Development of Ni-base Rought Alloy for Nuclear Heat Exchanger, Excellent in Phase Stability at High Temperature

高温相稳定性优异的核热交换器用镍基粗合金的开发

基本信息

批准号：
62850133
负责人：
KIKUCHI Makoto
金额：
$ 4.61万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

项目摘要

Creep properties and microstructure of Ni-2OCr-Nb-W alloys containing variable amounts of niobium and tungsten were investigated at 900 and 1,000ﾟC, focusing on a role of grain boundary precipitates. The alloys with higher niobium content. In which the Widmanstatten type beta-Ni_3Nb phase precipitates after its precipitation at grain boundaries, showed a relatively small minimum creep rate at 900ﾟC, accompanied by the degradation of rupture elongation. The effect of time lag between the in-grain and grain boundary precipitations of the beta-phase on creep resistance of the alloy was evaluated by observing their creep rate-time curves. When the tungsten content of a Ni-2OCr-3Nb-l3W alloy increased up to 17 wt%, marked improvement of creep properties was found under lower stress levels and it is strongly correlated to the grain boundary precipitation of the alpha_2 W-phase which occurs after that of the beta-phase. It is concluded that the grain boundary precipitation strengthening effect due to such dual phases as beta and alpha_2, is one of the most effective methods for improving the creep strength.In order to make the high temperature creep strength of Ni-Cr-Nb-W type alloys higher, the effects of boron and zirconium on creep properties in high-purity Ni-2OCr alloys were investigated. By the boron and zirconium addition, creep resistance, rupture life and rupture elongation of a Ni-20Cr alloy were improved. The longer rupture life and larger rupture elongation with the addition of boron or zirconium would be caused by the formation of subgrains and dynamic recrystallization which retard the initiation and propagation of grain boundary aracks.The possibility of the development of a new alloy for nuclear heat exchanger with far higher creep rupture strength than several candidate alloys ( Ni-Cr-W type alloys ) was suggested.

在900和1,000°C时研究了含有可变量的niobium和Tungsten的Ni-2ocr-NB-W合金的蠕变性质和微观结构，重点是晶粒边界沉淀的作用。具有较高氮化物含量的合金。其中widmanstatten型β-NI_3NB相在晶界下沉淀后沉淀，显示了900 c时相对小的最小蠕变速率，通过破裂伸长的降解来实现。通过观察其蠕变速率时曲线，评估了β期的元素内和晶边界降水量之间的时间滞后对合金蠕变抗性的影响。当NI-2OR-3NB-L3W合金的钨含量增加到17 wt％时，在较低的应力水平下发现了蠕变性能的明显改善，并且与beta阶段之后发生的alpha_2 w-phase的晶粒边界降水密切相关。得出的结论是，诸如beta和alpha_2之类的双阶段引起的晶界降水加强效果是提高蠕变强度的最有效方法之一。为了使NI-CR-NB-W型合金的高温蠕变强度更高，硼龙和锌含量对高 - 纯富特性的影响对高 - 纯化的ni-2ocr ni-2ocr Alloys的蠕变作用。通过硼和锆的添加，抗蠕变性，破裂的破裂寿命较长，而Ni-20cr合金的较大破裂伸长得到了改善。加入硼或锆的破裂寿命和更大的破裂伸长将是由亚晶粒的形成和动态重结晶的形成造成的，这阻碍了晶粒边界的启动和繁殖。核热交换器开发新合金的可能性比几个候选合金（Ni-i-Crys yi-crys and type）更高的核热交换器的可能性。