Characterization of a coating 316L applied by plasma transferred arc

Abstract

Parts of industrial machines and structures are often exposed to the action of aggressive environments, which in a short period of time can provoke the loss of their integrity. It is well known that for extending the service life against erosion and corrosion, protection of the exposed structure zone by coating is frequently used. Various application methods of protective coatings are applied, and the most common are welding and thermal spraying processes. The aim of this study was characterization of coatings made of stainless steel 316L, widely used in chemical and petrochemical industries. The coating was applied on a structural steel S235JR by plasma transferred arc using powder as a filler material. Due to a number of advantages, the plasma transferred arc (PTA) surfacing process has found significant usages in the field of surface protection. This paper presents results of hardness measurements in characteristic zones of the coating and the base material, as well as microstructural characterization of coatings using optical and scanning electron microscopy. Results of EDS analysis of the coating and hardness measurements indicated that a relatively high dilution (26.1 %) of the base material (BM) and the filler material (FM) occurred in a very narrow zone above the fusion line, and thus did not significantly affect the chemical composition of the rest of the coating. Also, erosion resistance tests of coatings were performed by changing the basic functional parameters that is the impact angle and the speed of erodent particles. It was observed that the erosion resistance of the coating material decreases approximately linearly with the increase of the particle speed. Also, with the increase of the impact angle of the erodent (up to 45 °), the mass loss of the coating material is increased.

Delovi mašina i konstrukcija su tokom rada izloženi delovanju agresivne radne sredine koja u kratkom vremenskom periodu može da naruši njihov integritet. U zavisnosti od radnih uslova, površina materijala može da bude izložena raznim mehanizmima oštećenja, od kojih se izdvajaju eroziona i koroziona oštećenja. Produžetak radnog veka ugroženih zona mašinskih konstrukcija moguće je izvesti različitim postupcima nanošenja zaštitnih prevlaka, a najčešće su to različiti postupci navarivanja i metalizacije. Cilj ovog rada je karakterizacija prevlake izrađene od nerđajućeg čelika klase 316L, koja je našla široku primenu u hemijskoj i petrohemijskoj industriji, nanete plazma postupkom navarivanja korišćenjem dodatnog materijala u obliku praha, na konstrukcioni čelik S235JR. U radu je izvršeno merenje tvrdoće u karakterističnim zonama prevlake i osnovnog materijala, kao i mikrostrukturna karakterizacija prevlake na optičkom i skenirajućem elektronskom mikroskopu. Takođe, izvršeno je eroziono ispitivanje prevlake promenom parametara ispitivanja, pre svega ugla nastrujavanja i brzine čestica erodenta.