Optimization of a Rotating Twin Wire-Arc Spray Gun

Abstract

Abstract The replacement of cast iron sleeves through thermal spray coatings is an interesting alternative to improve the inter bore reliability, to reduce weight and to reduce the inter bore distance for automotive engines. Most of the actual production and pilot equipments use the ROTAPLASMA process to provide such functional coatings. However, the wire-arc spray process may often present different advantages like a higher deposition rate and a lower cost of the produced coatings. The LDS (Lichtbogendrahtspritzen) technology developed by DaimlerChrysler is a wire-arc process working with two wires whereas the PTWA (Plasma Transferred Wire Arc) process designed by Flame Spray Industries and the Ford Motor Company use a single wire. The present paper shows that the wire-arc technology may replace efficiently the APS (Atmospheric Plasma Spray) for the generation of thermally sprayed coatings applied on engine cylinder bores. A first rotating wire-arc spray system was previously designed and tested a few years ago. The present paper shows how computational fluid dynamic (CFD) may help in solving industrial problems: the FLUENT CFD code was used in order to perform improvements of the initial gun design.