Direct Part Marking and Its Affect on Material Properties

The need to create surface modifications in the form of laser marking, while producing little or no increase in the fatigue deficit of the part, has recently become paramount in the aerospace industry.  With the advent of DoD mandate (MIL-STD-130) for serialization and part identification in the form of a two-dimensional Unique Identifier (UI), and under the guidance of NASA (NASA-STD-6002 and NASA-HDBK-6003), the NALI Laser Applications Laboratory at CCAT has begun an effort to identify the effects that direct part marking by laser has on materials used specifically in the aerospace industry.  CCAT has developed a program that takes a systematic approach to laser marking whereas the effects on the material are cataloged based on mark type (etch, machining and annealing) as well as shape and depth of the studied features.  Unlike traditional mechanical marking processes such as dot-peen, the laser is a non-contact marking method.  As such, the residual stresses from the formation of the mark are very different.

Top view of a 20-watt fiber laser mark on a magnesium alloy, as measured with 3D microscope that shows the mark depth profile measurements.  The 3D microscope has the ability to perform non-destructive measurement and evaluation of laser processed components.

A key aspect of this program is documenting and understanding how the laser marks affect the base materials under various conditions with a multitude of geometries, not simply to produce a single workable feature on a case by case basis.

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