The evolution of the passive films on 2205 duplex stainless steel (2205 DSS) and AISI 316L stainless steel in artificial saliva, and with the addition of fluoride, was studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements. The extent of the passive range increased for the 2205 DSS compared to the AISI 316L in both solutions. The formation of the passive film was studied by EIS at the open-circuit potential (OCP). The passive layers were studied at the OCP by Xray photoelectron spectroscopy (XPS). The passive films on both materials predominantly contained Cr oxides, whereas the Fe species were markedly depleted.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 24275239In metal forming industry tools can be exposed to very complex and surface demanding conditions, which are the result of different effects (mechanical, thermal, chemical or tribological loading) and require well defined mechanical and especially tribological properties. The aim of the present work was to investigate the effect of deep-cryogenic treatment parameters (treatment time and temperature) in combination with plasma nitriding on the tribological performance of powder-metallurgy (P/M) high-speed steel. Special emphasis was put on abrasive wear resistance and resistance to galling under dry sliding conditions. Test results show that deep-cryogenic treatment contributes to improved abrasive wear resistance and better galling properties of P/M high-speed steel. Selection of the proper austenizing temperature is also an important factor, with higher austenizing temperature resulting in higher friction and wear. Plasma nitriding gives excellent tribological properties of P/M high-speed steel and reduces the effect of austenizing temperature. However, if combined with deep-cryogenic treatment it eliminates beneficial effect of deep-cryogenic treatment.
F.09 Development of a new technological process or technology
COBISS.SI-ID: 904106A study of oxide layers grown on 2205 duplex stainless steel (DSS) and AISI 316L autenitic stainless steel in simulated physiological solution is presented. The results of the potentiodynamic measurements showed that the extent of the passive range significantly increased for DSS 2205 comparing to AISI 316L stainless steel. Cyclic voltammetry was used to explain the electrochemical processes taking place on the surface of the investigated materials. The oxide layers formed by electrochemical oxidation at different oxidation potentials were studied by X-ray photoelectron spectroscopy, their compositions were analysed as a function of depth. The main constituents on both the investigated materials were Cr- and Fe-oxides. The AFM topography analyses illustrated the higher corrosion resistance of the DSS 2205 compared to the AISI 316L under the chosen experimental conditions.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 900522Zn-Al metallized film capacitors in two different production stages were investigated to explain the decrease of capacitors performance with time. Unsealed and sealed capacitors with different aluminium content in metallization layer were investigated. Scanning electron microscopy (SEM) was used to image the surface of the metallization layers, Energy dispersive X-ray spectroscopy (EDS) was used to determine the chemical composition and Auger electron spectroscopy (AES) was used to determine the chemical composition of the top of the metallization layers as well as to estimate the degree of oxidation. It was found that air humidity degraded the metallization layer of unsealed capacitors, especially at lower Al contents. A crystallographic explanation was proposed.
F.01 Acquisition of new practical knowledge, information and skills
COBISS.SI-ID: 953514The importance of selecting the right process parameters for ledeburitic tool steels, i.e., casting temperature, cooling rate, and soaking temperature, which is needed to improve their intrinsic hot workability, is presented. The results were obtained from investigations in industrial practice and in the laboratory. It was found that inappropriate selection of these process parameters results in the occurrence of carbides that are not usually present in these types of steels, in terms of type, shape, fractions, and their distribution that decreases the steels’ hot workability. In particular, a casting temperature that is too high and cooling rates that are too low result in the additional precipitation of carbides, which are not common in these steels, leading to cracking, predominately along these carbide stringers and consequently to a deterioration of the hot workability and the properties of the final products. It was also found that by selecting the proper soaking conditions, it is possible to decrease the negative influence of previous processing parameters on the hot workability.
F.10 Improvements to an existing technological process or technology
COBISS.SI-ID: 1206879