| High carbon martensitic stainless steel has become the main raw material of high-end cutlery due to its high hardness,good wear resistance and moderate corrosion resistance.The domestic knife and scissors industry is facing a strategic need for transformation and upgrading,and the high-end cutlery steel market capacity and potential demand are large.However,currently high-end cutlery steels are mainly imported due to few domestically-available cutlery steels.The reason is the lack of systematic research on domestic cutlery used high-carbon martensitic stainless steel,which results in insufficient innovation of high-quality cutting tools.Therefore,it is necessary to carry out a systematic comparative investigation of the microstructure and performance characteristics of various domestic high-carbon martensitic stainless steels.This topic can provide data and theoretical support for the optimization of the performance of domestic steel products for cutting tools and the development of new products,and it is conducive to promoting the development of the cutting industry.The microstructure and properties of high-end cutlery used high-carbon martensitic stainless steels(5Cr15MoV,7Cr17 MoV,9Cr14 MoV and 9Cr18 MoV)are investigated systematically in this paper,and the effect of carbide dissolution on performance is emphasized.In addition,the microstructure,wear resistance,corrosion resistance and antibacterial properties of the novel cutlery used martensitic stainless steel 6Cr16 Mo MA(751M)are studied,and compared the microstructure and performance with 5Cr15 MoV and 9Cr18 MoV.The main results are as follows:(1)Through systematic analysis of the microstructure and mechanical properties of four high-carbon martensitic stainless steels,it is found that the dissolution of carbides could be divided into three stages and correspond to the mechanical properties:(i)small-sized secondary carbides(< 0.5μm)are rapidly dissolved.Since the strengthening effect of martensite matrix is greater than the softening effect caused by the increase of volume fraction of retained austenite(RA),the hardness increases significantly.(ii)dissolution of large-sized secondary carbides(<1μm)become dominant,increasing the toughness due to the increase of RA volume fraction.(iii)secondary carbides with the sizes ranging between 1–5μm begin to dissolve.Accordingly,the toughness continues to increase,and the hardness reduces drastically due to the high RA volume fraction.(2)The dissolution behavior of carbides in high carbon martensitic stainless steels is investigated.It is found that at a lower austenitizing temperature,the Cr / Fe(wt.%)of small-sized carbides is smaller than that of large-sized carbides.It shows that small-size carbides are more soluble than large-size carbides.This phenomenon is mainly related to the diffusion distance of the elements in the carbide,the interfacial energy between the carbide and the matrix,and the directionality of the carbide dissolution.(3)The relationship between the microstructure and properties of self-developed 751 M is studied.Compared with 5Cr15 MoV and 9Cr18 MoV,751 M has high hardness while still having excellent impact toughness.The fine and evenly distributed carbides in 751 M give it a higher hardness and excellent wear resistance.The corrosion performance comparison studies show that 751 M has the smallest corrosion current density,the highest pitting potential and the lowest salt spray corrosion rate.Due to the addition of Ag element,751 M has excellent antibacterial properties.The antibacterial rates against Escherichia coli,Gluconococcus aureus,Candida albicans and Pseudomonas aeruginosa are all above 99%.It shows that the self-developed high carbon martensite stainless steel 751 M is more suitable for the production of high-end tools.(4)In order to further improve the performance of 751 M,cyclic annealing and thermal compression technology are used to explore the effect of its microstructure control. |
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