Radial Forging for Aircraft Landing Gear Components: 300M Steel, Titanium and High-Strength Aerospace Preforms
Aircraft landing gear is one of the clearest examples of why aerospace manufacturers continue to use forged metals even when modern machining centres can create almost any geometry from solid stock. A landing gear system must carry the static weight of an aircraft on the ground, absorb a sharp increase in load during touchdown, tolerate braking and lateral forces during taxiing, and repeat those events over thousands of flight cycles without developing a fatigue crack that compromises structural integrity.
That combination of very high load, cyclic stress and strict weight limits makes the metallurgical history of the component almost as important as its finished dimensions.
For selected cylindrical, stepped and shaft-like landing-gear components, radial forging can provide an efficient route for producing aerospace preforms from 300M steel, titanium alloys and other high-strength materials before heat treatment, NDT and precision machining.
Radial forging should not be presented as the universal manufacturing route for landing gear. Complex beams and irregular structural components frequently require closed-die or other specialised forging routes. The process becomes most attractive when the component geometry is predominantly axial and a radial-forged preform can substantially reduce the amount of material that would otherwise need to be machined away.
Why Landing Gear Is Such a Difficult Structural Application
An aircraft may touch down hundreds or thousands of times during its operating life, and every landing adds another loading cycle to the structure. Even a normal landing creates a combination of vertical impact, bending and local stresses; harder landings magnify those loads, while braking and turning add longitudinal and lateral components.
This is precisely the type of service environment in which fatigue behaviour becomes critical.
A material does not need to reach its ultimate tensile strength on every landing to fail eventually. A relatively small stress repeated a very large number of times can initiate a crack at an inclusion, surface defect, machining mark or geometric stress concentration and progressively propagate it.
For that reason, aerospace landing-gear manufacturing is concerned with far more than simply achieving a high tensile-strength result.
Material cleanliness, forging reduction, grain structure, heat treatment, surface condition, NDT and final machining all contribute to service reliability.
300M: An Ultra-High-Strength Landing-Gear Steel
300M is closely associated with high-load landing-gear structures because it can achieve exceptionally high strength after controlled heat treatment.
It belongs to the same broad metallurgical family as 4340, but its composition and processing are tailored to ultra-high-strength aerospace service. Published aerospace literature commonly places 300M tensile strength around the 1.9 GPa range in landing-gear applications, although the actual acceptance requirement for any component must come from the governing material and engineering specification.
High strength, however, creates a paradox.
The stronger a steel becomes, the more important small defects can become. A tiny inclusion or surface discontinuity that would be tolerable in a low-stress industrial component can have much greater significance in a highly stressed landing-gear part.
That is why aerospace-grade material pedigree and NDT requirements cannot be treated as paperwork added after forging.
Titanium: Lower Density, Different Manufacturing Challenges
Titanium alloys are also used in landing-gear and aerospace structural systems where reducing mass provides sufficient benefit to justify higher material and processing cost.
Ti-6Al-4V is the best-known aerospace titanium alloy, while higher-strength beta and near-beta titanium alloys can be selected for particularly demanding landing-gear applications.
Titanium is significantly less dense than steel, which means designers can potentially achieve high structural efficiency without carrying the same component mass. The trade-off is that titanium demands more careful control during heating, forging and machining.
Its hot-working response changes significantly with temperature, and exposure to oxygen at elevated temperatures can alter the surface layer. The manufacturing process therefore has to be designed around titanium metallurgy rather than adapting a steel forging route.
Where Radial Forging Fits
Radial forging is particularly well aligned with elongated landing-gear preforms because multiple dies act around the circumference while the component is rotated and moved axially.
Historical and academic descriptions of radial forging identify stepped shafts, axles and hollow shafts as core applications of the process. Four-hammer GFM-type machines have long been used for progressively reducing billets while controlling longitudinal profile.
For landing gear, that means radial forging can be considered for long cylindrical or stepped preforms where material needs to be distributed into different axial sections.
It is not a substitute for closed-die forging where the final shape contains major non-axisymmetric features.
Typical Landing-Gear Manufacturing Considerations
| Engineering issue | Why it matters |
| Material cleanliness | Inclusions can become fatigue-crack initiation sites at high stress |
| Grain flow | Forging can create directional material flow aligned with major component geometry |
| Heat treatment | Determines final strength, toughness and hardness |
| Surface integrity | Grinding burns, laps or machining damage can reduce fatigue life |
| UT and surface NDT | Used to identify internal and surface discontinuities |
| Dimensional control | Bearing journals, bores and interfaces require precision machining |
| Traceability | Aerospace programmes may require component history back to raw-material heat |
Aerospace Heat Treatment Is a Controlled System, Not Just a Furnace Cycle
A critical aerospace forging does not become compliant merely because it spent a specified number of hours at a specified furnace set point.
Temperature sensors, furnace uniformity, instrumentation and system accuracy are themselves controlled.
The current revision of AMS2750 is AMS2750H, issued in July 2024, and SAE states that the specification covers temperature sensors, instrumentation, thermal-processing equipment, correction factors, system accuracy tests and temperature uniformity surveys used to ensure metallic materials receive the required heat treatment.
That distinction is important for US aerospace buyers evaluating overseas suppliers.
The question is not simply, “Can you heat treat 300M?”
It is whether the supplier’s thermal-processing system, procedures and approvals satisfy the requirements flowed down by the aerospace programme.
Machining Allowance: Where Radial Forging Can Reduce Cost
Imagine a long landing-gear preform whose largest diameter is required only over one short section.
Machining the entire component from a bar equal to that maximum diameter means purchasing premium aerospace material only to remove much of it as chips.
Radial forging can progressively establish smaller sections before final machining.
This does not eliminate machining because final aerospace tolerances, bearing surfaces and interfaces still require precision operations. Instead, it reduces the amount of unnecessary stock that machining must remove.
With high-value 300M or titanium stock, the economic difference can be substantial.
NDT and Final Verification
Internal and surface inspection perform different jobs.
Ultrasonic testing is used to evaluate internal integrity. Magnetic particle inspection can be applicable to ferromagnetic steels such as 300M, while titanium requires other suitable surface examination methods such as liquid penetrant inspection where specified.
Dimensional verification may then involve CMM inspection, bore measurement and other calibrated metrology.
The important procurement principle is that “100% inspected” has little technical meaning without identifying the inspection method, procedure, coverage and acceptance criteria.
Vinir Engineering and Radial-Forged Aerospace Preforms
Vinir Engineering’s radial forging capability sits within a wider forge-to-finish system covering forging, heat treatment, machining and testing.
For US aerospace buyers, the appropriate starting point is not simply an RFQ containing finished weight.
The technical package should include the final drawing, material specification, applicable aerospace quality clauses, heat-treatment condition, NDT requirements, annual quantities and machining scope so that the manufacturing route can be evaluated properly.
