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Titanium Aerospace Parts and the Requirements That Come With Them

Aerospace titanium work is not harder to cut than any other titanium. It is harder to buy, because the requirements around the part are heavier than the part itself.

Get those requirements onto the RFQ and your three quotes become comparable. Leave them off and every shop assumes something different.

Why titanium is in the airframe at all

Three reasons, in order of how often they decide.

Strength to weight at temperature. Ti-6Al-4V keeps working to roughly 400 C, where aluminium alloys have long since given up. Engine pylon fittings, firewall hardware and bleed air components live in that band.

Galvanic compatibility with carbon fibre. Aluminium in contact with CFRP corrodes. Titanium sits close enough to carbon on the galvanic series to be safe, which is why the shift to composite airframes pulled titanium content up with it.

Strength in a small envelope. Where there is no room to grow an aluminium section, titanium is the way out.

Typical parts: brackets and fittings, lugs and clevises, hydraulic manifolds, engine mounts, seat track hardware, fastener components, actuator bodies.

The material specification matters more than usual

This is the most common avoidable problem in an aerospace titanium RFQ.

Callout	What it is	Consequence
Grade 5	Generic	Shop buys to ASTM B348
ASTM B348	General industrial bar standard	Fine for industrial, may not satisfy an aerospace drawing
AMS 4928	Aerospace specification for Ti-6Al-4V bar	Tighter requirements, different stock pool
AMS 4911	Ti-6Al-4V sheet, strip and plate	Different product form
AMS 4967	Ti-6Al-4V bar, solution treated and aged	Heat treated condition specified

If your drawing calls AMS 4928 and your RFQ says only “Grade 5 titanium”, the shop will quote against material it can get, which may not be AMS material. The parts arrive with the wrong certificate and the problem is discovered at receiving inspection.

Put the full specification on the RFQ, including the condition: annealed, or solution treated and aged.

Traceability, in aerospace terms

Every part has to be traceable to a heat, and the chain cannot break.

• The mill certificate is to EN 10204 3.1, tied to a heat number.
• The shop records the heat against the order and segregates the material.
• Heat numbers are transfer marked onto each blank before the original marking is machined away, witnessed by QC.
• Identification survives every outside process.
• The certificate of conformity names the part, the quantity and the heat.

Ask a prospective shop how step three works in practice. The answer separates the shops that have done aerospace work from those that have read about it.

First article inspection

AS9102 is the standard format for a first article inspection report. Every characteristic on the drawing gets a number, or “ballooned”, and every one is measured and recorded on standard forms, along with material and special process certifications.

It is thorough, and it is expensive in inspection hours. A part with 120 characteristics is a real piece of work to report on.

Decide and state:

• Do you need an AS9102 report at all?
• On the first release only, or on every release?
• Full FAI or partial, if only some features changed?
• Who reviews and approves it, and how long does that take?

That last question belongs in your own schedule as much as the shop’s.

Special processes and NADCAP

Heat treatment, non destructive testing, chemical processing and coating are special processes in aerospace terms, which means the result cannot be fully verified by inspecting the finished part. NADCAP accreditation covers the suppliers who perform them.

For a machined titanium part the special processes that come up are usually:

• Stress relief or solution treatment and ageing.
• Penetrant inspection on critical parts.
• Chemical processing, including pickling and passivation.
• Anodizing to AMS 2488.

Most machine shops subcontract these to accredited houses. That is normal. What matters is that your shop knows which of its subcontractors hold which approvals, and can name them.

Export control, said plainly

Some aerospace and defence parts are subject to export control regimes in their country of origin. If your part is controlled, that constrains who may see the drawing, let alone quote it. Say so at the start of the conversation rather than after a drawing has been circulated. We do not accept RFQs for controlled defence articles.

The RFQ checklist

Material: Ti-6Al-4V per AMS 4928, annealed. Certificate: EN 10204 3.1, heat number on the certificate of conformity. Quality system: AS9100 required / ISO 9001 acceptable. First article: AS9102 report on the first release only. Special processes: stress relief between rough and finish. Anodize per AMS 2488 Type II. Tolerance: ISO 2768-m general, three features called out on the drawing. Quantity: 12 now, expected 60 per year. Needed by: date.

Eight lines. Every shop that receives it is quoting the same part, which is the entire point.

Frequently asked questions

Keep reading

• Titanium for Medical Devices: What Changes Compared With Industrial Work
• Drilling Titanium: Speeds, Heat and Why Holes Fail First