VDM® Alloy 699 XA (2.4842/N06699)

VDM^® Alloy 699 XA (2.4842/N06699) is a nickel-chromium-aluminum alloy patented by VDM Metals that is characterized by excellent metal dusting resistance.

Metal Dusting

Metal dusting is closely related to carburization. The mechanisms of metal dusting have been extensively researched for about 50 years. To this day, not all mechanisms have been clarified. Metal Dusting stands for a complex form of high-temperature corrosion in which the attacks seem to occur randomly distributed over the surface of the material. These attacks take place locally in the form of troughs or holes. In the immediate vicinity of the troughs there are dust-like corrosion products in the form of a dark grey to black powder - hence the name "Metal Dusting". Metal Dusting occurs in a medium temperature range between 400°C and 800°C. The risk of metal dusting increases with very high carbon concentrations (activities) in the process gas or on the material surface. In addition to the pressure and flow velocity of the gases, time also plays a role. The incubation period, i.e. the time until the first material damage, increases with the alloy content of the elements nickel, chromium, aluminium and silicon. Recent material developments such as VDM^® Alloy 699 XA show a maximum extended incubation time with simultaneous limitation of the damage depth.

Effective control of metal dusting requires concerted action on both the material and process sides. The catalytically controlled decomposition of carbon compounds to elemental carbon plays a central role in the process. The blocking of this catalytic activity can take place both on the process side and on the material side. This effectively interrupts the reaction chain to metal dusting.