Formation of nanostructured electrospark-alloyed coatings on the working surfaces of impulse face seals

Impulse face seals (IFS) are critical components of pumping and compressor equipment operating under high pressures, rotational speeds, and severe thermal and tribological conditions. The durability and reliability of IFS are largely governed by the properties of their working face surfaces, which motivates the development of advanced surface modification technologies. This study investigates the formation of nanostructured surface layers on Armco iron and HS6-5-2 tool steel by electrospark alloying (ESA) with a special technological medium (STM) containing single-walled carbon nanotubes (CNTs). The proposed processing route involved sequential ESA with a molybdenum electrode, application of CNT-containing STM, repeated ESA. The coatings were characterized in terms of microstructure, elemental distribution, surface roughness, microhardness, and wear resistance. Tribological tests were conducted under end-face friction against fluoroplastic, and real-life tests of an impulse gas face seal were performed to evaluate operational performance. The results demonstrate that adding 0.01 wt% CNTs to STM significantly refines the microstructure. A nanostructured coating with a microhardness of up to 1650 HV (for HS6-5-2 steel) was obtained, demonstrating more than a threefold improvement in wear resistance compared to coatings produced without the STM. Real-life tests confirmed stable sealing performance, low leakage, and a favourable thermal regime. The proposed ESA nanostructuring approach effectively improves the wear resistance and service life of impulse face seals in high-load compressors.