Effect Of Self-generated TiC On Wear Resistance Of Martensitic Steels Applied For The Mid-groove Plate Of Scraper Conveyor

Low-alloy martensitic wear-resistant steel is the most widely used wear-resistant steel in China’s coal machinery industry because of its advantages of remarkable economic benefit,excellent and stable comprehensive performance.However,improving the wear resistance of the traditional low alloy martensitic steels by increasing the hardness will lead to poor machining performance and increase welding cracking tendency.Based on the research and development ideas of the second-phase reinforced wear-resistant cast iron,a new type of wear-resistant steel reinforced by micron-nano double scale Ti C particles with low alloy martensite was developed to solve the technical problem of improving the wear resistance of the wear-resistant steel without increasing the hardness or reducing the workability.However,there are few studies on the wear resistance of the new wear-resistant steel at present and the effect of Ti C on the wear resistance of martensitic steel is not clear.In view of the shortcomings of the new low alloy martensitic steel in wear,the wear behavior of commercial martensitic steel JFE400 and the new wear-resistant steels Ti20 and Ti60,which were independently developed and contained Ti C,under the conditions of certain stress load,impact load,gangue content(coal doped with 40 wt.% quartz sand)and acid corrosion(p H is about 3.5 mine water simulation fluid)were studied in combination with the service conditions of the mid-groove plate of scraper conveyor and the environmental medium conditions,so as to obtain the wear law of the new wear resistant steels.By analyzing the effect of Ti C particles on the wear resistance of new martensitic steel under different simulated working conditions,the mechanism of strengthening the wear resistance of martensitic steels by Ti C particles under different working conditions was obtained.The main conclusions of this paper are as follows:(1)The wear failure analysis of mid-groove plate under service condition was carried out.It is found that the wear failure mechanism of the plate surface is ploughing wear,but the wear failure mechanism at the joint of the plate with serious wear is mainly ploughing wear,and the peeling wear is the auxiliary wear mechanism.The impact effect intensifies the strip wear and accelerates the wear failure of the plate.Ploughing wear is due to micro-cutting caused by the relative sliding between the chain,coal and the mid-groove plate The main cause of the peeling wear is the transformation of the subsurface structure during the wear process,namely the micron size plate strip martensite structure into axial nanocrystals,the nanocrystallization of subsurface structure increases its hardness,leading to peeling cracking at the interface between deformation layer and matrix structure or deformation layer on one side of the initiation,peeling on the crack extended further,accelerate the loss of material.(2)In the three-body abrasive wear experiment without impact,the wear mechanism of the three experimental test steels under different simulated conditions is mainly ploughing wear.In the environment with low gangue content(dry coal not doped with quartz sand),the commercial steel JFE400 with higher matrix hardness shows better wear resistance than the wear-resistant steels Ti20 and Ti60.However,because Micron-scale Ti C has a certain effect on the ploughing behavior of hard abrasive,the new wear-resistant steels Ti20 and Ti60 show better abrasive wear performance than the commercial steel JFE400 in the environment with high gangue content(dry coal doped with 40 wt.% quartz sand).In acid corrosion environment(p H is about 3.5 mine water simulation fluid),Ti C will protrude from the matrix due to galvanic corrosion with the matrix.which hinders the ploughing behavior of coal and makes the Ti60 steel also exhibit excellent abrasive wear performance in acid corrosion and low gangue environment(coal doped with p H about 3.5 simulation fluid).However,acid corrosion will reduce the supporting effect of the matrix on the carbide,and the force of coal with high gangue content on the material is strong,leading to the carbide caving in the wear process.As a result,the wear performance of the new wear-resistant steel Ti60 is not as good as that of the commercial steel JFE400 under the coupling effect of high gangue and acid corrosion(coal doped with 40 wt.% quartz sand and then doped with 20 wt.%acid mine water simulation fluid).(3)In the abrasive wear experiment with impact effect,the wear mechanism of the three experimental steels under different simulated conditions is mainly ploughing wear,supplemented by peeling wear.The impact effect intensifies the material spalling and loss.TiC particles can play a "skeleton" role under the impact effect,which can slow down the impact effect of abrasive and reduce the material spalling and loss.Therefore,the new wear-resistant steels Ti20 and Ti60 show better impact abrasive wear performance than the commercial steel JFE400 in the environment with low gangue content(dry coal not doped with quartz sand).In addition,the hard phase Ti C significantly hinders the ploughing behavior of the abrasive,so the new wear-resistant steels Ti20 and Ti60 exhibit better impact abrasive wear performance than the commercial steel JFE400 in the environment with high gangue content(dry coal doped with 40 wt.% quartz sand)In impact abrasive wear,Ti C will also protrude from the matrix due to galvanic corrosion with the matrix and hinders the ploughing behavior of coal,but also the coupling effect of high gangue content and acid corrosion(coal doped with 40 wt.% quartz sand and then doped with 20 wt.% acid mine water simulation fluid)will reduce the wear performance of the new wear-resistant steel.However,under different simulated conditions,the impact wear resistance of the new wear-resistant steels Ti20 and Ti60 are better than that of the commercial steel JFE400.(4)The new wear-resistant steels Ti20 and Ti60 are suitable for the parts with medium and high gangue content and no acid corrosion condition or low gangue content and acid corrosion condition with three-body abrasion.Or applied to different working conditions of impact abrasive wear parts.