The Auger electron spectroscopy study on chemistry of the 46.8°(111) twist grain boundary of an Fe-2.3%V alloy showed an extended phosphorus enrichment at temperatures in range of 500°C and 800°C. Simultaneously, slight but nearly independent segregation of vanadium was also detected. The standard enthalpy and entropy of grain boundary segregation of phosphorus and vanadium were determined according to the Guttmann model of multicomponent interfacial segregation. Obtained data clearly show that this [sum] = 19 coincidence boundary is special (i.e. low energy interface). The data also fit well with the predictive model of grain boundary segregation and confirm that phosphorus segregates intersitially at the grain boundary while vanadium substitutes iron atoms in the interface structure.
COBISS.SI-ID: 899498
The application of a positive or negative local bias to the surface of La[sub]{1.975}Sr[sub]{0.025}CuO[sub]{4+[delta]} (LSCO) crystal by a conducting atomic force microscope tip results in accumulation of a (positive or negative respectively) metastable charge on the surface. The surface charge initially shows diffusive dynamics with a timescale of hours, but thereafter it is shown to be stable for months. The charged regions are found by Auger electron spectroscopy to have a different stoichiometry from the surrounding material. A part from fundamental implications for the heterostructure device construction, such surface charge manipulation could lead to AFM nanopatterning of superconducting nanoscale device and applications memories.
COBISS.SI-ID: 899242
A 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.
COBISS.SI-ID: 900522
In this article, the 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.
COBISS.SI-ID: 1206879
In 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.
COBISS.SI-ID: 904106