Incident Description
During the initial portion of the takeoff roll, before the engines attained takeoff power, the No. 2 engine experienced an uncontained failure of its 8th stage high-pressure compressor (HPC) disk. In response, the takeoff was aborted. The aircraft was subsequently towed to the gate, and passengers were bussed to the terminal.
Metallurgical Examination
A detailed metallurgical analysis of the 8th stage HPC disk showed that a significant amount of cadmium was present on the steel base metal in the vicinity of the fracture surfaces. Additionally, the nickel coating on the disk was found to be inadequate. The disk had accrued 359 flight hours since its last overhaul. It had been nickel-cadmium plated in March 1996 and remained in storage until February 1998, when it was installed in the accident engine during a repair.
Findings on Other Disks
Other HPC disks installed in the accident engine, which had been nickel-cadmium plated by the same company as the 8th stage disk, were also discovered to have inadequate nickel coating.
Plating Process
In the nickel-cadmium plating process, the nickel layer acts as a barrier coating between the cadmium and the steel part. This barrier is intended to prevent the cadmium from coming into direct contact with the steel, as such contact can cause cadmium embrittlement.