Shot peening is currently utilized in coal-fired power plant components to mitigate scale exfoliation issues from steamside oxidation of austenitic stainless steel superheater and reheater tubing. To focus on commercially available material, this study exposed quarter-ring specimens cut from two different commercially shot peened type 304H tubes and exposed to 1 bar steam for up to 15,000 h at 550°, 600°, 625°, and 650 °C. Specimens were removed at increments to characterize the oxide thickness and microstructure. The shot peened inner surface generally retained a thin, protective Cr-rich scale with occasional Fe-rich oxide nodules at 550–625 °C. The increased oxidation resistance from shot peening began to degrade at 650 °C after as little as 5,000 h. Cut and polished faces of these specimens formed thick, Fe-rich oxides similar to polished 304H coupons. Surprisingly, the mechanically machined outer surface of the tube specimens performed similarly to the shot peened inner diameter, suggesting it had sufficient cold work to achieve a similar benefit. Electron backscatter diffraction and Vickers-hardness measurements were used to characterize post-exposure changes in underlying microstructure and mechanical properties, respectively, imparted by shot peening.

中文翻译：

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喷丸强化对304H不锈钢蒸汽氧化的影响

喷丸处理目前用于燃煤电厂部件，以减轻奥氏体不锈钢过热器和再热器管的蒸汽侧氧化引起的水垢剥落问题。为关注市售材料，本研究对从两个不同的商用喷丸 304H 管切割的四分之一环样品进行了暴露，并在 550°、600°、625° 和 650°C 下暴露于 1 bar 蒸汽中长达 15,000 小时。以增量方式移除样品以表征氧化物厚度和微观结构。在 550-625 °C 时，喷丸处理的内表面通常会保留一层薄的、具有保护性的富铬氧化皮，偶尔会出现富铁氧化物瘤。喷丸增强的抗氧化性在 650 °C 时仅在 5,000 小时后开始下降。这些试样的切割和抛光面形成厚厚的，类似于抛光的 304H 试样的富铁氧化物。令人惊讶的是，管试样的机械加工外表面与喷丸内径相似，表明它有足够的冷加工来实现类似的好处。电子背散射衍射和维氏硬度测量分别用于表征由喷丸赋予的潜在微观结构和机械性能的暴露后变化。