X-ray fluorescence (XRF) spectrometry is a non-destructive, non-invasive testing procedure, employed to verify and identify the chemical composition of solid, liquid, and powder metal coatings and alloys. Reducing the cost and size of XRF instruments has been a crucial focus of developments in this technology.
In 2015, the commercial launch of Tribogenics’ triboluminescence technology was a big step in the field of XRF technology, as it reduces the usage cost of XRF technology by almost half, without compromising the capability (Figure 1).
The users who initially benefited from the development are machine shop operators, who were able to add or transition to on-demand use of the XRF spectrometry for their processes. This article presents the benefits Plasma Technology (PTI) experienced when transitioning from batch-basis usage of XRF spectrometry to on-demand use.
The surface engineering services provided by PTI include custom tailored precision coatings with different combinations of properties, such as cost, weight, hardness, and also electrical, corrosion, and thermal resistance of the base materials, which improve the lifespan of the parts. PTI began making aircraft segments, however non-aircraft segments account to roughly 60% of its current market.
PTI provides more than 300 coatings that are applied using eight different techniques. These include Combustion Coating, High Velocity Oxy-Fuel Coating (HVOF), Wire Arc Coating, and Plasma Coating.
As standard in many job shops, many departments in PTI are required to carry out positive material identification (PMI), but the cost of having an XRF instrument in-house outweighs the total number of XRF measurements carried out each year. Previously PTI would use a mobile XRF spectrometer on lease twice a year after they were able to batch together adequate measurements to cover the lease cost.
The customers send their parts to PTI, and the coating is applied. As the received parts may pass through multiple companies before reaching PTI there may be a discrepancy between the items received and the paperwork, as a metal could of been changed in the upstream process, but this may not be accurately reflected in the part’s documentation.
Quality control (QC) should be able to positively verify the material composition of the part, as the process for each coating should match the material of the part. The use of an XRF spectrometer allows the QC staff to rapidly identify such discrepancies between the part and the paperwork, and prevent the application of an unsuitable coating, enabling the application of accurate coatings, especially when applying different multiple coatings on the same part.
PTI’s surfacing services are supported by the part-specific tooling and equipment manipulators created by the tooling group, who typically use titanium, steel, and aluminum alloys. Making sure that the metal alloys do not interfere with the coating process is a crucial step, because the markings used to identify the metal alloy stock are often cut off upon usage of the stock, which can lead to unintentional misidentification of the stock. The use of an XRF spectrometer ensures that the staff confidently select and use the appropriate stock for each part (Figure 2).
Novel coating materials are developed by the research and development group at PTI according to the customers’ requirements. Coating formulations include powders of different materials that are mixed and blended together. It is crucial to ensure that different powders are mixed properly because of the manner in which the resulting powder mix is sprayed on a part.
The XRF spectrometers are highly suitable to positively verify if the powders are mixed consistently to the required proportions, if the coatings are accurately applied onto the coupons, and if the correct bond slugs and coupons are used for testing.
When the coatings are applied using a grit blasting technique a considerable amount of coating powder is transformed as dust waste, which is collected from the spray booths, deposited in barrels, and ultimately recycled. As is takes many jobs to fill a barrel, keeping track of the dust deposited in each barrel is necessary.
If an incompatible or a low value metal is routed to a barrel with metal dust of a high value, then the money recovered through recycling will be reduced. The use of an XRF spectrometer not only enables the plant manager to correctly track the barrel contents and schedule the filling of appropriate metal dust, but also provides him with the knowledge of the barrel composition before sending it for recycling.
As PTI carries out nearly 100 XRF spectrometry measurements in a year, owning a XRF instrument was not justifiable.
PTI would lease an XRF spectrometer for a single day after collecting an adequate number of barrels to process to justify the cost.
The overall cost of collecting and storing the barrels until a complete batch is complete was incurred by the plant manager. While leasing an instrument, additional costs were also incurred in terms of traveling to collect and return the instrument.
Other departments would schedule measurements using the XRF instrument during the same lease window, but sometimes there would not be enough time to complete all the required measurements in a single day. This means the company would incur a second day of rental cost.
Tribogenics’ Watson XRF spectrometers can be purchased for nearly half of the cost of traditional hand-held XRF spectrometers. As the Watson instruments utilize triboluminescence to produce X-rays, they offer capabilities similar to the highly expensive units but at a comparatively lower cost.
PTI has determined that the new Watson™ hand-held XRF analyzer is easy to learn, operate, and use. This inexpensive XRF device is available in the market at a price point that is less than half that of older units.
When operators carry out multiple scans, they do not have to stop after each reading and write the result down as Watson™ records multiple readings, sends a sequential report to the user’s computer using the Wi-Fi feature, and generates reports within a few seconds. Watson also provides free cloud storage for a year.
In addition to all of the above features, Watson™ is a first of its kind hand-held XRF analyzer that is embedded with a field exchangeable X-ray cartridge that can be swapped in the field within a few seconds, which means there is no downtime.
PTI came to the conclusion that the value of replacing batch measurements with on-demand measurements at the price point of the Watson XRF spectrometer warranted buying Watson™ units for its California and Connecticut sites.
Steve Norris, Director of Quality, Plasma Technology, Inc.
Stewart Chalmers, VP of Marketing, Tribogenics.
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