How do CMM and SEM verify deep hole drilling effectiveness in superalloy parts?

Geometric Verification Using CMM

Coordinate Measuring Machines (CMM) are crucial for confirming the dimensional accuracy and alignment of deep-drilled channels in superalloy parts. After machining—often following superalloy CNC machining—CMM inspections verify bore straightness, diameter tolerance and positional accuracy relative to critical features. This is essential for turbine blades or rotors produced via vacuum investment casting, where precise cooling channel orientation ensures optimal thermal flow and structural reliability.

Through 3D scanning and probing, CMM confirms whether the drilling process stayed within engineering specifications and detects any tool deflection, eccentricity or geometric distortion that may affect performance.

Microstructural Evaluation Using SEM

Scanning Electron Microscopy (SEM) provides high-resolution imaging to assess surface integrity inside deep-drilled bores. It is particularly valuable for single crystal castings and equiaxed crystal castings, where SEM can reveal grain boundary deformation, machining-induced micro-cracks or white-layer formation caused by excessive heat. SEM analysis helps confirm that drilling parameters were appropriate and that post-processing such as heat treatment or HIP successfully restored microstructural stability.

Combined with material testing and analysis, SEM is used to detect machining damage that may not be visible through conventional inspection methods.

Integration for Structural Validation

Using CMM and SEM together allows both dimensional accuracy and microstructural integrity to be assessed. CMM ensures cooling channels or lubrication bores meet design geometry, while SEM confirms that surface and grain structure remain intact. This dual validation is especially important in aerospace and power generation applications, where failure due to drilling damage would compromise safety and engine efficiency.

By combining dimensional verification with microstructural diagnostics, CMM and SEM provide a comprehensive evaluation framework to ensure deep hole drilling delivers effective cooling, stable structure and long-term reliability.