study was as follows:Firstly,the preparation and performance evaluation of Ni60/nickel-coated graphite self-lubricating coating were carried out.The results showed that in the coatings of variable laser scanning speed,the coating,whose laser scanning speed was 500 mm/min,had a large amount of undissolved graphite in large size causing lots of crack and pore defects.The large size graphite in the early stage of wear was easy to form a lubricating film,but the graphite with low adhesion strength was prone to fall off in the later stage of abrasion and caused the increase of the friction coefficient;When the laser scanning speed was 200 mm/min,the coating had fewer surface cracks,lowest friction coefficient（0.54）and wear rate(1.6484×10^-6mm³/N·m);In the coatings of variable powder feeding rate,the coating,whose powder feeding rate was 5 g/min,had fewer cracks and the lowest friction coefficient（0.46）since small size graphite phases distributed in the coating;The coating whose powder feeding rate was 20 g/min had the lowest wear rate(1.1889×10^-6mm³/N·m),but the coating had a lot of crack and pore defects and made the friction coefficient of the coating to fluctuate greatly.Secondly,to suppress the crack defects of the coating,the nickel-coated graphite coating was prepared with a slow scanning speed and a small powder feeding amount.The results showed that there were still cracks on the coating surface and the coating’s friction coefficient reached up to 1.21,and the coating’s wear rate was 12.6806×10^-6mm³/N·m.To reduce the dilution effect of the substrate on the coating and suppress the crack defects,the coatings of variable transition material were prepared.The results showed that among the coatings of variable transition layer materials,the nickel-clad aluminum transition coating had the less friction coefficient（0.62）and wear rate(6.1111×10^-6mm³/N·m),but there were some cracks on the surface of the coating.Then,to further suppress coating crack defects and reduce the wear rate of the coating,the nickel-coated graphite coatings in different substrate preheating temperatures were prepared.The results showed that the coating in the preheating temperature of 200℃had a uniform hardness,fine grains,and lower wear rate(1.3762×10^-6mm³/N·m),but there were still a few crack defects in the coating;As the substrate preheating temperature increased,the coating cracks decreased.When the preheating temperature is 300℃and 400℃,the coating had no crack defects;As the preheating temperature increased,the amount of melting graphite and carbides and the wear rate of the coating increased and the crystal grains coarsened.Finally,to obtain a coating without cracks and improve the wear resistance of the coating,Nd₂O₃was added to the nickel-coated graphite coating,and the effect of the changeable Nd₂O₃content on the performance of the coating was carried out.The results showed that when the Nd₂O₃content was 0.4 wt.%and 0.8 wt%,there was no crack defect on the coating surface.When the Nd₂O₃content was 2.0 wt%,there were a few cracks on the surface of the coating,and the friction coefficient of the coating was the smallest（0.44）,and the coating had the best anti-friction performance.When the Nd₂O₃content was 0.4 wt.%,the friction coefficient of the coating was 0.47,and the minimum wear rate of the coating was0.5141×10^-6mm³/N·m,and the coating had the best wear resistance.