Premature Failure of a Nickel Aluminum Bronze Vacuum Pump

Nickel Aluminum Bronze (NAB) is frequently the material of choice for the fabrication of equipment such as pumps, valves, etc. for seawater service.  In general, the corrosion performance of this alloy material in seawater is very satisfactory.  However, component failures have been occasionally encountered.  The present paper discusses the premature failure of a NAB vacuum pump at the seawater treatment plant of the Kuwait Oil Company (KOC).  The failure investigation consisting of metallographic examination of the alloy microstructure, hardness profiles, and SEM microprobe analysis indicated that the cause of failure was attributable to the use of a non-specific grade of NAB in an improperly heat treated condition  The corrosion morphology indicated cavitation, erosion-corrosion, and selective leaching to have contributed to the failure.
Keywords:     Nickel Aluminum Bronze (NAB), Failure Analysis, Seawater Service,