THE EFFECT OF ANNEALING ON MICROSTRUCTURE OF STEEL NITRONIC 60
Nitronic 60 (UNS S21800) is a highly alloyed austenitic stainless steel with the increased content of manganese and silicon which has good mechanical and corrosion properties at high temperatures and loads. This paper presents the results of investigations of the influence of annealing process on the microstructure of steel Nitronic 60. Heat treatment consisted of annealing from 400 to 850 0 C for four hours followed by cooling in the water. The light and scanning electron microscope (with EDS analysis) were used for microstructure analysis. Analysis showed presence of sigma phase at higher temperatures. The sigma phase was precipited mainly at the austenite grain boundaries, δ/γ interface boundary and δ ferrite phase. Hardness testing showed increasing of hardness with precipitation of sigma phase.
Determination of the content of delta ferrite in austenitic stainless steel Nitronic 60
Microstructure of austenitic stainless steel Nitronic 60 is primarily monophasic ie. austenitic. However, the chemical composition can affect on precipitation of delta ferrite. The presence of delta ferrite decrease grain growth and increases strength properties of steel. It is known that, the delta ferrite has a very important role in welding of austenitic steels to prevent the occurrence of hot cracks. This paper presents the results of determining the content the delta ferrite in steel Nitronic 60 using the Schaeffler`s diagram, metallographic methods and method of magnetic induction. Analysis of results showed no significant differences in the content of delta ferrite in relation to deifferent methods of determining the delta ferrite.
Coated-wire electrodes containing polymer immobilized ionophores blended with poly(vinyl chloride).
Polymers containing covalently attached 18-crown-6 or 2.2.2 cryptand units were incorporated into plasticized PVC membranes and the composite membranes were examined as potassium ion sensor elements. Ionophores were linked to carboxy-PVC and to poly(acrylic acid) via amide linkages to an alkyl spacer unit. Coated-wire electrodes (CWEs) from the immobilized ionophores gave acceptable responses, but conventional ion-selective membrane electrodes (ISEs) prepared by solvent casting were inactive. Dip-cast membranes did give active ISEs. Potassium electrode performance was independent of the loading of the ionophore within the acrylate support polymer, but depended upon the spacer length. Ion selectivity varied with the ionophore loading within the support polymer. Selectivity is a composite of the ionophore selectivity and ion-exchange interactions with the acrylate backbone, giving selectivities akin to carboxylate substituted crown ethers, notably enhanced monovalent/divalent ion discrimination relative to the ionophore in solution. Polymer immobilization extended the lifetime of active electrodes.