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Brodski vijak ili brodski propulzor je dio broda koji pretvara energiju vrtnje brodskog pogonskog vratila u hidrodinamičku silu pogona broda. To se postiže rotacijskim gibanjem krila brodskog vijka kroz morsku ili slatku vodu. U ovom završnom radu prikazan je pregled povijesnog razvoja brodskog vijka, karakteristika porivnih sustava brodova manje i srednje veličine te pregled različitih vrsta materijala od kojih se izrađuju brodski vijci za navedene veličine pomorskih brodova. U eksperimentalnom dijelu rada je na pribavljenim dotrajalim pomorskim brodskim vijcima ispitan kemijski sastav materijala i utvrđena je mikrostruktura. Kemijski sastav je potvrdio da je riječ o aluminijskoj bronci legiranoj nikom i željezom, čime se postiže antikorozivnost ovog materijala u morskoj vodi. Prema normi je ispitana tvrdoća materijala te su potvrđene visoke vrijednosti tvrdoće čime će se postići manje trošenje i veća trajnost brodskog vijeka. Analiza mikrostrukture je pokazala karakterističnu dvofaznu mikrostrukturu aluminijske bronce legirane željezom i nikom, s alfa-fazom kristalima mješancima i s kapa-fazom intermetalnog spoja. Ship's propeller is part of the ship which transforms propeller shaft rotating energy into the hydrodynamic force that drives the ship. This is achieved by rotating movement of the propeller fin through sea or fresh water. This final thesis shows a review of ship screw historical development, characteristics of propulsion systems of small and medium size ships and a review of different types of materials used in the production of propellers for seagoing ships of previously mentioned sizes. The experimental part of this thesis examines the chemical composition of the material and determinates the microstructure of a used, worn out propeller. The chemical composition analysis has confirmed the aluminium bronze alloyed with nickel and iron, which achieves anticorrosive features in the sea water. The hardness of the analysed propeller was tested according to standards, and high hardness values were confirmed, which gives less wear and longer life of the ships screw. The microstructural analysis showed the characteristic two-phase microstructure of the aluminium bronze alloyed with nickel and iron, with the solid primary α-phase and with -phase as an intermetallic compound. |
