Is LIBS non-destructive ?

Is Laser-OES Non-Destructive? Exploring the "Near-NDT" Nature of Laser-Based Analysis

In modern materials testing, maintaining product integrity while obtaining accurate, in-depth data is crucial. Laser-OES, or Laser Optical Emission Spectroscopy, has become a valuable tool in various industries for fast, accurate elemental analysis. But an essential question remains: Is Laser-OES non-destructive? In this article, we’ll explore how Laser-OES works, its impact on the materials it tests, and why it’s often referred to as a "near-nondestructive testing" (near-NDT) method.

Understanding Laser-OES Technology

Laser-OES is a type of spectroscopy that leverages a focused laser to vaporize a minuscule amount of material from the sample's surface. When the laser hits the sample, it creates a plasma containing ionized particles from the sample’s surface. The excited atoms in the plasma emit light at specific wavelengths, which are characteristic of the elements present in the material. By analyzing the emitted light, Laser-OES can provide a detailed breakdown of the sample’s elemental composition.

This technique offers several advantages:

• Speed: Measurements are rapid, often taking only a few seconds.
• Precision: Laser-OES can detect elements in low concentrations.
• Portability: Many Laser-OES devices are compact, allowing for on-site, in-situ testing.

However, like any other method involving vaporization, Laser-OES leaves a mark on the tested material, making the question of its destructiveness more complex. Specifically in the world of metals this topic has high relevance, whereas in minerals and other materials the effect is neglectable.

The Concept of "Micro-Burnspot" and Material Impact

The primary indicator of Laser-OES’s impact on a material is the "burnspot," or ablation mark, created when the laser interacts with the surface. In some products, this burnspot is referred to as a "micro-burnspot" because of its minimal size—typically around 0.1 mm in diameter. Such a small mark is often barely visible and may not affect the material's integrity or function.
Many burnspots only become visible after same time, when they oxidize. In bright non-ferrous materials they remain widely invisible.

The penetration depth of the laser also factors into the non-destructive nature of Laser-OES. Generally, penetration depth depends on the laser's wavelength, pulse energy, and material properties, but it is usually limited to the surface micrometer range. This shallow depth ensures that only the surface layer is affected, leaving the bulk of the material untouched.
At QuantoLux products like the portable QLX1 or bench top QLX3, multiple pulses are used to hit the same spot, creating a similar appearance as the known burnspots from spark-OES, just way smaller. 

Is Laser-OES Non-Destructive?

Strictly speaking, Laser-OES cannot be classified as a completely non-destructive testing (NDT) method, because it requires some material removal to generate the plasma for analysis. However, the micro-burnspot left behind is often so tiny and shallow that it has minimal impact on the material's structural properties, mechanical strength, or overall usability.

For most practical purposes, the term "near-NDT" is more appropriate. Here’s why:

1. Minimal Surface Impact: The diameter of the micro-burnspot is exceptionally small—only about 0.1 mm—and typically only affects the outermost layer of the material.
2. No Impact on Bulk Properties: The laser’s penetration is shallow enough that the bulk of the material remains unaffected, preserving its core properties.
3. Negligible Alteration: Especially for applications like alloy verification, quality control, and sorting, the minimal burnspot is unlikely to compromise the material's appearance, function, or longevity.

In many industries, this "near-NDT" nature of Laser-OES is adequate to ensure that the materials being tested meet regulatory and operational standards without significantly altering the material itself.

Applications of Laser-OES as a Near-NDT Technique

The near-NDT characteristics of Laser-OES make it highly valuable in fields where both precision and minimal invasiveness are required. Common applications include:

• Metals and Alloy Analysis: Laser-OES is extensively used in the metallurgy industry for verifying the composition of metals and alloys without damaging the parts or products.
• Quality Control in Manufacturing: In industries where rapid analysis is essential, Laser-OES provides accurate data on material composition with minimal material impact, allowing manufacturers to perform checks without damaging final products.
• In-Field Testing: Portable Laser-OES devices allow for on-site testing in industries like aerospace, automotive, and power generation, providing detailed elemental analysis without compromising component functionality.

Advantages of Laser-OES in Near-NDT Applications

The near-NDT nature of Laser-OES offers a unique blend of benefits that make it highly suitable for many quality control and verification tasks:

1. High-Precision Analysis: Laser-OES offers an accurate breakdown of elemental composition, essential for meeting industry-specific standards.
2. Minimal Material Damage: The micro-burnspot, with a typical diameter of 0.1 mm, has minimal impact on the overall structure and is often invisible to the naked eye.
3. Small Samples & prep-free: Analyzing small sample like screws, wires, chips, etc. is easily possible without special calibrations and without special sample preparation. Cleaning the sample surface is good enough for most metals.
4. high-quality results on bent surfaces: with portable devices or handheld, micro-burnspots help analyzing bent surfaces like tubes or pipelines without sacrificing analytical performance.
5. Fast, On-Site Capability: As a portable solution, Laser-OES enables companies to conduct rapid, reliable analysis without removing components from their operational setting.

Conclusion: Why Laser-OES Is Considered Near-NDT

Laser-OES represents a unique approach to material analysis, bridging the gap between destructive and non-destructive testing. While it does leave a tiny burnspot, the impact on the material is so minimal that it rarely compromises the material’s integrity, appearance, or function. Consequently, Laser-OES is commonly regarded as a "near-NDT" technique—offering the precision and detail of more invasive testing methods without the associated material damage.

This near-NDT classification makes Laser-OES invaluable in various industries where accuracy, speed, and minimal invasiveness are paramount. From alloy composition verification to quality control, Laser-OES allows manufacturers and engineers to test without disrupting. For most practical applications, the micro-burnspot’s size and shallow penetration render this technique as close to non-destructive as possible, making it an excellent choice for sensitive and precision-based testing environments.