A Lab Has the Certificates. Can You Accept the Test Report?

Three certificates, three different jobs

Start with ISO/IEC 17025 capability. It asks whether the lab can run the tests properly: people, equipment calibration, methods, records and reporting. Nadcap accreditation for materials testing laboratories builds on ISO/IEC 17025 and adds test-specific requirements for each test category. The most visible one is proficiency testing: the lab regularly tests the same samples as its peers and compares results. Customer requirements sit on top. When they are in writing, they take precedence over the Nadcap criteria.

The AS9100 certificate is a separate thing. It covers the management system only, and conformity to 9100 does not by itself show that a lab can do the testing. The certificate on the wall tells you the lab runs documentation, audits and corrective action. It's best not to use it as evidence of testing capability. The two are easy to mix up.

Figure: Three layers of assurance for an external testing laboratory, and where AS9100 sits

Read the scope first

Nadcap accreditation is granted by test category. Chemical analysis, tensile, metallography and hardness each have their own test codes. A lab accredited for hardness isn't automatically accredited for fatigue. When a report comes in, open the certificate scope first and look for the test you ordered.

Take chemical analysis. Alloying elements such as titanium, aluminum, nickel and chromium are usually measured by spark optical emission (OES) or inductively coupled plasma (ICP). Carbon, sulfur, oxygen, nitrogen and hydrogen are measured by combustion or fusion methods, on different equipment. Nadcap AC7101/14 Rev. NA (2023-09-06 edition) lists the two groups separately, so a chemistry lab may have the spectrometry codes without the combustion or fusion ones. If your order calls for oxygen, nitrogen or hydrogen, confirm that item is in scope.

Tensile testing works the same way. Room temperature and elevated temperature are separate items, and creep and stress rupture are separate again.

Proficiency testing: customers differ

Nadcap requires proficiency testing, and how often depends on the test category: every 2 years for chemical analysis, tensile and hardness, every 5 years for fatigue and fracture toughness. For compression, impact and bend testing, AC7101/14 requires neither proficiency testing nor an internal round robin, so there is no such record to look at. You will need other evidence. Also, a PT record only shows that the lab has compared itself with its peers. It doesn't guarantee every test was sound. Treat it as supporting information, not a conclusion.

The provider matters too. AC7101/14 splits customers into two approaches. Some aerospace customers ask for a PRI-recognized provider and allow a step down only when none is available. Other customers, if they name none, accept a provider approved by the Nadcap Materials Testing Laboratories Task Group (MTLTG), or an ISO 17043-accredited provider. The same PT record may be enough for one and not for the other. Which one applies to you? Asking your customer is the surest way to find out.

Where the customer or purchase order says something specific, follow that, and treat the certificate as supporting evidence.

Questions worth asking before acceptance

How to decide once you have the answers

Once you have the answers, should you accept? Here is one way to decide:

• Scope does not match. Hold acceptance for now. If the test isn't in the scope, no number of other certificates can show the lab is capable of that test.
• Scope matches, customer requirements not yet confirmed. Ask first. Confirm the proficiency test provider and what the report must contain, then release.
• Scope, customer requirements and records all line up. You can consider accepting. The inspection and record requirements in the purchase order continue as usual, including any sampling checks.