February 12 2021 LC & GC Chromatography
We get lots of questions about whether we're able to coat small parts for micro precision instruments or micro GC applications. Let's review common concerns and performance data.
The SilcoTek® Technical Service Team is here to help customers understand how to use, maintain and design for the use of our coatings in their process or products. We get lots of questions about the physical properties and limitations of our coatings. The more a customer understands how to properly employ and maintain coated surfaces in their process, the better the coating will perform throughout the life of the product or process. With that in mind, here are a few of the more common questions about how our coatings impact part design, fabrication, and installation.
Want to test our coatings in your application? Where here to help! Our R&D team is here to help test our coatings under conditions that best match your application. We'll even give you free coated test coupons! There's no obligation of course!
In this blog post you will learn:
Here are some common questions asked by our customers.
Generally no. We're able to coat precision components like micro GC columns or lab on a chip components. There are several variables that determine thickness, but all SilcoTek coatings in current production are deposited at < 3 micron thicknesses. The ability to change the coating thickness means that we're able to select the right coating thickness for your application. For example, SilcoTek is able to coat precision 0.5um filters with minimal impact to filtration performance. Please contact us to discuss thickness specifications.
SilcoTek coatings conform to the microstructure of the part surface. There is minimal filling of voids or change to the overall surface roughness. Overall roughness measurement may be reduced slightly (1-2 RA reduction), but not a significant change in roughness. Some SilcoTek coatings have a higher lubricity than stainless steel, so even though surface roughness has not changed, the surface may have a lower friction coefficient.
Yes! SilcoTek coatings are proven to withstand compression and shear stress common to CF, face seal, and threaded sealing systems. The SEM (Scanning Electron Microscopy) images below show in detail the before and after effects of sealing on SilcoTek coatings. The example below shows the effects on a face seal surface after making a leak tight seal.
|FESEM (Field Emission Scanning Electron Microscopy) image of the coated pre-sealed surface shows the coating conforms to the sealing area. The raised surfaces of the face seal gland area can be seen. SilcoTek coatings conform to surface contours and small orifices.
|After making the metal-to-metal face seal per manufacturers instruction, a second FESEM image of the post sealing surface shows no scarring or scratching, only trace particulate from the silver gasket.
SilcoTek does not recommend coating ferrules, we've found this may lead to leaking problems after coating.
SilcoTek can coat intricate parts and small bore tubing. For example we're able to coat sample needles and components with blind holes or narrow passages. How do we do it? We our process involves specialty gases that are able to penetrate small or intricate openings. We're even able to coat fritted materials. The image below shows a sectioned fritted metal filter after coating. You can see how our process gases are able to penetrate the filter and coat internal surfaces.
Often precision instrumentation or micro GC applications require some exposure to elevated temperatures. In general our coatings tolerate low and high temperature exposure very well. Temperatures should not exceed the recommendations below in order to maintain the coatings' specified performance properties, but coated parts can be used at higher temperatures under certain conditions. Heat treatment of parts at the application's temperature will ensure the best results if exceeding the temperature limits suggested below. Please contact technical support for additional information or to discuss your application.
Watch our heat resistance video to see how our coatings perform under extreme heat:
SilcoTek® coatings are stable to the following temperatures in an inert atmosphere:
*The values below reflect limits of the coating material itself and assume that the base substrate is stable at these temperatures.
|450 °C; 400 °C (oxidative atmosphere)
|450 °C (functionalization loss), 400 °C (oxidative atmosphere), 1410 °C (melting)
|500 °C; 450 °C (oxidative atmosphere)
Depending on the coating, wear resistance can be increased. For example Dursan® will double the wear resistance of stainless steel. The SilcoNert® coating will not significantly improve wear resistance. Dursan will reduce sliding friction and can be used for light duty applications involving wear or sliding, like in a slider valve or cylinder bore involving elastomeric seal contact.
Most alloys of stainless steel, exotic alloys (except some duplex steel alloys), ceramic, and most glass materials can be treated. Some other metallic materials, such as nickel, brass, and copper, are incompatible with the 400+°C temperatures used in the process, and should not be treated. Go to our material compatibility chart for a complete listing of material that can and cannot be coated, or contact our team to discuss your application.
Note: carbon steel, F22 or similar carbon steel, is not recommended for coating in corrosion resistant applications. Treated carbon steel may rust in corrosive environments. Avoid corrosive environments when using treated carbon steel in inert sampling applications.
SilcoTek® can coat aluminum substrates however there are limitations for components used in high stress applications. Go to our aluminum coating page to learn more about aluminum coating capabilities. Contact us to ensure optimal processing of your aluminum parts. Want to learn more about coating metal parts? Read our materials blog post.
Welding will remove the SilcoTek coating ~2-4mm in all directions from the heat affected zone. SilcoTek can coat over high-quality welds, such as those listed in our material compatibility guide.
Read a Technical Insight from SilcoTek's R&D group regarding coating of brazed and soldered components.
We recommend vacuum brazing or welding of joints for best coating quality. Vacuum brazing is a high temperature, flux-free brazing process that results in a contamination-free joint. SilcoTek recommends vacuum brazing services from Solar Atmospheres Inc.
If you have more questions about factors that influence part design and use of our coatings or want to get more CVD coating information, you can chat directly with a member of our Technical Service Team. Our chat is open weekdays from 9:00 am until 5 pm. Or follow us on LinkedIn.
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