# How a Turbocharger Manufacturer Cut Bolt Costs 40% by Switching from Inconel 718 to A-286

> A Tier-1 turbocharger supplier was specifying Inconel 718 for all hot-side bolts, until our engineering team showed them they only needed it on 3 of 12 positions.


When a German Tier-1 turbocharger supplier sent us their RFQ last March, all 12 hot-side bolting positions specified Inconel 718. The bill of materials came to €47,000 per production batch. Our application engineer asked one question: "What's the measured flange temperature at each position?"

The answer changed everything.

## The data they hadn't looked at

The customer had thermocouple data from 18 months of engine dyno testing. Positions 1-3 (turbine inlet flange) consistently measured 660-690°C. Positions 4-9 (bearing housing and compressor backplate) measured 420-550°C. Positions 10-12 (compressor outlet) never exceeded 380°C.

Only three positions, the turbine inlet flange studs, operated above A-286's 650°C limit. The other nine positions were being over-specified by 100-300°C of temperature margin, at 2-3x the material cost.

## The fix: a split bill of materials

We proposed:
- Positions 1-3: Inconel 718 studs (AMS 5662), as originally specified
- Positions 4-9: A-286 studs (AMS 5732), 650°C rated, 60% lower material cost
- Positions 10-12: A-286 hex bolts (ASTM A453 Grade 660 Class D), 380°C max, standard cost

Total BOM: €28,000, a 40% reduction. Same performance. Same certification level (EN 10204 3.1 across all positions). Same lead time.

## The catch: don't blindly copy the split

The split works because this customer's temperature distribution is uneven. A different turbocharger with a different turbine housing design might have different hot spots. The principle (measure before you specify) applies universally. The specific split does not.

We've since applied the same methodology to three other turbocharger programs. The savings range from 25% to 55%, depending on how conservatively the original specification was written. The common thread: nobody had cross-referenced the bolt specification against actual measured service temperatures before.