| With the country’s increasing emphasis on the development and utilization of marine resources,the marine shipbuilding industry has developed rapidly.Ships serve in the marine environment and are exposed to and destroyed by various corrosive conditions.Among them,cavitation corrosion is the most destructive type of corrosion in the marine environment due to the combined effect of electrochemical corrosion and mechanical impact.Nickel aluminum bronze alloy has good mechanical properties,corrosion resistance and anti-sea biofouling performance,and is used in ship propellers,sea water pumps and other parts that suffer from cavitation corrosion.However,with the continuous improvement of marine ships’sailing speed,working conditions,and use requirements,there is an urgent need to develop new cavitation-resistant corrosion-resistant materials.In recent years,some new nickel aluminum bronze alloys have been developed,showing potential application prospects.However,the cavitation corrosion behavior of these alloys in the seawater environment is still lacking in systematic experiments and research.Before batches are put into marine equipment and marine engineering applications,it is very necessary to investigate the cavitation corrosion behavior of nickel aluminum bronze alloys in the seawater environment.Regularly carry out relevant research work to provide technical support for the application of materials and corrosion control.In this paper,two typical nickel aluminum bronze alloy materials,QAl10-4-4 and QAl9-4-4-2,which have good application prospects,are selected,and the two alloys are systematically studied by comprehensive use of electrochemical testing and microscopic characterization techniques.The static corrosion and cavitation corrosion behaviors in simulated seawater,and based on the comparative analysis of the cavitation corrosion behavior and corrosion resistance of the two alloys,the mechanism of cavitation corrosion resistance of nickel aluminum alloys was explored.The main research contents and findings are as follows:1.According to the needs of simulated cavitation corrosion test of nickel aluminum bronze alloy in the laboratory,a special ultrasonic cavitation generating device is customized according to ASTM G32-10 standard,and the temperature control is realized by integrating the circulating water-cooling device.An on-line cavitation corrosion test platform is established,which solves the technical problems of simulated cavitation corrosion environment and on-line test.2.The corrosion behavior of QAl10-4-4 nickel aluminum bronze in static seawater was studied by EIS,polarization curve and electrochemical noise.The results show that QAl10-4-4 nickel aluminum bronze will form a protective corrosion product film with the increase of immersion time in static seawater,so that the metal has good corrosion resistance.The maximum charge transfer resistance of the alloy reaches 38930Ω·cm2 after immersion in seawater for 240hours,the corrosion current density reaches the minimum value of 9.3246×10-7A·cm-2.On this basis,the cavitation corrosion behavior of QAl10-4-4 nickel aluminum bronze in simulated seawater was studied by EIS,polarization curve,SEM,ultra depth of field microscope and XRD.The results show that compared with static seawater corrosion,the cavitation corrosion has a more serious damage to the alloy surface,and its charge transfer resistance reaches the minimum value of 95.21Ω·cm2 when the cavitation corrosion is the most serious,the corrosion current density reaches the maximum value of 1.8912×10-4A·cm-2,the maximum corrosion depth is 75μm.3.The corrosion behavior of QAl9-4-4-2 nickel aluminum bronze in static seawater was studied by EIS,polarization curve and electrochemical noise.The results show that QAl9-4-4-2 nickel aluminum bronze will form a protective corrosion product film with the increase of immersion time in static seawater,so that the metal has good corrosion resistance.The maximum charge transfer resistance of the alloy reaches 91710Ω·cm2 after immersion in seawater for 240hours,the corrosion current density reaches the minimum value of 4.3107×10-7A·cm-2.On this basis,the cavitation corrosion behavior of QAl10-4-4 nickel aluminum bronze in simulated seawater was studied by EIS,polarization curve,SEM,ultra depth of field microscope and XRD.The results show that compared with static seawater corrosion,the cavitation corrosion has a more serious damage to the alloy surface,and its charge transfer resistance reaches the minimum value of 119.7Ω·cm2 when the cavitation corrosion is the most serious,the corrosion current density reaches the maximum value of 1.3199×10-4A·cm-2,the maximum corrosion depth is 50μm.4.Based on the above test and research results,the cavitation corrosion resistance of two nickel aluminum bronze materials was compared and analyzed,and the cavitation corrosion resistance mechanism of the alloy was explored.The results of corrosion weight loss,polarization curve,EIS and corrosion morphology showed that the cavitation corrosion resistance of QAl9-4-4-2 was better than that of QAl10-4-4.EDS test results show that the unique Mn element of QAl9-4-4-2 has a significant effect on the cavitation corrosion resistance of the alloy.In addition,XRD test results show that phaseα,phaseβ’and phaseκin QAl10-4-4 are more seriously damaged by cavitation corrosion.Based on the above test and analysis results,the mechanism of cavitation corrosion resistance of QAl9-4-4-2 alloy is as follows:in QAl9-4-4-2 nickel aluminum bronze,phaseκhas finer size,and phaseκwith higher hardness can not only exist more stably under the condition of cavitation corrosion environment,but also effectively slow down the corrosion damage of other phases during cavitation corrosion.Compared with QAl10-4-4 nickel aluminum bronze,the existence of Mn element makes theκphase of QAl9-4-4-2 nickel aluminum bronze refined,so QAl9-4-4-2 nickel aluminum bronze has better corrosion resistance. |
PDF Full Text Request