New nitriding system helps FA Krosno strengthen long-term cooperation with Nitrex

The new FA Krosno Nitrex system allows for a shorter process time and improved energy efficiency. (Courtesy: Nitrex)

FA Krosno completed the installation of a Nitrex nitriding system at the manufacturing facility in its namesake city in southeastern Poland.

The company is one of the largest players in the European gas springs market supplying manufacturers of commercial vehicles and agricultural equipment such as Fiat SpA, Scania AB, MAN SE, and AGCO.

Over the last several years, FA Krosno, a European leader in automobile parts manufacturing, and Nitrex have entered into a research and development initiative to improve the durability of piston rods in gas spring assemblies of passenger vehicles. The piston rod is the highest stressed part of the assembly and is subject to buckling, which adversely impacts the service life of the gas spring. The challenge was to design a nitriding cycle that would achieve a high surface hardness for improved wear resistance and minimized friction, and which would ultimately extend the service life of the gas spring.

“Where collaborating suppliers are concerned, FA Krosno places strict technical, quality, process, and environmental demands on suppliers. We are extremely proud to count ourselves among the company’s preferred suppliers,” said Marcin Stoklosa, special projects manager of Nitrex Metal. “Nitrex nitriding technologies were recognized as the best performing and best suited to the application’s requirements. Results from various metallurgical and mechanical tests conducted on the nitrided piston rods confirmed that the desired thickness of the white layer, the oxide thickness of the white layer, corrosion resistance, as well as the appropriate roughness were consistently obtained after Nitreg® nitriding and was maintained even after subsequent finishing operations.”

Production with the new system started in December 2019. The Nitrex system, pit-type model NX-1220, has overall chamber dimensions of 2,184 mm diameter by 3,452 mm high (86” x 136”) with a capacity to nitride a 3,800 kg (8,400 lb.) load. The delivered solution includes dual technologies, Nitreg®, and ONC®, the latter being a post-nitriding oxidation process that further enhances the quality of the nitride layer, provides additional corrosion protection, and similarly contributes to the aesthetic finish of the piston rods. The new system replaced a defunct gas nitrider that was phased out due to inconsistent results and high scrap losses. Besides overcoming these challenges, the new Nitrex system also allows for a shorter process time and improved energy efficiency.

Another interesting part of the project was the design of a customized racking fixture. Conceived and designed in collaboration with FA Krosno and Nitrex engineers, this unique multiple-purpose fixture combines stackable bases that can be configured for use in pre-nitriding, nitriding, and post-nitriding operations. The flexible arrangement allows for easy assembly and disassembly and facilitates the transfer between the various finishing stages of the piston rods without the need to manually reposition parts.