Microstructural and oxidation effects on fatigue crack initiation mechanisms in a turbine disc alloy
Microstructural and oxidation effects on fatigue crack initiation mechanisms in a turbine disc alloy
复制标题
DOI：
10.1007/s10853-022-08120-9
复制
发表时间：
2023-01
影响因子：
4.5
通讯作者：
D. Kim;R. Jiang;P. Reed
中科院分区：
文献类型：
--
作者：
D. Kim;R. Jiang;P. Reed
研究了不同γ′分布和晶界碳化物分布的RR 1000涡轮机盘合金的显微组织和氧化对疲劳裂纹萌生和早期扩展过程的影响。疲劳测试在650 °C空气中在三点弯曲和梯形波形载荷（具有90 s停留）下进行。两种γ′变体的失效模式都明显具有晶间特征。许多疲劳裂纹被认为是在晶界处开始的，在碳化物和晶界之间的表面和/或界面处具有凸出的富钴氧化物，这是由施加的载荷辅助的氧化损伤引起的。寿命缩短与显著的晶间裂纹萌生和频繁的随后裂纹聚结事件密切相关，这导致疲劳裂纹扩展（FCG）速率提高。当晶界处存在更多连续碳化物时，晶界特征和增强的FCG的程度更显著。
Effects of microstructure and oxidation on fatigue crack initiation and early propagation processes were investigated in RR1000 turbine disc alloy with different γ′ distributions and carbide distributions on the grain boundary. Fatigue tests were carried out under three-point bending and trapezoidal waveform loading (with a 90 s dwell) at 650 °C in air. The failure mode in both γ′ variants is clearly characterised by intergranular features. A number of fatigue cracks are seen to initiate at grain boundaries with bulged Co-rich oxides at the surface and/or interfaces between carbides and grain boundaries, resulting from oxidation damage assisted by applied loading. Reduced lifetime is closely linked to significant intergranular crack initiation and frequent consequent crack coalescence events, which results in enhanced fatigue crack growth (FCG) rates. The extent of intergranular features and enhanced FCG are more marked where more continuous carbides exist at the grain boundary.