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首页> 外文期刊>Materials Science and Engineering >Strengthening mechanisms and creep rupture behavior of advanced austenitic heat resistant steel SA-213 S31035 for A-USC power plants
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Strengthening mechanisms and creep rupture behavior of advanced austenitic heat resistant steel SA-213 S31035 for A-USC power plants

机译：A-USC电厂用高级奥氏体耐热钢SA-213 S31035的增强机理和蠕变断裂行为

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摘要

A newly advanced heat-resistant steel SA-213 S31035 (22Cr25Ni3W3CuCoNbN), is currently the strongest commercially available austenitic heat resistant steel and has been recognized as one of the main candidate materials for A-USC plants operating at 700 ℃. Up to now, the reason for which has excellent creep performance is not clear yet. In this paper, the S31035 steels were crept at 700 ℃ with applied stresses in the range of 140-220 MPa up to 15627 h, and during creep the microstructure evolution including the precipitation of second phases as well as their strengthening mechanisms were deeply investigated. Creep tests results show that S31035 steel has much higher creep strength than S30432 steel, with extrapolated creep rupture strength of about 118.0 MPa at 700 ℃ for 50,000 h. Furthermore, it has great rupture ductility with an area reduction of more than 50%. The excellent creep strength of S31035 steel was produced by the combined precipitation strengthening of nano-scaled Cu-rich phase, needle-shaped Laves phase, and secondary Z phase. The nano-scaled Cu-rich phase was very stable during long-time creep and acted as the dominant precipitation strengthening. Unlike the coarse and granular Laves phase in ferritic P92 steel (9CrW), the spindly needle-shaped Laves phase in austenitic S31035 steel could effectively impede the moving of dislocations and greatly increase the creep strength. And the coarsening of Laves phase in width was slight but in length was apparent, which was conducive to the strengthening effect. The fine secondary Z phase also showed relatively slow coarsening rate, contributed an Important part of strengthening enhancement. The precipitation of detrimental a phase is effectively suppressed through the increased content of Ni and the addition of Co. Besides, the grain-boundary sliding and grain rotation occurred during creep. Under high stresses (≥170 MPa) and short-time creep, intragranular cracks dominated the creep failure. The cracks preferred to produce inside the grains with higher Taylor factor which are hard to deform. Under relatively lower stresses (≤140 MPa), intergranular cracks dominated the creep failure and cracks mainly generate on the grain boundaries between the grains with greatly different deformations. The texture <111>//RD formed during creep, suppressing the proceeding plastic deform and improving the creep resistance. Under lower stress and long-time creep, a new texture <001>//RD occurred, which improves the creep rupture ductility of the S31035 steel.
机译：一种最新先进的耐热钢SA-213 S31035（22Cr25Ni3W3CuCoNbN）是目前市场上最坚固的奥氏体耐热钢，并且被公认为是在700℃下运行的A-USC工厂的主要候选材料之一。到目前为止，尚不清楚具有优异蠕变性能的原因。本文对S31035钢在700℃蠕变，施加应力140-220 MPa达15627 h进行了蠕变，并对蠕变过程中包括第二相的析出及其强化机理进行了深入研究。蠕变测试结果表明，S31035钢比S30432钢具有更高的蠕变强度，在700℃下50,000 h的外推蠕变断裂强度约为118.0 MPa。此外，它具有很大的断裂延展性，面积减少了50％以上。 S31035钢具有优异的蠕变强度，是通过纳米级富铜相，针状Laves相和Z次生相的沉淀强化相结合而获得的。纳米级富铜相在长时间蠕变过程中非常稳定，并起着主要的沉淀强化作用。不同于铁素体P92钢（9CrW）中的粗大和颗粒状的拉夫斯相，奥氏体S31035钢的刺状针状拉夫斯相可以有效地阻止位错的移动并大大提高蠕变强度。拉夫斯相在宽度上的粗大化很小，但在长度上却是明显的，这有利于增强效果。细化后的Z相也显示出相对较慢的粗化速率，是强化强化的重要部分。通过增加Ni的含量和添加Co，可以有效地抑制有害a相的析出。此外，蠕变过程中发生了晶界滑动和晶粒旋转。在高应力（≥170MPa）和短时蠕变下，晶粒内裂纹占主导地位的蠕变破坏。裂纹倾向于在泰勒系数较高的晶粒内部产生，且难以变形。在相对较低的应力（≤140MPa）下，晶间裂纹占蠕变破坏的主要部分，裂纹主要产生在晶粒间的晶界上，且形变差异很大。蠕变期间形成的织构<111> // RD，抑制了正在进行的塑性变形并提高了抗蠕变性。在较低的应力和长时间的蠕变下，出现了新的织构<001> // RD，从而提高了S31035钢的蠕变断裂延性。

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