Microstructure and cavitation erosion resistance of 304 stainless steel after laser cladding of iron-based alloy on its surface
JIN Feng
ZHANG Song
WANG Li
WU Chenliang
HUO Sha
Abstract：[Objective]304 stainless steel is a chromium-nickel stainless steel with austenite as the main crystal structure.It is widely used in the aerospace,marine,and chemical industries for its excellent heat and corrosion resistance.However,its hardness is low,and its cavitation erosion resistance is poor.When it is used as a material for turbine blades,exposure to complex environmental conditions leads to surface pitting and spalling,which severely shortens the service life of the blades.[Methods]To enhance the service life of 304 stainless steel,a novel iron-based alloy cladding layer was fabricated on its surface by using laser cladding.The obtained iron-based alloy cladding layer was subjected to phase analysis,microstructural observation,EBSD analysis,hardness testing,and cavitation erosion testing to analyze its phase composition,crystallographic characteristics,microhardness,and cavitation erosion resistance.[Results]The results show that the iron-based alloy cladding layer is mainly composed of α-Fe phase and Cr23C6 phase.The cladding layer has good forming quality without microcracks and with only a few pores.The microstructure of the cladding layer shows typical non-equilibrium solidification structure characteristics,which is composed of dendrites and interdendritic network structures,showing the morphologies of planar crystals,cellular crystals,columnar crystals,and equiaxed crystals from the bottom region to the top region.The EBSD results show that high-density grain boundaries were formed in the cladding layer and no obvious texture was formed.The cross-sectional microhardness of the cladding layer fluctuates between 640 HV0.2 and 750 HV0.2,which is considerably higher than the microhardness of the 304 substrate(187.6 HV0.2).The higher microhardness of the cladding layer is attributed to solid solution strengthening,the second phase strengthening by Cr23C6 and Cr7C3 hard phases distributed among cellular dendrites,and grain boundary strengthening brought by high-density grain boundaries.The cumulative mass losses of the 304 substrate and the iron-based alloy cladding layer after cavitation erosion test for 300 min are 24.8 mg and 7.8 mg,respectively.The mass loss of the iron-based alloy cladding layer is about 31.5％of that of the 304 substrate.During the whole cavitation erosion test,the cumulative mass loss of the iron-based alloy cladding layer is less than that of the 304 substrate.The surface analysis results after the cavitation erosion test show that the shear waves generated by the collapse of bubbles can cause stress accumulation on the surface of the material,thereby promoting the formation of slip bands.Cracks are prone to generation and expansion on the slip bands,eventually leading to material spalling and forming cavitation pits.Small grain sizes,a high grain boundary density,and high microhardness are the key reasons for the excellent cavitation erosion resistance of the cladding layer.[Conclusion]The higher microhardness of iron-based alloy cladding layer significantly improves the cavitation erosion resistance of the 304 stainless steel substrate.In this study,a high-microhardness iron-based alloy cladding layer for surface modification of 304 stainless steel was designed and prepared to promote the application of laser cladding technology in the reinforced coatings for turbine blade surfaces to a certain extent.
Keywords：laser cladding technology304 stainless steeliron-based alloyphase analysismicrostructuretexturemicrohardnesscavitation erosion resistance
Publication Date：2025-07-25
Online Publishing Date：2025-09-18(First online date of this platform, not the publication date of the document)
Pages：8( 530-537 )