Overlap
Overlap is the protrusion of weld metal beyond the weld toe without fusion to the base metal, producing a notch-like discontinuity that reduces fatigue performance.
Definition
Overlap (sometimes called "cold lap") occurs when weld metal flows onto the base metal without proper fusion, often from low travel speed or contaminated joint surfaces. It is rejectable per AWS D1.1.
Related terms
- Undercut — Undercut is a groove melted into the base metal adjacent to the weld toe that is not filled with weld metal, reducing wall thickness and acting as a stress concentrator.
- Lack of Fusion (LoF) — Lack of fusion is a weld defect in which the deposited weld metal fails to fuse with the base metal or with the previous weld pass, producing a planar discontinuity along the fusion boundary.
- Visual Testing (VT) — Visual Testing (VT) is the most basic NDT method, using direct or remote optical observation — sometimes aided by mirrors, borescopes, or cameras — to identify surface defects, geometric anomalies, and condition of components.
More defect terms
Crack · Lack of Penetration · Slag Inclusion · Porosity · Burn-Through · Weld Spatter · Lamination · Lamellar Tearing · Hydrogen-Induced Cracking · Stress Corrosion Cracking
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.