The article reviews National Transportation Safety Board (NTSB) investigations into multiple Cessna 210 aircraft accidents caused by failed hydraulic actuators in the main landing gear systems. Investigators discovered a pattern of fatigue cracks in 7075-T6 aluminum actuator barrels that initiated at corrosion pits along the retaining ring groove, propagated under cyclic loading, and eventually resulted in circumferential and longitudinal fractures that leaked hydraulic fluid. Although these failures have not yet caused significant injuries, they present serious safety risks by impairing pilots' ability to fully extend and lock the landing gear. The article details the metallurgical examinations that revealed multiple crack initiation sites containing chlorine-rich aluminum oxide pits, some with cadmium remnants from the adjacent steel retainer ring, suggesting potential corrosion mechanisms. The researchers conclude that the combination of thin-walled design, stress concentrations at the retaining ring groove, susceptibility of the high-strength aluminum alloy to corrosion, and possibly inadequate inspection procedures all contributed to these premature failures, prompting ongoing work with the FAA to address the issue.

AM&P spoke with Brian Donahue of Canvus to learn how this manufacturer upcycles end-of-life wind turbine blades into furniture for communities, parks, and schools.

Nanobrazing is an innovative brazing technique that uses nanomaterials as the filler materials. Incorporating nanobrazing into conventional technologies such as vacuum and laser brazing creates a new frontier for repairing turbine blades and vanes. Due to the unique “nanopowdering” of filler materials, the metallurgical mechanisms and thermodynamics of nanobrazing show promise for innovative applications.

Modern, high quality induction heat treating equipment must be readily available and flexible enough to allow for easy retooling and reprogramming to process a variety of parts. This article focuses on the technical revolution taking place in induction heating, which for the first time enables preprogramming of induction equipment to change frequency and power during the heating cycle in the same manner manner as machinists have been programming CNC machines for years. This is illustrated through a case study of induction hardening a shaft-like component.

The invention of the single crystal jet engine blade under Frank Versnyder and a team of scientists at the Pratt & Whitney Division of United Technologies is considered one of the 50 greatest advances in metallurgical history.

Oxide dispersion strengthened (ODS) alloys have potential to improve turbine blade temperature capability beyond that of superalloy single crystals. In this article, the case is made for the potential to replace single crystals as high-pressure turbine blades with ODS nickel-base alloys. ODS alloys combine proven technology, substantial gains in capability over today’s single crystal alloys, and a clear development path to overcome identified risks.

During the past 30 years, enormous research has been devoted to developing titanium-base intermetallics for use in gas turbine engines as lightweight alternative to nickel-base superalloys. This article presents a brief history of Ti 2 AlNb and efforts to mature this material for commercial component production. The article includes processing experience insights gained from a current R&D program in China.

Researchers are supplying the aerospace industry with innovative technologies to support the next generation of more efficient and reliable aircraft. This article describes a novel laser technology for measuring stress and damage in the protective ceramic coatings applied to turbine engine blades to prolong their life.

An industry pioneer shares a historical overview of the early days of single crystal superalloy development.

A microscale fatigue testing technique for characterizing mechanical response and relating it to microstructure promises to improve fatigue life prediction for turbine engine components.

High-speed rotating components in gas turbines, flywheels, and turbo machinery can be a lethal threat in the event of a failure due to the energy they possess. To assess the risks associated with such failures, rotor assemblies can be evaluated by spin testing although there are inherent risks in the tests themselves. This article discusses these risks and explains what can be done to minimize the potential dangers of high-speed performance testing.

This case study describes how electron-beam melting, a powder bed additive manufacturing technology, helped reduce the cost and material scrap associated with the production of Ti-6Al-4V brackets used in the hot side of the engine on Lockheed Martin's Joint Strike Fighter.

Neutron-based imaging and measurement techniques are an ideal complement to x-ray methods for characterizing additively manufactured materials and components. This article presents examples showing how neutron radiography and residual strain measurements reveal the internal structure and stress distributions in highly engineered turbine blades produced by additive processes. It also discusses the development of neutron characterization tools at ORNL and a recent effort in which they were used to evaluate stress-relief treatments for large-scale metal AM structures.

Clearance-control coatings play a major role in gas turbine engines by minimizing the air gap between rotating blade tips and engine casings. An improvement of just 125 µm can reduce fuel consumption by 0.5%. This article discusses the potential impact of new materials being considered for blade tip coating systems, including NiCoCrAlY bond coats and matrix layers with Hf, Re, or Si additions for better oxidation and creep resistance, embedded angular CBN particles for enhanced incursion of abradable shroud coatings, and double or Pt aluminide topcoats for extended oxidation protection.