对650℃,100 MPa条件下蠕变1546.5 h的P92钢试样进行了组织热损伤及应变损伤观察,分析了蠕变孔洞形成机理.结果表明,分布于板条间的M_(23)C_6相的粗化不明显,保持较高的数量密度,晶界上粗大的M_(23)C_6相大部分消失,导致其体积分数明显减少.在晶界上析出密集分布的的Laves相,平均等效直径为320 nm,体积分数约为2.6%.在晶界上形成了单个分布的蠕变孔洞.蠕变孔洞的形成与晶界上析出Laves相密切相关.由于Laves相分布于晶界,其沉淀强化作用不大,使基体合金元素贫化,促进蠕变孔洞的形成而降低P92的蠕变断裂强度.要进一步提高新型马氏体热强钢蠕变性能的关键是抑制Laves相在晶界的析出.
The thermally and strain induced damage of P92 (9Cr-0. 5Mo-1. 8W-VNb) steel were investigated after creep test conducted under an applied stress of 100 MPa for 1546. 5 h at 650℃ ,and the mechanism of creep damage waa examined. The results show that M_(23) C_6 carbide located on subgrain boundaries maintains with fine and high densitiy distribution during the creep,but most of the relative large M_(23)C_6 particles located on grain boundaries disappears ,which results in the considerable reduction in volume fraction of M_(23)C_6. The Laves phase with the mean diameter of about 320 nm and the volume fraction of 2. 6 % is precipitated along grain boundaries after creep test. A few sparsely distributed voids nucleated at the Laves phase form along grain boundaries. The Laves phase distributed along grain boundaries can not contribute to the precipitation hardening,but leads to the decrease of the creep rupture strength due to providing cavity nucleation sites. The creep properties of P92 steel can be improved by retarding and avoiding the formation of Laves phase along grain boundaries.
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