| The coating structure obtained by atmospheric plasma spraying(APS)is granular structure or lamellar structure,which is formed by the deposition and stacking of individual powder particles.In recent years,low pressure plasma spraying(LPPS)technology has become a new research hotspot.Due to its low pressure working environment,equiaxed grains microstructure coating which is different from traditional coating microstructure can be obtained.The coating properties can be improved and have a good application prospect.316L stainless steel powder was selected as the material and sprayed by low-pressure plasma spraying.By changing the spraying conditions and heat treatment conditions,the coating of different structures was obtained,including traditional coating structures of granular structure and lamellar structure,and equiaxed grains structure.The results showed that both high plasma spray energy and heat treatment can promote the formation of equiaxed grains structure,and with the increase of heat treatment temperature and heat preservation time,grain size of equiaxed grains grew.The microstructures showed that the equiaxed grains microstructure is denser than the traditional coating microstructures.However,the microhardness of the original coating was higher than that of the equiaxed grains coating,and with the increase of heat treatment temperature,the microhardness of the equiaxed grains structure showed a declining trend until the complete formation of equiaxed grains structure.The equiaxed grains coating had much better corrosion resistance than traditional microstructure coatings from the result of immersion test.XRD results showed that the equiaxed grains structure does not contain the ferrite phase,only made up of the austenite phase,which affected the corrosion resistance of different coatings.The tensile strength of coatings with different microstructure were measured by tensile test.It was found that tensile strength of equiaxed grains coatings after 1100? and 1200? heat treatment were 447MPa and 471 MPa,which were much higher than that of granular coating(71 MPa)and lamellar coating(92 mpa).The elastic modulus of coatings decreased gradually with the increase of heat treatment temperature,but were higher than the original coating structure.The results of scanning electron microscopy(SEM)showed that the fracture mode of the equiaxed grains was ductile fracture,while the traditional coatings were brittle fracture.,which was consistent with the stress-strain curve.Compared with the cast 316L stainless steel structure material,the equiaxed grains structure coating is more similar in properties than the traditional coatings. |
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