Oxide Reduction Strategies in Low Alloy Steels for PM-HIP
Business challenge
Product Innovation
Process Innovation
Sector
Technology or capability
Materials Engineering
The Challenge
Main landing gear components (e.g. main fittings, sliding pistons) are critical for aircraft safety, competitiveness, influencing cost, development time, and environmental footprint. Current manufacturing depends on large forgings, with no UK production footprint.
The Landing-Gear Industrial Breakthroughs (I-Break) programme, a 5-year IUK/ATI-funded initiative, aims to transform component manufacturing using innovative techniques such as powder metallurgy hot isostatic pressing (PM HIP), direct energy deposition (DED), electron beam (EB) welding and rotary friction welding (RFW). Among these technologies, MTC, as a partner in the I-BREAK programme, will develop and validate PM-HIP, a powder-based solid-state manufacturing process capable of producing high-performance components with isotropic properties.
Early PM HIP trials have indicated that while tensile strength met specification, ductility and toughness were below target, one of the reasons was attributed to oxides at prior particle boundaries (PPBs), a key challenge in PM-HIP processing predominantly for steels and Ni-based superalloys.
MTC's Solution
One way to reduce surface oxides is through chemical reduction of the already produced powder. This process introduces a reactive gas, most commonly hydrogen, which bonds with the oxygen in the oxide to form water vapour. This reaction not only removes oxides at lower temperatures, but also maintains a reducing environment, preventing the metal from re-oxidising.
MTC trialled two techniques:
- Hydrogen purging during hot degassing
- Processing the powder through a fluidised bed reactor (FBR), in collaboration with Phoenix Scientific Industries Ltd (PSI).
Two powders of varying starting oxygen parts per million (ppm) were used in the trials.
Reconditioning metal powder restores consistency, enhances performance, and transforms valuable material into a reliable feedstock for the most demanding engineering applications.
Charley Carpenter, Chief Engineer, Materials Technology
The Outcome
Both techniques reduced the ppm of 300M steel powder. Hydrogen purging was most effective for powder with high initial PPM, while the FBR proved effective across all starting levels.
Benefits to the Client
Both techniques improved the ductility after HIPing, enabling PM HIP of 300M to meet the required tensile properties.
When the starting powder falls below specification, these technologies offer a transformative pathway for powder recovery and reconditioning, leading to:
- Recovery of Out-of-Spec Material: Reuse degraded or aged powder, reducing waste and improving resource efficiency.
- Operational and Strategic Gains: Lower material costs, shorten lead times, strengthen supply chain resilience for powder feedstocks containing critical minerals, and future-proof operations against sustainability and regulatory demands.
