该文以采用9%Cr含B铁素体耐热钢为母材、2.25%Cr为填充金属的接头为对象, 研究了高温时效过程对接头中的碳迁移层及其附近区域的影响。研究发现: 经高温时效后, 接头富碳区中的析出物发生粗化且数量增多, 而贫碳区中析出物变化不大, 导致贫/富碳层的硬度差异增大。有限元计算结果表明: 在接头受载情况下, 贫碳区会成为首先破坏的部位, 并且高温时效会加剧这种破坏。透射电镜(TEM)结果表明: 9%Cr含B钢热影响区(HAZ)中的晶界析出物在时效后粗化不明显, 而晶内析出物则发生了明显的粗化, 这主要是由于B在晶界聚集并通过占据析出物周围的空位阻碍了析出物粗化。
This study uses 9%Cr parent metal containing boron and 2.25%Cr weld metal to study the influence of long-term aging at elevated temperature on the carbon migration between the parent metal and weld metal. The size and number of precipitates in the carbon-enriched zone increase after long-term aging, but the precipitates in the carbon-denuded zone change little, which increases the differences in the mechanical properties between the carbon-enriched and carbon-denuded zones. Finite element analyses indicate that the carbon-denuded zone is damaged first by bearing loads with the damage increasing with long-term aging. Transmission electron microscope (TEM) pictures show that the precipitates at the grain boundaries of the heat affected zone in the 9%Cr parent metal change little, but precipitates inside the grains become coarse after long-term aging. Boron is responsible for the changes of the precipitates at grain boundaries and inside the grains, because the boron tends to segregate at the grain boundaries, which slows coarsening of the precipitates by occupying vacancies around the precipitates.
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