DECHEMA

About: DECHEMA is a nonprofit organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Corrosion & Oxide. The organization has 756 authors who have published 1307 publications receiving 25693 citations.

Das Korrosionsverhalten von Hartmetall‐Verbundwerkstoffen in chloridhaltigen wäßrigen Lösungen

Abstract: Zur Klarung der Korrosionsvorgange an Nickel-und Cobalt-gebundenem Wolframcarbid werden zwei Apparaturen nach dem Prinzip der rotierenden Scheibe eingesetzt, die den Einflus der Korrosionsparameter Chloridkonzentration, Temperature und Stromungsgeschwindigkeit erfassen. Es wird gezeigt, das durch die Kombination des kathodisch wirksamen WC mit der anodisch wenig stabilen Metallmatrix eine Sauerstoffkorrosion auftritt, fur die der Begriff der inneren Kontaktkorrosion eingefuhrt wird. Diese innere Kontaktkorrosion last sich durch ein Porenmodell beschreiben, das am Grund der Pore aus dem metallischen Binder, an der Wand hauptsachlich aus WC und in der Pore aus Korrosionsprodukten besteht. Eine Abschatzung der Korrosionsraten auf der Basis dieses Modells ergibt Korrosionsraten in der Grosenordnung der Werte aus der Praxis.

Growth Stresses in the Oxide Scales on TiAl Alloys at 800 and 900°C

Abstract: In the oxidation of TiAl alloys, the role of scale-growth stresses formed during oxidation has, thus far, been unknown. In the present paper the oxide-growth stresses were investigated by the deflection-test method in monofacial oxidation (DTMO) accompanied by acoustic-emission measurements. On unmodified surfaces the growth stresses are compressive and reach levels of around −100 MPa. At the same time, significant acoustic emission occurs indicating that even under isothermal conditions, stresses are relieved by a scale-cracking mechanism. For oxide scales on TiAl surfaces, which had been ion implanted with chlorine before oxidation, a very thin protective alumina layer is formed which, however, develops growth stresses in the range of several GPa, accompanied by intensive acoustic emission. In all stress–time curves, a dynamic situation is observed. This consists of phases of stress relief by scale microcracking and phases of stresses increase due to crack healing and further oxide growth. As a result, the level of stress as a function of oxidation time, is characterized by an oscillating course.