| Super304H austenitic stainless steel is used as ultra-supercritical boiler superheater steel tube for its excellent stability of hot strength, anti-corrosion and oxidation resistance, and its high creep rupture strength. However, it still needs study on aging precipitation behavior and the effect of aging treatment on its performance because its service conditions are very bad in the practical production. This paper studies not only the initiale state of Super304H austenitic stainless steel but also aged at 750℃and 800℃. We analyses the morphology, distribution and size of precipitated phase by the observation of aging and microstructure under 750℃and 850℃in different time. And microstructure is studied by metalloscope, scan electron microscope, electronic probe and transmission electronic microscopy. We also analysis its component and crystal structure by analysis of precipitation phase with electron diffraction technique and X-ray energy spectrum. By measuring the hardness value of sample mentioned before with microhardness tester, the experiment comes to the main conclusion as below:With the extend of time,the grain size of Super304H austenitic stainless steel has less changes but more precipitation phase gradually. With the rising of the aging temperature, precipitation phase decreases but size increases. It can get M23C6 carbide particles at the place of grain boundary. Besides M23C6 carbide particles and NbCrN, they are mainly face-centered cubic NbC. The hardness value of Super304H austenitic stainless steel is high. The higher temperature is, the lower hardness value is. But with extend of aging time the hardness value has no obvious changes.
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