Tools failures can add handsomely to drilling, completion and recovery costs. Reconstructing the failure sequence may uncover material issues or reveal assembly errors.
Laboratory examination under the stereomicroscope revealed extensive cracking in the outermost layers of the surface. Failure began in the ultra-hard surface. A metallurgical specimen taken through the cracked zone revealed incorrect heat treatment as the culprit.
Evaluation of the fractured mandrel revealed the correct material, machining and heat treatment. Failure was attributed to unforeseen impact overloading.