| The cross shaft is a force transmission component used to connect the rocket body and the engine,which can ensure the rocket's attitude control?pitch,yaw,etc.?smoothly in the air,so it has an important impact on the normal operation of the rocket.However,the cross shaft works in a high-speed and heavy-load service environment.It has the characteristics of large axial load and radial load change direction.These severe conditions place high requirements on the performance of the cross shaft.Based on this background,this article uses ion implantation technology to prepare a modified layer on the surface of 300M steel?cross shaft material?,and designs three implantation processes:N-implantation,Ti-implantation,and N+Ti-implantation.Different implant doses to analyze the degree of strengthening of the substrate by different implant processes,and the effect of different implant doses on the substrate performance under the same implant process.The process of implanting N and Ti ions into 300M steel was simulated by SRIM2008,and the implantation dose and energy for each implantation process were determined.The maximum depth of the two ion implantations was 190 nm and 50 nm,respectively.They all show a Gaussian distribution inside the matrix and cause a lot of lattice damage.Using OM,SEM,XRD,EDS and other testing methods to analyze the surface morphology and composition of the modified layer,the results show that the300M steel matrix is mainly a martensite structure containing?Fe,Ni?phase.New phases of Cr2N and Fe3N are formed on the surface of the N-implanted sample,which plays a role of solid solution strengthening.Ti O2 is formed on the surface of the Ti-implanted sample,which has abrasion-reducing effect.The surface of the N+Ti-implanted sample contains not only nitrides and Ti oxides,and the second strengthening phase Ti N is formed.Ion implantation has a smoothing effect on the surface of the sample,and the scratches on the surface of the 300M steel after implantation are reduced and shallow,especially when N+Ti is implanted,and with the implantation The greater the dose,the more obvious the effect.The mechanical properties of the substrate and the modified layer were tested using a micro-vickers hardness tester and a nano indenter.The test results show that with the same implantation process,as the implant dose increases,the mechanical properties also gradually improve,and the dual element implantation N+Ti process has the most obvious improvement.When the doses of N and Ti are 2×1017ions/cm2 and 1×1017ions/cm2,respectively,the microhardness increased by 41.2%,and the nanohardness and elastic modulus increased by 79.26%and 34.73%relative to the matrix,respectively.Through reciprocating friction and wear experiments,it was found that the retention time of the modified layer increased with the increase of the implantated dose,and the implantation sample was less abraded than the substrate.In the same implantation process,the greater the implantation dose is,the smaller the wear is.Under the dual-element of N+Ti implantation process,when the N implantation dose is 2×1017ions/cm2,the Ti implantation dose is 1×1017ions/cm2.The effect is most obvious,the amount of wear is reduced by 87%compared to the substrate.The matrix was initially dominated by adhesive wear,and then gradually transitioned to three-body abrasive wear.The low friction coefficient of the N-implantated sample was mild abrasive wear and adhesive wear.After the modified layer was damaged,the wear increased and the friction coefficient increased.The wear mechanism of Ti-implantated samples is similar to that of N-implantated samples,but the titanium oxide layer on the surface makes the modified layer longer than the N-implantated samples.The N+Ti-implantated sample has both the high hardness of the N-implantated sample and the titanium oxide lubricating layer of the Ti-implantated sample,so its wear resistance is best. |
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