Abstract In this study, the effect of the tool rotational speed on the microstructure evolution and its significance on the mechanical properties of friction stir welded 9Cr-1Mo (P9) steel is investigated, and its properties are compared with A-TIG welding process. Friction stir welding (FSW) was carried out at two different rotational speeds viz., 200 rpm and 500 rpm with the constant traverse speed of 30 mm/min using the W-La2O3 tool. The consequence of this study showed that irrespective of tool rotational speed, the better tensile properties are achieved by the FSW process, and it is comparable to the A-TIG welded joint. This study proved that FSW is a potential welding technique for welding of P9 steel, and also, there is scope to avoid PWHT by lowering the tool rotational speed (

中文翻译：

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刀具转速变化对搅拌摩擦焊9Cr-1Mo钢组织演变的响应及其对力学性能的影响

摘要 本研究研究了刀具转速对搅拌摩擦焊9Cr-1Mo（P9）钢组织演变的影响及其对力学性能的影响，并将其性能与A-TIG焊接工艺进行了比较。搅拌摩擦焊 (FSW) 使用 W-La2O3 工具在两种不同的转速下进行，即 200 rpm 和 500 rpm，恒定横向速度为 30 毫米/分钟。这项研究的结果表明，无论工具转速如何，FSW 工艺都能实现更好的拉伸性能，并且与 A-TIG 焊接接头相当。该研究证明FSW是一种潜在的焊接P9钢的焊接技术，并且通过降低工具转速有避免PWHT的空间。