Influence of forming technological path on mechanical properties of steels for turbine blades

Namen magistrskega dela je bil ugotoviti vpliv tehnološke poti na mehanske lastnosti jekel za turbinske lopatice, v našem primeru jekel PK3Ni in PT929. Jeklo PK3Ni in jeklo PT929 sta martenzitni nerjavni jekli, ki se uporabljata predvsem za izdelavo turbinskih lopatic. Preoblikovali in toplotno obdelali smo ju po klasični ter modificirani tehnološki poti, ki se od klasične razlikuje v tem, da lahko s prilagajanjem temperature valjanja pri toplotni obdelavi izpustimo operacijo kaljenja. Opravili smo natezni preizkus, pri katerem smo določali natezno trdnost, mejo tečenja, kontrakcijo in raztezek. S Charpeyevim testom smo določali udarno žilavost, s trdoto po Brinellu pa trdoto materiala. Na podlagi rezultatov smo ugotovili, da vzorci, preoblikovani in toplotno obdelani po modificirani tehnološki poti, dosegajo podobne oziroma boljše rezultate kot vzorci, preoblikovani po klasični tehnološki poti. Pod svetlobnim mikroskopom smo opravili še pregled mikrostruktur, pri katerem smo ugotovili, da so te primerljive ne glede na izbrani tehnološki postopek.The aim of the master thesis was to determine the influence of the technological route on the mechanical properties of steels for turbine blades, in our case PK3Ni and PT929 steels. PK3Ni and PT929 steels are martensitic stainless steels mainly used for the production of turbine blades. The steel was transformed and heat treated according to the classical technological route and the modified technological route. The modified technological route differs from the classical route in that quenching during heat treatment can be omitted by adjusting the finishing rolling temperature. A tensile test was carried out in which tensile strength, yield strength, contraction and elongation were determined. The Charpy test performed was used to determine the notched impact strength of the samples. The hardness of both steels of the two technological routes was measured with the Brinell hardness test. Based on the results, we were able to determine that the samples formed and heat-treated according to the modified technological route achieved similar or better results than those formed according to the classical technological route. We also conducted an examination of the microstructures under the light optical microscope and found that the microstructures were comparable regardless of the technological method chosen