The influence of artificial saliva on NiTi orthodontic wires: a study on surface characterization

Ni and Ti based alloys are prospective materials for dental orthodontic wires because of their superior mechanical properties and corrosion resistance. The studies on the corrosion resistance of these materials according to their surface characterization in artificial saliva are limited. In this study, the changes on the surface of NiTi alloy based orthodontic wires in F– and PO³₄– added or not added artificial saliva after a period of time were investigated by SEM and EDS studies.Сплави на основі Ni та Ті – перспективні для виготовлення ортодонтичних дротів завдяки своїм високим механічним характеристикам та корозійній тривкості, яка у синтетичній слині методами поверхневого аналізу досліджена недостатньо. Вивчено зміни властивостей поверхні ортодонтичних дротів із нікельтитанового сплаву під час витримки в синтетичній слині з додаванням F– та PO³₄– та без них за допомогою сканівної електронної мікроскопії (SEM) та енергодисперсійного мікроаналізу (EDS).Сплавы на основе Ni и Ті – перспективные для изготовления ортодонтичных проводов благодаря своим высоким механическим характеристикам и коррозионной стойкости, которая в синтетической слюне методами поверхностного анализа исследована недостаточно. Изучены изменения свойств поверхности ортодонтичных проводов из никельтитанового сплава во время выдержки в синтетической слюне с добавлением F– и PO³₄– и без них с помощью сканирующей электронной микроскопии (SEM) и энергодисперсионного микроанализа (EDS)

Tribological Characterization of Al-bronzes Used as Mold Materials

Among the copper based alloys, Cu-Al-X bronzes are commonly used as mold materials due to their superior physical and chemical properties. Mold materials suffer from both wear and corrosion, thus, it is necessary to know which one of the competitive phenomenon is dominant during the service conditions. In this study, tribo-corrosion behavior of CuAl10Ni5Fe4 and CuAl14Fe4Mn2Co alloys were studied and electrochemical measurements were carried out using three electrode system in 3.5 % NaCl solution in order to evaluate their corrosion resistance. In tribo-corrosion tests, alloys were tested against zirconia ball in 3.5 % NaCl solution, under 10N load with 0.04 m/s sliding speed during 300 and 600 m. The results indicate that (i) CuAl10Ni5Fe4 alloy is more resistant to NaCl solution compared to CuAl14Fe4Mn2Co alloy that has major galvanic cells within its matrix, (ii) although CuAl10Ni5Fe4 alloy has lower coefficient of friction value, it suffers from wear under dry sliding conditions, (iii) as the sliding distance increases, corrosion products on CuAl14Fe4Mn2Co surface increase at a higher rate compared to CuAl10Ni5Fe4 leading to a decrease in volume loss due to the lubricant effect of copper oxides

Microstructural and Mechanical Characterization of Solidified Austenitic Stainless Steels

Among the family of stainless steels, cast austenitic stainless steels (CASSs) are preferably used due to their high mechanical properties and corrosion resistance. These steels owe their properties to their microstructural features consisting of an austenitic matrix and skeletal or lathy type δ-ferrite depending on the cooling rate. In this study, the solidification behavior of CASSs (304L and 316L grades) was studied using ThermoCalc software in order to determine the solidification sequence and final microstructure during cooling. Theoretical findings were supported by the microstructural examinations. For the mechanical characterization, not only hardness measurements but also tribological studies were carried out under dry sliding conditions and worn surfaces were examined by microscopy and 3D profilometric analysis. Results were discussed according to the type and amount of microstructural features

Microstructural and Tribological Characterization of Aluminium Bronzes with Additions of Si and Cr

The article presents the investigation results of the crystallization (performed by means of the TDA method) and the microstructure of complex aluminium bronzes with the content of 6% Al, 4% Fe and 4% Ni, as well as Si additions in the scope of 1–2% and Cr additions in the scope of 0.1–0.3%, which have not been simultaneously applied before. For the examined bronze, the following tests were performed: hardness HB, impact strength (KU2). For bronze CuAl6Fe4Ni4Si2Cr0.3, characterizing in the highest hardness, wear tests were conducted with dry friction and the dry friction coefficient. The investigations carried out by means of the X-ray phase analysis demonstrated the following phases in the microstructure of this bronze: αCu, γ2 and complex intermetallic phases based on iron silicide type Fe3Si (M3Si M={Fe,Cr,…}). Compared to the normalized aluminium bronzes (μ=0.18–0.23), the examined bronze characterizes in relatively low wear and lower friction coefficient during dry friction (μ=0.147±0.016)