Application of Direct Metal Deposition Process for Failure Prevention of Oil Pump Gear Shaft in an Aero Engine
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TECHNICAL ARTICLE—PEER-REVIEWED
Application of Direct Metal Deposition Process for Failure Prevention of Oil Pump Gear Shaft in an Aero Engine Srinivasakiran Tumuluri . P. Murugeshan . R. K. Mishra . V. V. Subrahmanyam
Submitted: 13 April 2017 ASM International 2017
Abstract Direct metal deposition process has been adopted for repair of oil pump gear shaft of an aero engine. The process is first optimized for the specific application of oil pump gear shaft material on a specimen and then the actual part was applied with deposition. The deposition on the gear shaft is validated through stringent quality checks and functionality check of the oil pump during bench test and engine test. The successful adoption of the deposition process is able to prevent failures which would otherwise cause catastrophic failure of the aero engine. Oil pumps are now withdrawn from service at a predetermined time prior to its scheduled inspection and overhaul for application of metal deposition. Keywords Wear
Defect analysis Wear resistance
Introduction Oil pump is an important line replaceable unit (LRU) of an aero gas turbine engine. It works under pressure and supplies oil to various parts that need lubrication. Irrespective of the design philosophy, it circulates oil through heat
S. Tumuluri P. Murugeshan Engine Division, Hindustan Aeronautics Limited, Bangalore, India R. K. Mishra (&) Regional Center for Military Airworthiness, Bangalore, India e-mail: [email protected] V. V. Subrahmanyam Center for Nano and Material Sciences, Jain University, Bangalore, India
exchangers and scavenge pumps and returns the oil to the oil tank. The elements of the oil pump largely depend on the type of the engine it is intended for and the heat load to be transported. The two most common type of oil pumps are the gear and gerotor, with the gear type being the most commonly used in aero engines. Any malfunction of the oil pump or failure of the drive will have a detrimental effect on the rotating parts of the engine. Cases of gear failure have seen to rise the bearing temperatures or seizure of rotor shafts in aero engines [1–4]. The oil pump in the present study is a gear type and is mounted on the engine deriving the drive from the gear train of the engine accessory gearbox. This pump gear is supported by plain bearings. Cases of high oil temperature warning or bearing/shaft seizure have led to premature withdrawal of engines or accessories [4, 5]. During investigation, it is observed that the bearing diameter get worn out due to service wear. Wear of gear wheel shaft has also been noticed during repair and overhaul (ROH) which cannot be restored by chrome plating due to thickness constraint, as chrome plating is not be effective beyond 76 lm. thickness. To overcome this limitation of hard chrome plating, a new cutting edge process ‘‘direct metal deposition (DMD)’’ has been adopted in the present case to regain the gear shaft dimension. DMD is a process of building metal layer by layer by high intensity laser beam with controlled
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