Analyzing Stainless Steel and High Temperature Alloys Using LIBS

Alloy analyzers based on laser-induced breakdown spectroscopy (LIBS) are gaining popularity in scrap metal sorting applications, thanks to their numberous advantages, including low maintenance costs, lack of costly detectors and tubes to replace, and rapid analysis of aluminum alloys, titanium alloys and red metals.

The absence of X-ray radiation in these analyzers makes the regulatory situation vastly simpler, with no need to obtain monthly badges or have visits from regulators, which many scrap recycling plants find to be an important benefit.

Challenges for LIBS: Stainless Steel and High-Temperature Alloys

Analysis of real-world stainless and high temperature alloys was difficult to achieve using early laser-based analyzers, due to the difficulty of creating plasmas from these refractory materials.

One good example that illustrates this difficulty is the differentiation of stainless steel 304 from stainless steel 316 by detecting the 2% molybdenum (Mo) present in 316.

The development of the Pulsar laser by SciAps has overcome this challenge, by delivering 5-6 mJ of energy in each pulse, condensed into a very small focal area, in a time duration of around 1 nanosecond. This high energy density results in higher-temperature plasmas, thus providing much improved analysis of refractory metals compared to early handheld LIBS analyzers. In combination with the patent-pending, wide-range, high-resolution sensor, LIBZ instruments from SciAps are strong competitors to X-ray analyzers.

SciAps LIBZ unit – SciAps Z-100

Figure 1. SciAps LIBZ unit – SciAps Z-100

Detection of Mo Signal by LIBZ

As discussed above, testing of stainless steel 316 for Mo is good example to demonstrate the capabilities of the new Pulsar laser technology from SciAps.

Figure 2 shows the spectrograph obtained from a 316 sample in just a few seconds, with clear signals from Mo. LIBZ uses the 550nm spectral region for measurement of Mo. This is in contrast to earlier LIBS instruments - these used the 386nm region, which is prone to interference from iron.
Mo lines in 316 Stainless

Figure 2. Mo lines in 316 Stainless

Based on this breakthrough laser technology, SciAps has introduced an effective new sorting technique for stainless steel alloys.

The Mo response of combined 300, 400 and Duplex type stainless was shown in Figure 3. The nickel response was illustrated in Figure 4. Both the responses indicate an improved correlation which proves that LIBZ is an inexpensive, versatile and hassle-free alternative solution to x-ray fluorescence analyzers.

Mo response in combined 300, 400 and Duplex type stainless

Figure 3. Mo response in combined 300, 400 and Duplex type stainless

Nickel response in combined 300, 400 and Duplex type stainless

Figure 4. Nickel response in combined 300, 400 and Duplex type stainless

Detection of Ni Response

Nickel alloys are highly refractive materials that are a challenge to analyze using LIBS, due to the high temperatures needed to convert them to a plasma. For this reason, nickel alloys have been a strong application for X-ray techniques to date.

However, the recent advancements in LIBZ technology make it suitable for analysis of most Ni, Co, and Ni/Co alloys. The Ni response curve for Ni alloys ranging from 35% Ni to Ni 200 is shown in Figure 5. The figure shows an improved correlation, enabling rapid analysis of high temperature alloys.

Ni response curve for Ni alloys

Figure 5. Ni response curve for Ni alloys

Summary

Laser-induced breakdown spectroscopy, which is used in the range of handheld LIBZ analyzers from SciAps, is a safe and high performance alternative to X-ray analysis, which offers hugely reduced regulatory requirements. LIBS is becoming well known as a high-performance analysis technique for Ti, Cu and Al alloys, and red metals. This makes it highly attractive for users in the scrap metal recycling industry.

Now, SciAps have introduced advancements in their laser technology, which enable high-performance analysis of all metals, including stainless steels and high-temperature alloys.

Contact SciAps for more information

This information has been sourced, reviewed and adapted from materials provided by SciAps, Inc.

For more information on this source, please visit SciAps, Inc.

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