High Strength Corrosion Resistant Steel for Aircraft Landing Gears and Structures 2021-01-0028
High stressed aircraft landing gear and structural components are subjected to severe loading, corrosion and adverse environmental conditions. Materials such as high strength steels and high-strength titanium alloys are widely used for those critical components. The main criterions for choosing the materials are their strength and fatigue strength, toughness and ductility.
300M steel is widely used for high stress aircraft landing gears and structures; however, this steel is not corrosion-resistant and requires protective coatings.
Cobalt-free, quenched and tempered high strength corrosion resistant steel alloy (“HSCR steel”) provides the same strength, ductility, and toughness as the 300M steel and while it possesses corrosion resistance in salt spray test. HSCR steel has showed no rust after the standard salt spray test in accordance with ASTM B117 using a 5% NaCl concentration, natural pH, at 95°F, for 200 hours test duration.
Aircraft applications of the wrought HSCR steel include landing gear components, rotatable shafts, actuators, flap tracks, slat tracks, fasteners, and others.
Besides forging, the aircraft components can be manufactured from HSCR steel powders by:
Powder metallurgical-based hot isostatic pressing (PM HIP) to the near net shapes
(NNS) followed by finish machining/surface finishing and heat treatment
Additive manufacturing (AM) followed by surface finishing and heat treatment.
Modification of the HSCR steel is applicable for vacuum and investment casting of aircraft hydraulic fluid system, motion control and actuation system, cargo system, and flight safety components.
HSCR steel is a low cost alternative of Ti-6Al-4V alloy. The components made from Ti- 6Al-4V alloy can be substituted by the same weight components made from HSCR steel due to HSCR steel possesses slightly higher specific stiffness and specific strength (ratio of modulus elasticity and ultimate tensile strength to density) and slightly lower ductility and toughness compared to Ti-6Al-4V alloy.