In aerospace and defense manufacturing, time is everything. A failed hydrogen embrittlement test can bring production to a halt, jeopardize delivery timelines, and trigger costly retesting. That’s where Step Load Testing comes in.
At Omega Research Inc., we’re one of the few labs in the world informing our customers of ASTM F519-compliant Step Load Testing, a 6-hour solution that can turn a failed test into a passing one without sending in new samples or starting from scratch.
How Step Load Testing Works
Step Load Testing is a follow-up procedure specifically designed for situations where one specimen fails during the standard 200-hour sustained load test. Instead of discarding the entire test set, SLT uses the remaining three samples to provide definitive results.
The process incrementally increases the load by 5% of the Notch Fracture Strength (NFS) every 2 hours, building up to 90% NFS over the 6-hour testing period. This systematic approach evaluates the material’s resistance to hydrogen-induced cracking while delivering same-day results.
Why SLT Matters to Your Operation
In industries where every hour of downtime has a dollar value attached, SLT provides a critical safeguard against unexpected test failures. Delays caused by reprocessing samples, re-plating, and waiting on retests can derail even the best-managed production timelines.
By opting for automatic SLT on your purchase order (when allowed by spec), you can avoid many of those pitfalls. The test uses existing samples, requires no special preparation, and can be completed the same day a single sample failure is completed. That means fewer disruptions and faster decision-making for your production team.
And the savings aren’t just hypothetical. Replacing a full four-sample test—along with all the materials and labor involved—can easily cost thousands. With SLT, that cost is drastically reduced.
How SLT Fits into the Testing Lifecycle
Understanding how SLT works within the ASTM F519 framework helps you make smarter decisions:
ASTM F519 Section 11 – Interpreting Results
- No Fractures: Process is considered non-embrittling. Test passes.
- One Fracture: SLT may be performed on the remaining three samples. If all three remaining samples pass SLT, the process is considered non-embrittling.
- Two or More Fractures: Process is embrittling. Retesting or process revisions required.
- Anomalous Failures: If sample prep, bake, or other process errors are suspected, retesting with new samples may be allowed. However, any failure in retesting = embrittling.
Proven Results from Omega’s SLT Program
Omega Research has conducted more SLT tests than nearly any lab in the world. And the results speak for themselves:
- 497 sets with a single failure in a 200-hour test
- 365 sets eligible for SLT (74% opportunity rate)
- 234 sets passed SLT successfully (64% success rate)
That’s 234 plating/coating runs that didn’t need to be repeated, saving our customers thousands of dollars and weeks of lost time. If your plating or coating spec allows for Step Load Testing, schedule it in advance, even if your 200-hour test might pass. Just add automatic step load to your purchase order and save days or even weeks of delays if a single specimen fractures.
