| Popis: |
Osnovni cilj ovoga rada bio je opisati utjecaj mikrostrukturnih promjena na tribološka svojstva nehrđajućeg dupleks čeličnog lijeva oznake GX2CrNiMoN 25-6-3. U teorijskom dijelu rada opisana je korozijska postojanost čeličnih ljevova, njihova podjela i označivanje. Detaljnije su navedeni kemijski sastav, formiranje mikrostrukture i primjena dupleks nehrđajućih čeličnih ljevova. Također je opisan abrazijski mehanizam trošenja i faktori koji utječu na abrazijsku otpornost. U eksperimentalnom dijelu rada provedeno je ispitivanje otpornosti na abraziju, na uređaju Taber abrader, na dvije različite kvalitete brusnih papira, P220 i P500. Ispitivanje je provedeno na uzorcima sa izbalansiranom dupleks mikrostrukturom i na uzorcima kod kojih je žarenjem na 750 ˚C u mikrostrukturi formirana sigma-faza (~13%),smanjen udio ferita (~16%) i povećan udio austenita (~71%). Analizom rezultata utvrđeno je da formiranje sigma-faze u mikrostrukturi dulpeks nehrđajućih čeličnih ljevova smanjuje intenzitet abrazijskog trošenja i povećava tvrdoću lijeva. Također je utvrđeno da veličina abrazivnih čestica utječe na intenzitet abrazijskog trošenja. Utjecaj veličine abrazivnih čestica je jače izražen kod uzoraka bez sigma-faze. The main goal of this study was to describe the impact of microstructural changes on tribological properties of duplex cast stainless steel grade GX2CrNiMoN 25-6-3. In the theoretical part of this work, corrosion resistance, classification and designation system of the cast stainless steels were described. Chemical composition, formation of microstructure and application of duplex cast stainless steels were listed in detail. The abrasion wear mechanism and factors that affect abrasion resistance were also described. In the experimental part of this study, an abrasion resistance test was performed using the device Taber abrader with two different qualities of sandpaper, P220 and P500. The test was performed on samples with a balanced duplex microstructure and on samples in which the sigma-phase (~ 13%), reduced ferrite content (~ 16%) and increased austenite content (~ 71%) were formed in the microstrucure by annealing at 750 ˚C. The analysis of the results showed that the formation of the sigma-phase in the microstructure of dulpex cast stainless steel castings reduces the intensity of abrasion wear and increases the hardness of the cast iron. It was also found that the size of the abrasive particles affects the intensity of abrasive wear. The influence of abrasive particle size is more noticeable in samples without sigma-phase. |
