Ni-20Cr-18W基高温合金热轧组织演变和力学性能

Microstructure Evolution and Mechanical Properties of As-rolled Ni-20Cr-18W Base Superalloy

摘要:

采用力学试验机、扫描电子显微镜（SEM）研究了热轧态固溶强化型Ni-20Cr-18W基变形高温合金的室温拉伸行为、微观组织演变及断口形貌，结合X射线衍射（XRD）确定了合金的相结构。结果表明，合金热轧态组织由再结晶后的细小等轴晶粒构成，晶粒尺寸为20~30 μm，可达ASTM 7级，组织中可见大量退火孪晶，M6C型碳化物颗粒主要弥散分布在晶界上。热轧态合金由于组织细化使抗拉强度升高，断裂方式以穿晶断裂为主，碳化物颗粒成为导致拉伸断裂的裂纹源，使合金塑性下降。合金的室温拉伸断口呈韧性等轴韧窝，韧窝中心为M6C型碳化物颗粒。

Abstract:

Microstructure and mechanical properties of solution strengthened Ni-20Cr-18W rolled superalloy were investigated. Microstructure features and phase composition investigations indicate the average equiaxed grain size of the as-rolled alloy is 20~30 μm (ASTM 7). Significant annealing twins can be observed within the microstructure and most M6C-type carbides mainly disperse on the grain boundary. As-rolled Ni-20Cr-18W superalloy maintains a high tensile strength due to the small grain size. Low ductility of the as-rolled superalloy can be ascribed to M6C-type carbides, which act as crack source on the grain boundary, and the transgranular fracture features with typical dimple-ductile characteristics are observed.