Swagelok develops new process to harden stainless steel
Apr 09, 2009
Steel users such as Swagelok haven't given up on value-added projects that reduce the cost and improve the quality of the metal products they buy and use in making valves and fluid and gas system components. Case in point: The self-developed Swagelok SAT12 process, a surface-hardening procedure that boosts basic stainless steel's surface hardness and wear and corrosion resistance to mimic the mechanical properties of titanium, Hastelloy and other specialty alloys.
Solon, Ohio-based Swagelok produces and sells more than $1.3 billion annually in high-quality products used in the instrumentation, pharmaceutical, oil and gas, power, petrochemical, alternative fuels and semiconductor industries.
Within Swagelok, there is a multi-functional Metallurgical Research and Development team which performs applied research for various product-manufacturing groups. In recent years, the team was responsible for the development of the SAT12 surface-treatment method that reduces throughput time and improves the mechanical properties of precision parts made into complex shapes and structures from austenitic stainless steel.
Previously, the company had bought expensive alloys to attain such key performance characteristics as wear resistance, surface hardness, fatigue resistance and corrosion resistance. Now, using the SAT12 process, also known as low-temperature colossal super-saturation (LTCSS) service, the company can use basic austenitic stainless steel as the substrate for eventual use as the source material for high-quality components. In the process, carbon is diffused interstitially into the lattice structure of the stainless steel. The result is stainless steel exhibiting tool steel-like hardness, nickel alloy-like corrosion resistance, high-levels of wear resistance, austenitic ductility, no distortion or dimensional change, no carbide formation and resistance to galling.
Most market applications use 300 Series grades of austenitic stainless steel but further field research has found that the SAT12 treatment of 316 Series of stainless steel can replace more expensive, exotic materials.
Senior research fellow Sunniva Collins has been charged with added research and evaluation that will lead to commercialization of the new technology. Swagelok has worked with Case Western Reserve University in Cleveland to help analyze the process, which also is a low-temperature case carburization process for tube fittings. This project is being co-funded with a $5.5 million grant from Ohio's Third Frontier Project, a state-funded program to turn high-tech research into home-market manufacturing.
Swagelok developed the process itself to heat-treat austenitic stainless steel rather than have it done by a stainless steel producer because surface science and metallurgy are core competencies of Swagelok. A corporate statement says that "the patented SAT12 treatment process still remains unique in how it achieves significantly increased tool steel-level surface hardness and retained corrosion resistance in the austenitic target materials." Additionally, the SAT12 process was developed to treat the back ferrule, a narrow circular ring of metal used for fastening, joining or reinforcement in the Swagelok tube fitting, a core product for company.
A corporate spokesman says that "the SAT12 process has its sweet spot where its application makes the greatest economic and technological sense." That's because complete processing can include cleaning and handling operations in addition to the low temperature carburizing treatment. So, end-product pricing is dependent on things like the condition of parts received, batch size, part configuration and mass. "Customers have found it cost effective because upon treatment, some corrosion-resistance properties of relatively low priced stainless steels have demonstrated the performance of more expensive, exotic alloys," he explains.
The majority of applications desire improved surface wear or scratch resistance while maintaining or improving corrosion resistance. So, currently, the SAT12 process is being used on Swagelok products used by the military and commercial marine, medical device, biopharmaceutical production and food production equipment.
