Search Results

The latch body is a safety critical 4340 steel part that is currently used in the cargo hook of a CH-47 military helicopter. Approximately 5×2×2 inches in dimension, this safety critical part is nestled within the cargo hook assembly and facilitates the operation of the load beam (hook) during its payload cycles. This paper mainly focuses on the methodology and design advantages of converting a wrought two piece latch-body into a single piece machined component. The application of austempering heat treatment to improve mechanical properties and eliminate surface cracking vis-à-vis generic oil quenching and tempering treatment is discussed. The application of laser technology for surface hardening of the austempered latch body is reported. Mechanical testing of austempered 4340 steel, microstructural examination, characterization of the laser and induction hardened layers, and preliminary testing to evaluate the integrity of the hardened layers is presented.

Heat treated 7000-series aluminum alloys exhibit the highest strength and toughness amongst wrought aluminum alloys, and are used for a variety of applications in the defense and the aerospace industry. The corrosion resistance of these alloys is strongly dependent on final thermo-mechanical and tempering treatment. Many surface modification techniques are used to protect these alloys against general, exfoliation and pitting corrosion. Hard anodizing is a surface modification technique that imparts corrosion and wear resistance to 7000-series aluminum alloy parts. However, if the anodized parts experience cyclic loading conditions, there is a risk that the brittle anodized layer may undergo cracking thereby compromising the corrosion resistance of the 7000-series aluminum components in service.