Handheld LIBS for Positive Material Identification: Better Than XRF?

If you’re a metal maniac like me, I’m assuming you know about handheld XRF and what a staple it is in Positive Material Identification (and if not, here’s a handy article about that).

But there is another method that is perfectly capable of doing many PMI testing applications for metal identification, and it is, without doubt, a super cost-effective option.

RIgaku KT-100S handheld LIBS analyzer

Is it better than XRF? Like everything else in life, it depends. Read on and make the call for yourself.

Unfortunately, there is a surprising amount of misinformation and confusion around this technology.

I thought it would be a good idea to dig in and cover everything that’s important to know about LIBS (specifically, handheld LIBS).

The obvious question to start with is:

What is handheld LIBS? Handheld Laser-Induced Breakdown Spectroscopy (LIBS) is the use of a laser rather than a spark or radiation to create light signature emissions that a detector and analyzer can use to determine the chemistry of a metal and provide alloy identification using a grade library.

In this article, we’re going to explore

• How does LIBS work?
• How long has LIBS been available?
• Why use handheld LIBS for PMI?
• How much does a handheld LIBS cost?
• Mistakes to avoid when using handheld LIBS
• Brands that manufacture handheld LIBS

Let’s get started!

Psst: This post is based on a podcast with co-host Chris Carolan. To hear this episode (and more like it), subscribe to The Manufacturing Show on Apple Podcasts, Spotify, or wherever you listen to podcasts.

iPhone Users Click Here for the Episode

The Rest Of Us Can Check It Out Here

How Does LIBS Work?

LIBS stands for laser-induced breakdown spectroscopy. It’s actually in the same family as OES (Optical Emission Spectroscopy). It just uses a laser instead of a spark.

LIBS diagram

How it works:

1. It burns and vaporizes the metal with a laser
2. This makes the elements in the material give off a light signature
3. The detector measures those light signatures
4. The analyzer determines the chemistry and makeup of the metal
5. It matches the percentages, chemistry, and composition against a grade library

This is how it’s able to tell you whether you’ve got stainless steel 316, aluminum 6061, aluminum 6063, Vibranium (just kidding; it doesn’t know Vibranium, but #WakandaForever).

Via HobbyLark

How Long Has Handheld LIBS Been Available?

Handheld LIBS has only been around for 7 or 8 years, but the technology itself is actually about fifty years old.

It's been limited to laboratory benchtop instruments, but new technological advances have made it possible to miniaturize the laser while keeping the performance high.

This is what makes it possible to use in a handheld format: the handheld LIBS you see today.

Today, LIBS is a perfectly capable tool used to do a lot of the things XRF can do in a handheld format, faster, and safer.

Sad plot twist: a combination of factors like over-promising and lack of training has led users to distrust in the technology when handheld LIBS first came out.

Why Use Handheld LIBS for PMI?

Let me tell you some of the advantages and disadvantages of using handheld LIBS to give you an understanding of why you might consider using it instead of a handheld XRF.

The pros of using a handheld LIBS analyzer for PMI

• It’s the fastest method of PMI testing. Alloy grade identification in 1-3 seconds.
• Measurement test times do not vary. No matter the metal being tested, test times will always be the same. This removes a key source of false positives and material mix-ups.
• No X-ray Radiation. Without ionizing radiation, there is no risk of accidental hazard exposure during testing.
• Less regulatory headaches. Most states and countries do not have strict regulation of LIBS analyzers.
• Better performance on light elements. Handheld LIBS is well-suited for elements like lithium (Li), beryllium (Be), magnesium (Mg), aluminum (Al), and silicon (Si)
• Lowest cost of ownership. A rugged design without expensive, fragile parts leads to less repairs and lower costs throughout the life of the handheld LIBS analyzer.

