| 300M steel has the advantages of high strength,good toughness,excellent fatigue properties,which is the main landing gear steel,but 300M steel is easy to be corroded when it worked in a corrosive environment.In addition,in the inherent contact of the landing gear,there is a higher requirement for the performance of steel,such as hardness and wear resistance.To solve the above problems,in this paper,ion implantation technology was applied to prepare Cr modification layer on the surface of 300M steel and explored its corrosion and wear resistance.In this subject,five different kinds of ion implantation dosages were selected,the five doses were2.38×1016?4.77×1016?9.50×1016?1.40×1017?2.80×1017 ions/cm2 respectively.The Trim2008 program was used to simulate the ion implantation process.It was found that the depth of ion implantation was 45nm,and the content of Cr elements was the highest at 18.2nm.Through scanning electron microscope,the scratch on the surface of the sample decreased and the scratch depth became shallow,and the surface was more smooth after ion implantation.The XRD phase showed that the surface of the sample appeared saturated solid solution and some compounds.The solid solution enhancement of ion implantation improved the surface strength of the sample.As the bombardment of ion implantation,the surface roughness of 300M steel decreased.However,with the increase of ion implantation dose,the surface roughness of matrix increased.When the ion implantation dose was 4.77×1017 ions/cm2,saturated solid solution was produced on the surface of the sample.The microhardness of the modified layer was 829.3 HV0.05,which was 58%higher than that of the matrix(523.2 HV0.05),and its nano hardness was 761.4,which was 50.4%higher than that of the substrate.The modulus of elasticity of modified laye reached 272Gpa far higher than the 176GPa of the matrix.Neutral salt fog and electrochemical test were carried out to study corrosion resistance of modification layer with Cr ion injection The neutral salt spray test of 100h showed that the corrosion resistance of the modification layer was much higher than that of the matrix.The Cr element produced a compact passivation film to protect the matrix.In electrochemical test,modification layer corrosion potential was significantly higher than substrate;coating capacitance arc amplitude was larger than matrix.When the ion implantation dose was 4.77×1016 ions/cm2,the corrosion resistance of the modification layer was the best,and the self corrosion potential was-0.084V far higher than the-6.97V of the matrix.Reciprocating friction resistance experiments were carried out to study the wear resistance in different dose,load and speed.The results showed that the friction coefficient of the 300M steel was about 0.8,and the friction coefficient of the modified layer was about 0.2.The wear rate was 0.1487×10-44 mm3·m-1,when the load was 220g the sliding speed was 3m/min and the dose was 4.77 x1016ions/cm2 which was 3%of 300M.The matrix produced more serious wear and tear due to the increase of speed and load,but little effect on the Cr modification layer.When the modification layer was damaged,sample had higher wear resistance than the substrate,because Cr element would diffuse along the high density dislocation which produced by the ion implantation.Therefore,the Cr element diffused continuously with the friction and wear,which greatly improved the wear resistance of the 300M steel. |
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