一级应变硬化F316奥氏体不锈钢的高温蠕变性能

研究了在200 MPa应力下一级应变硬化F316奥氏体不锈钢在650℃、680℃和700℃的蠕变性能和蠕变断裂行为。结果表明： 在200 MPa 恒定应力下蠕变温度越高其蠕变寿命越短,稳态蠕变速率越大,由应力加载引起的瞬时应变越大。蠕变断裂方式主要为韧性断裂。蠕变孔洞主要分布在三叉晶界等脆弱部位,距离断口越远试样中孔洞的平均尺寸和孔洞面积百分比越小。在与断口距离相同的位置上,随着蠕变温度的提高蠕变孔洞的平均尺寸和面积百分比均明显增大。与未预应变的F316不锈钢相比,具有高密度孪晶的一级应变硬化F316不锈钢具有更大的蠕变抗力。分别基于Larson-Miller 参数法和θ参数法外推计算了350℃/200 MPa下的蠕变寿命,θ参数法的拟合曲线与实际蠕变曲线吻合得较好。根据Larson-Miller参数法和θ参数法,探讨了350℃/200 MPa下一级应变硬化F316奥氏体不锈钢长期服役蠕变可靠性。

Creep Properties of Pre-deformed F316 Stainless Steel

Creep properties of the pre-deformed F316 stainless steel by 200 MPa at 650℃, 670℃ and 700℃ were investigated. Results show that by a constant tensile stress of 200 MPa, the time to rupture of the pre-deformed F316 stainless steel decreases, while the steady creep rate and the instantaneous creep strain increase with increasing creep temperature. Ductile fracture is the dominant rupture mode for the pre-deformed F316 stainless steel. Creep cavities are mainly located in the triple junctions of grain boundaries, and the average diameter and the area ratio of the voids decrease in the location with the increasing distance to the fracture surface. In the region with the same distance to the fracture surface, the average diameter and area percentage of the voids increase obviously with the increasing creep temperature. The present pre-deformed F316 stainless steel with high density of twins has a better creep resistance than that of non-pre-deformed ones. Time to rupture by 200 MPa at 350℃ was estimated by using the Larson-Miller and θ-projection methods, respectively. The results show that the θ-projection method can give a better correlation. Besides, the long-term creep reliability of the F316 stainless steel served by 200 MP at 350℃ was discussed based on the Larson-Miller and θ-projection methods.