Advantages of handheld LIBS over handheld XRF

The cons of using a handheld LIBS analyzer for PMI

• Burns the surface of the metal. While it generally does not effect the mechanical integrity of the material, finished product specifications may not allow for the tiny burn mark left by a handheld LIBS.
• Training is often required to break XRF habits. While a handheld LIBS gun looks very similar to a handheld XRF gun, they are very different technologies. Users who try to use it exactly like an XRF may run into inconsistent results during initial testing.
• Direct contact with clean, base metal is required. This may require more sample preparation than a user is accustomed to. I review common mistakes related to this below.
• Lower precision at trace levels. While this always depends on the metal type and element being measured, it is generally advised to use handheld XRF or portable OES when high precision and accuracy is needed at the lowest levels.
• Not recommended for heavy alloys. Handheld LIBS is not well-suited for alloys like tungsten (W). It may be able to identify tungsten but it will have a tough time providing accurate values of other elements you may be looking for.

How Much Does A Handheld LIBS Cost?

Buying an analyzer will run you between $20,000 and $40,000. The reason for the wide range is that there are a group of LIBS analyzers that can test for carbon and sometimes even non-metals.

Those are closer to $40,000. The other group that does not analyze carbon will run in the $20,000 to $30,000 range.

 

Master Tip: If you don't need Carbon values, don't pay the premium for it.

Beyond the purchase price, the cost of maintenance and ownership is very minimal compared to handheld XRF and OES.

What you must spend money on:

• Swabs to clean the window of the analyzers on a regular basis.

Yes, that's it.

When you consider the lifetime cost of the instrument, these analyzers are likely the most cost-effective choice for PMI in the industry.

Common Mistakes to Avoid When Using Handheld LIBS

Without proper training or understanding, people can make mistakes with handheld LIBS. These mistakes have led to the misconceptions about the performance and viability of LIBS versus handheld XRF.

For the most part, it comes down to sample preparation.

On the one hand, you’ve got handheld XRF:

• Very forgiving
• You can have some surface contamination (but not much!)
• The prep doesn’t have to be perfect
• You don’t have to have perfect contact with the metal in order to get a result (results will vary more though)

On the other hand, with handheld LIBS:

• You need perfect contact
• A clean surface on the base metal is needed
• No rust or corrosion
• No dirty surface
• No coatings

All of this will get in the way. Sample preparation is very important and doesn't take as long as you think when done correctly.

With LIBS it’s very important to have a clean surface and to get perfect contact.

If you try to use it like a handheld XRF, you’ll probably produce inconsistent results because surface contaminants will have a bigger impact.

Sadly, a lack of training and understanding has led to these common mistakes. Beyond sample preparation, here are three extra tips to know so you can be a master at LIBS:

1. CLEAN - Ensure the analyzer window is clean
2. PREP - Ensure the sample surface has been prepared for testing
3. CONTACT - Ensure the sample surface is in complete contact with the analyzer
4.  

Brands That Manufacture Handheld LIBS

These are the current manufacturers of handheld LIBS instruments:

• SciAps - Ex. Z-50, Z-200
• Thermo Niton - Ex. Niton Apollo
• Hitachi - Ex. Vulcan Expert
• Bruker - Ex. EOS 500
• Rigaku - Ex. KT-100S
  • Note: Rigaku is the only brand that does not have a handheld XRF.

Unlike handheld XRF, there's not really a market leader for handheld LIBS yet. This is mostly due to its relative newness in the field.

LIBS Takeaways

Props for taking the time. You are now a Jedi when it comes to LIBS vs the other PMI methods!

Here are a few points I hope you got from this article:

• LIBS is the fastest and safest PMI technology available
• Proper LIBS training is crucial for positive results
• It's not XRF; don't use it like one
• If you train for it then you can reap the benefits of the faster and safer method
• LIBS has the lowest cost of ownership

Until next time, Never Stop Testing Your Metals!

For more information on positive material identification or LIBS, subscribe to The Manufacturing Show on Apple Podcasts, Spotify, or wherever you listen to podcasts.