<p>The aircraft engine casing, a pivotal component, is prone to early cracking during service, severely compromising the safety and lifespan of aerial vehicles. This study delved into the cracking mechanism at the lap component of aeroengine inner casing during service by examining the microstructural characteristics of specimens before and after service, alongside an analysis of microstructural evolution and mechanical properties under simulated service conditions. Experimental findings indicated that, post-service, a small number of locations in the specimens exhibited the adhesion of Mo-rich phases with Mo and Ti compound phases, accompanied by a notable increase in grain size compared to the original specimens. Under simulated high-temperature environments and thermomechanical loading conditions, Mo-rich phases precipitated after reaching 800&#xa0;°C. Additionally, cracks emerged in the specimens under thermomechanical loading, leading to a transition in fracture behavior from ductile to brittle. In summary, the primary causes of cracking in aircraft engine casing materials were as follows: the aggregation of Mo and Ti compound phases and Mo-rich phases at grain boundaries, significant grain size enlargement, and a shift in the fracture nature of the alloy material. This study offers foundational research insights for the design and preparation of alloy materials for aircraft engine inner casings.</p>