Karakterizacija biorazgradljivih zlitin iz sistema Fe-Mn sintetizirane s selektivnim laserskim taljenjem

Kraner, Jakob (author), Godec, Matjaž (mentor), Paulin, Irena (comentor), Medved, Jože (comentor)

Nepogrešljiva prisotnost kovinskih materialov v medicinskih aplikacijah je z najnovejšimi izzivi in trendi prehoda iz stalnih na začasne implantante bila razširjena tudi na raziskovanje biorazgradljivih kovinskih materialov. Glede na pomanjkljivosti prepočasne razgradnje zlitin na osnovi Fe, se dodatek Mn ter posledično zlitine iz sistema Fe-Mn obravnavajo kot ene najbolj perspektivnih za izdelavo in kasnejšo uporabo v želenih aplikacijah za medicinske namene. Pri ustvarjanju in razvoju novih zlitin in izdelkov iz navedenega binarnega sistema, ki bi izkazovali za telo neškodljivo in povečano stopnjo razgradljivosti, smo glede na ustvarjalne prednosti dodajalnih tehnologij izbrali selektivno lasersko taljenje. Z raziskavami smo v prvi vrsti dokazali razlike med uporabo mehansko mešanih elementarnih kovinskih prahov in predhodno izdelanimi zlitinskimi kovinskimi prahovi. Hitrost napredovanja korozije kot tudi raztapljanje izdelkov iz primerjanih kovinskih prahov izdelanih s selektivnim laserskim taljenjem v različnih medijih lahko ocenimo kot povsem primerljivo. Z omogočenim načinom spreminjanja obratovalnih parametrov (moč laserja in hitrost vrstičenja) in obsežno karakterizacijo materiala smo izdelali procesna okna, ki so nam služile za ugotavljanje vpliva in optimizacijo parametrov, kar je vodilo v izbiro najugodnejših obratovalnih parametrov za povečanje reakcijske površine in posledičnega hitrejšega napredovanja korozije. Iz potrebe po prekrivanju premera laserskega snopa in medlaserske razdalje smo izpeljali novo enačbo za izračun gostote vnesene energije. Za podrobno analizo in ugotovitev vpliva procesnih parametrov smo primerjali tudi vzorce izdelane z enako vneseno gostoto energije vendar uporabljenimi različnimi vrednostmi moči laserja in hitrosti vrstičenja. Kljub opaženemu splošnemu upočasnjevanju hitrosti napredovanja korozije ob dodatku Ag nam je s Fe-Mn-Ag zlitino in s skoraj polovično vrednostjo ustvarjene poroznosti uspelo izdelati material s hitrostjo korozije kar 1775,22 µm/leto.

• Language: Slovenian
• Keywords: biorazgradljive zlitine FeMn, selektivno lasersko taljenje, procesni parametri, karakterizacija materialov, hitrost korozije
• Work type: Doctoral dissertation
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2021
• PID: 20.500.12556/RUL-133749
• COBISS.SI-ID: 87448067
• Publication date in RUL: 14.12.2021

Secondary language

• Language: English
• Title: Characterization of biodegradable alloys based on Fe-Mn synthesized by selective laser melting

Abstract

With the current trends to make a transition from permanent to temporary medical implants, the indispensable presence of metallic materials in medicinal applications has been extended to the research of biodegradable metallic materials. Taking the disadvantages of slow decomposition of Fe-based alloys into account, the addition of Mn and consequently alloys from the Fe-Mn system is considered one of the most promising for manufacturing and subsequent use in applications for medical purposes. In the creation and development of new alloys and products from the above binary system, which would show an increased degree of degradability, we have chosen a selective laser melting due to the creative advantages of additive manufacturing. Through our research, we firstly demonstrated the differences between the use of mechanically mixed elemental metal powders and prefabricated alloy metal powders systematically. The rate of corrosion progression as well as the dissolution of products from the compared metal powders made by selective laser melting in different media can be assessed as entirely comparable. With the ability of modifying the operating parameters (laser power and scanning speed), we created process maps at different levels of material characterization, which served us to determine the impact and optimize the parameters. It all led to the selection of the most favorable operating parameters to increase the reaction surface and consequently to a faster progress in corrosion. From the need to overlap the laser diameter and the hatch distance, we have derived a new equation to calculate the input energy density. For a more detailed analysis, and to determine the impact of process parameters, we have also compared the samples manufactured with the same input energy density but using different laser power and scanning speed combinations. Despite the general inhibition of the corrosion rate with the addition of Ag, we have managed to produce a material with as much as 1775.22 μm /year with FeMnAg alloy and almost half the value of the generated porosity.

• Keywords: FeMn biodegradable alloys, selective laser melting, process parameters, materials chraracterization, corrosion speed