Development of Custom® 465 Corrosion Resisting Steel for Landing Gear Applications

Existing high-strength, low-alloy steels have been in place on landing gear for many years owing to their superior strength and weight performance. However, there have been major advances in improving the strength of high performance corrosion resisting (CRES) steels. These materials have superior environmental robustness and partially remove the need for harmful protective coatings such as chromates and cadmium now being considered for removal under REACh legislation (local special treatments are still required to protect against galvanic corrosion). Use of CRES steels also offers reduced in-service maintenance costs and is an economically favourable alternative to high performance titanium alloys.

A Technology Strategy Board funded collaborative project is underway targeting a refined specification Carpenter Technology Corporation Custom^®465 precipitate hardened stainless steel (C465) to replace the current material on an Airbus A320-Family main landing gear, main fitting component developed by Messier-Bugatti-Dowty. This work is a collaborative project between Airbus, Messier-Bugatti-Dowty and Carpenter Technology Corporation.

So far nine main fittings have been successfully forged from C465 billets and the manufacturing process has been developed to fully understand industrial production of these components. It is intended to develop and test a fully CRES landing gear in the near future.

As part of this project, an extensive series of coupon tests on four production heats of C465 with the refined specification were conducted, to obtain a full range of machining, mechanical, fatigue and corrosion properties. Each production heat was drawn-down to give a range of reduction ratios found on the forged component.

This paper presents a statistical analysis of the C465 material properties data including calculation of static material allowables, mean and lower tolerance fatigue curves. Cutting parameters and cutting tools tailored to machine C465, for the range of techniques used in the manufacture of an A320-Family main fitting, are also presented.