High Strength Corrosion Resistant Steel for Aircraft Landing Gears and Structures

Abstract

<div class="section abstract"><div class="htmlview paragraph">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.</div><div class="htmlview paragraph">300M steel is widely used for high stress aircraft landing gears and structures; however, this steel is not corrosion-resistant and requires protective coatings.</div><div class="htmlview paragraph">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.</div><div class="htmlview paragraph">Aircraft applications of the wrought HSCR steel include landing gear components, rotatable shafts, actuators, flap tracks, slat tracks, fasteners, and others.</div><div class="htmlview paragraph">Besides forging, the aircraft components can be manufactured from HSCR steel powders by:<ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Powder metallurgical-based hot isostatic pressing (PM HIP) to the near net shapes</div></li></ul></div><div class="htmlview paragraph">(NNS) followed by finish machining/surface finishing and heat treatment<ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Additive manufacturing (AM) followed by surface finishing and heat treatment.</div></li></ul></div><div class="htmlview paragraph">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.</div><div class="htmlview paragraph">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.</div><div class="htmlview paragraph">Industrial production of HSCR steel is underway.</div></div>