| 304 stainless steel is widely used in marine environments with harsh corrosive environments.In order to further improve the use range of 304 stainless steel,improve its hardness and wear resistance,and improve the corrosion resistance of 304 stainless steel.It can adapt to the harsh working environment and improve its working ability and service life.It can be treated with surface modification,and the hardness,friction,corrosion resistance and other properties of the surface of the component can be greatly improved through surface modification.In this thesis,304 stainless steel was taken as the research object,and Febased amorphous alloy coating and Co-based alloy coating were prepared on the surface of 304 stainless steel by laser cladding technology to study its modification.The crack failure mechanism of Fe-based amorphous alloy coating was analyzed,and the modification mechanism of Co-based alloy coating on the surface hardness,wear resistance and corrosion resistance of 304 stainless steel was analyzed.Hardness and wear resistance of alloy coatings.The contents and results of the research are as follows:(1)Crack analysis of Fe-based amorphous alloy coating: The Fe-based amorphous alloy coating was prepared on the surface of 304 stainless steel substrate by laser cladding technology.Qualitative analysis,the coating structure and crack forming mechanism were studied,the research showed that the crack was mainly caused by the large thermal stress in the heat affected zone and the high melting point and high hardness carbon silicide segregated by C and Si elements,near the crack zone.The structure was relatively loose and there were many gaps and pores,and the combination of hardness was not strong,so that the hardness near the crack zone was lower than that of other defect-free places at the same level.(2)The corrosion resistance of Co-based alloy coatings was studied: after electrochemical corrosion,the self-corrosion potential of the coating-504.5m V was more positive than the self-corrosion potential of 304 steel-579.7m V.The surface of the coating showed mild corrosion points,and severe corrosion occurred on the surface of 304 steel.It shows that Co-based alloy coating can effectively improve the corrosion resistance of 304 stainless steel surface.(3)The hardness and wear resistance of Co-based alloy coatings were studied:Co-based alloy coating had a greater increase in surface hardness and better wear resistance than 304 stainless steel.The average wear amount of the cladding layer at 10 N,30N,90 N,and 150 N was analyzed to be 5.4,14.7,62.9,and 156.5 mg,respectively.It can be seen that the greater the load,the greater the shear stress in the contact area during the wear process.The temperature rises significantly,which makes the sample more prone to plastic deformation and increases the amount of wear.Under the action of large loads of 90 N and 150 N,peeling and sticking appeared at the bottom of the specimen.(4)Research on post-coating treatments: Co-based alloy coatings prepared on the surface of 304 stainless steel were aged at 850 °C for different time periods.The study revealed the changes in the microstructure and properties of Co-based alloy coatings under different aging times.The results showed that: The precipitates in the coating were mainly carbides,and their growth and distribution had changed under different time periods.The hardness and wear resistance of the coating were greatly improved after aging for 8 hours. |
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