Study On The Interaction Between Corrosion And Wear Of Marine Mooring Chain Steel In Seawater

With the increasing demand of marine engineering,the problem of corrosion and wear of metallic materials in the marine environment has attracted more and more attention.The exploration of marine resources is now gradually moving towards deep seas.Except for ultra-deep sea dynamic positioning systems with high technological content,the positioning and berthing of most other marine engineering equipment need to rely on catenary anchor leg mooring(CALM).The system is in a harsh marine environment,during the service of the mooring chain,safety problems such as damage,breakage and failure often occur due to the interaction of corrosion and wear.People have researched the corrosion and wear behavior of typical metal materials in the marine environment,but it is still not well known about special steels with high requirements and high performance,such as mooring chain steel.Based on this,this thesis took the commonly used marine mooring chain steel 22 Mn Cr Ni Mo as an object to discuss the corrosion and wear behavior and their interaction of mooring chain steel in the mooring system under the marine environment.Firstly,the electrochemical properties of mooring chain steel 22 Mn Cr Ni Mo materials were measured at different constant potentials and different dynamic potential scanning rates through an electrochemical workstation,then under the conditions of pure water and seawater,the tribological properties of the22 Mn Cr Ni Mo mooring chain steel samples were tested under different contact stresses and sliding velocities,the changes of friction coefficient,wear volume loss and wear rate were compared and analyzed.The corrosion and wear surface morphology was observed and analyzed with a scanning electron microscope(SEM).The three-dimensional morphology of the wear scar was observed with a laser confocal microscope,and the profile of wear mark and wear volume loss were measured.The results show that the contact stress had less influence on the friction coefficient,volumetric wear and wear rate of the friction pair than the sliding velocity.By examining the wear morphology of mooring chain steel 22 Mn Cr Ni Mo,under the condition of fretting wear,the wear mechanism of mooring chain steel 22 Mn Cr Ni Mo was coexistence of abrasive wear and adhesive wear.As the sliding velocity increased,the abrasive wear mechanism gradually changed to the adhesive wear mechanism,the friction coefficient value and its increase also gradually increased.Compared with pure water,seawater reduced the friction coefficient of mooring chain steel friction pairs by a maximum of 56.3%.The wear loss and wear rate of mooring chain steel in seawater were lower than those in pure water under the same test conditions,indicating that corrosion inhibited wear;as the degree of wear increased,the degree of corrosion became more and more serious,indicating that wear promoted corrosion,which indicated that during the fretting corrosion and wear of mooring chain steel,there was a conversion between positive and negative interactions between corrosion and wear.The corrosion and wear mechanism of mooring chain steel was analyzed by the micro-morphology of the corroded and worn surface.The wear mechanism of mooring chain steel was typically abrasion wear in pure water,and the wear mechanism was mainly corrosion fatigue in seawater.