Research On Siliconized Layer And High Temperature Corrosion Capability Of Austenitic Stainless Steel

A fine and dense siliconized layer was obtained on the 0Cr18Ni9 austenitic steel by pack cementation.The siliconized layer could be obtained at 1050℃for 4 hours. Using the scanning electronic microscope(SEM) and the X-ray energy dispersive spectrum(EDS) and XRD,the composition,microstructures and morphologies of the siliconized layer were analyzed.The oxidation behavior of the layer was investigated by high temperature oxidation test at 600℃for 100 hours and 250 hours and at 900℃for 100 hours,and the role of the silicon is also investigated.After high temperature oxidation the increased weight was tested at different times on siliconized and original samples.According it,the oxidation kinetics was charted.The kinetic analysis of the coating was done by the oxidation kinetics.The siliconized layer had better oxidation resistance than the original austenitic steel which can be observed through kinetics. The siliconized stainless steel and original stainless steel were carburized at 930℃at different time,and the effect of siliconized on stainless steels to high temperature carburize was analyzed.It was found that the phase constituent was Fe₃Si in the layer.There were double layers in the coating,and the outer layer was silicon-rich phase,the other was siliconized layer.The siliconized layer had good combination with the austenite substrata.The layer included spinodal decomposition microstructure and high-Si phase.The intensity of the siliconized layer was tested by micro hardness.An artificial fracture test was conducted in order to detect the combination between the siliconized layer and the steel matrix.The result revealed that the siliconized layer had good combination with the austenite substrata,and the morphology of the fracture was related with the silicon gradient in the layer.It was found that oxidation kinetics curve obeys the parabolic law.The kinetics curve ascended slowly at 600℃.The weigh gain of siliconized was much lower than the original austenitic steel,the anti-oxidizing resistance attributed absolute anti-oxidizing.The fine crystal reached nanometer,the active function of grain boundary and the dense SiO₂ oxide film could enhance anti-oxidizing.Analyzed oxide of surface reveals that the oxide distributed equably and anti-oxidizing resistance was fine.Si prevented C atom from infiltration.The siliconized stainless steels had better behavior of carbonization resistance.