High-temperature Corrosion of AlCrTiSiN Film in Ar-1%SO 2 Gas
AlCrSiN film with a composition of 29.1Al-17.1Cr-2.1Si-51.7N in at. % was deposited on a steel substrate by cathodic arc ion plating at a thickness of 1.8 μm. It consisted of nanocrystalline hcp-AlN and fcc-CrN, where a small amount of Si was dissolved. Corrosion tests were carried out at 800 ◦C for 5–200 h in Ar-1%SO2 gas. The major corrosion reaction was oxidation owing to the high oxygen affinity of Al and Cr in the film. The formed oxide scale consisted primarily of (Al,Cr)2O3, within which Fe, Si, and S were dissolved. Even after corrosion for 200 h, the thickness of the scale was about 0.7–1.2 μm, indicating that the film had good corrosion resistance in the SO2-containing atmosphere.
High temperature properties of CrAlN, CrAlSiN and AlCrSiN coatings – Structure and oxidation
CrAlN, CrAlSiN and AlCrSiN coatings were deposited by cathodic arc deposition technique from composite targets. Three targets were used: (i) Cr/Al ratio close to 1, (ii) Cr/Al ratio close to 1 with Si addition, and (iii) Cr/Al ratio close to 1/2 and Si addition. Nitrogen flow was kept constant during the depositions. The Cr/Al ratio of the films, measured by electron probe microanalysis (EPMA), was similar to that of the target and the silicon content was in the range 3–4 at.%. The coatings were deposited onto FeCrAl alloy and WC/Co mirror-polished substrates. To analyze the coating structure, X-ray photoelectron (XPS) and X-ray diffraction (XRD) analysis were used. The evolution of the coating structure up to 1000 °C was in situ measured in a XRD apparatus equipped with heating plate. The films oxidation behavior was characterized by thermogravimetric analysis (TGA) at two selected temperatures. The annealed coatings were analyzed by XRD and scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDX). CrAlSiN showed low oxidation resistance being partially oxidized at 800 °C. Moreover, the film exhibited low thermal stability, since the cubic nitride phases transformed to hexagonal nitrides at relatively low temperatures. CrAlN oxidation behavior was more promising; nevertheless, AlCrSiN showed excellent thermal stability with cubic nitrides observed even after heating to 1300 °C. The oxidation of this film at 900 and 1000 °C was negligible.
Using Infrared Thermography to Detect Moisture in Historic Masonry: A Case Study in Indiana
Nondestructive testing mapped water infiltration in the decoratively painted interior of a Masonic Temple in Muncie, Indiana.