CoatingIQ
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Wrap-up

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Lesson 12·Failure analysis

Common build failures: what actually goes wrong on the shop floor

The recurring build screwups that scrap forge dies in the first 50K cycles, grouped by where in the build chain they originate, and the inspection step that catches each one before it ships.

7 min readLesson 12 of 13

Tying it together

What this means on the shop floor

Heat-treat acceptance includes hardness on the witness coupon, the full cycle trace, the temper count, and a retained austenite measurement. The hardness number alone is insufficient.

EDM acceptance includes Ra on the cavity surface, a cross-section on a witness coupon showing recast under the spec, and the recast removal step documented in the routing.

Machining acceptance includes silicone replica or optical CMM on every critical radius before each downstream step. The as-built radius is the controlled feature, not the print radius.

Incoming material acceptance includes spark test or XRF chemistry on every block, with heat-number traceability against the mill cert for premium grades.

Each of these inspections has a witness artifact: a coupon, a cross-section, a CMM report, an XRF reading. The certificate without the artifact is testimony, not evidence.

Common confusions

A heat-treat certificate that lists hardness and temper temperature is not proof of correct heat treatment. It is proof of the values that were recorded. The cycle trace, the witness coupon hardness, and the retained austenite measurement are the evidence. Anything else is testimony.

EDM finish settings labeled "fine" or "skim" do not mean recast-free. They mean lower-energy recast. Verify with a cross-section on a witness coupon, not with a vendor's verbal claim.

Stress relief between rough and finish is not optional on through-hard work. It is the difference between predictable distortion and a die that warps to a shape no one designed.

Retained austenite is not visible on a hardness tester. A part can read 50 HRC and contain 15 percent retained austenite. The hardness number does not catch it. The diffraction or saturation measurement does.

Material verification is not a quality theater step. Grade substitution at the distributor level happens and takes out production die programs. A 30-second spark test or a 60-second XRF read is cheaper than the postmortem.

Up next: where the engineering decisions live.

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