Research On Heat Treatment Process Of 13 Cr Super Low Carbon Martensite Stainless Steel And Its Laser Surface Modification

Based on the characteristics and development direction of propeller material in polar waters,this paper choosed 00Cr13Ni4Mo super low carbon martensitic steel as the research object.The effects on heat treatment upon the microstructure,the product of strength and elongation,electrochemical corrosion resistance of 00Cr13Ni4Mo were studied.The Strengthened surface was used to improve the fatigue life,wear resistance and electrochemical corrosion resistance of stainless steel with laser treatment.And the purpose is to provide the basis for the development of propeller materials in polar waters.Through the experimental study and analysis,the following conclusions were drawn:?1?After two-stage tempering,the content of the reversed austenite is increased.The reason is that tempering of test steel at 680?precipitates a certain amount of carbide and refines lath martensite for the austenite to provide the positions of the nucleation and the driving force of nucleation.In the second tempering process,with the increase of holding time,the content of reversed austenite increases,and the product of strength and elongation of the steel is slightly changed between 19711MPa%and 20232 MPa%.During two tempering,a large amount of Cr carbide was precipitated at 680?,and the precipitation of carbides increased with the increase of the holding time at 620?.However,due to the further increase of reversed austenite,electrochemical corrosion resistance was not fall.The formation of reversed austenite enriching austenitized element Creduces the formation of carbides that improves the poor Cr region and the symbiotic relationship with the carbide also improves the defect point.?2?Electrochemical corrosion resistance of the test steel after the melting treatment was greatly improved.The main reason is that the microstructure from two-phase into a single martensite greatly,no micro-component segregation,carbide too late to precipitate reduce the formation of micro-primary battery.?3?After strengthening the surface with laser melting,fatigue crack growth rate decrease and fatigue performance improved.As the laser power increases,the fatigue crack propagation rate decreases.The main strengthening mechanism:dislocation strengthening,solid solution strengthening,fine grain strengthening and the presence of surface compressive stress.After the melting treatment,the wear weight loss reduced by1/6 less than that of the substrate.?4?Laser cladding CoCr-WC,cladding layer is composed of the network dendrites of CoC_x,Cr₂₃C₆ and WC_1-x-x interpenetrating growth and intergranular of solid solution Co.After adding Ta powder,cladding layer generate a new phase Co₃Ta,Ta₄C_3.04,Ta₇W₃C₁₀,and Ta₇W₃C₁₀0 and Ta₄C_3.04.04 are precipitated in a short rod shape.When Ta content is 15%,the precipitated shape of Ta₇W₃C₁₀0 and Ta₄C_3.04.04 changes from short rod to chrysanthemum.?5?The addition of 5%Ta does not increase the wear resistance of the cladding layer compared wtih the without adding Ta.the main reason is that Ta react with WC which produces Ta₄C_3.04.04 and Ta₇W₃C₁₀0 reducing heterogeneous core,and the decreased nucleation rate leads to tissue coarsening reducing hardness significantly.As the content of Ta increased,the cladding layer hardness increased to improve the wear resistance.The addition of 15%Ta reduces the wear weight loss by 1/3 compared with not adding Ta of the cladding layer,which is only 1/17 of that of the matrix compared with the matrix.The main reason is that increasing the content of Ta enhances Co solid solution strengthening effect and dispersion strengthening effect which the content of Ta₄C_3.04.04 and Ta₇W₃C₁₀increased.The strengthened matrix can support the hard phase and cutting wear resistance better.