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38 MARCH 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 3 COATINGS & LININGS A A high-temperature powder process- ing cell experienced significant corro- sion at 1,100 °C within 30 days. To se- lect appropriate materials for service, trials were carried out on engineering alloys at 1,100 °C for 336 h. Two simu- lated environments were used; 10% carbon monoxide (CO)-1% carbon di- oxide (CO 2 )-89% argon and 90% car- bon monoxide (CO)-2.5% hydrogen gas (H 2 )-7.5% argon with samples cov- ered in titanium dioxide (TiO 2 ) powder. The samples' surface finish did not af- fect resistance to either environment, but more oxide powder adhered to ground surfaces. UNS N06625 and N06230 showed the greatest resis- tance to attack, while UNS N06600 showed moderate performance. Alu- minide diffusion coatings on UNS N06601, N06025, and N07214 were protective, but any coating defects yielded heavy localized corrosion. A key application of high-temperature corrosion testing is to aid intelligent mate- rials selection for use in challenging envi- ronments through acquisition and inter- pretation of data relating to corrosion modes and mechanisms, and methods of mitigating said corrosion. A case study is pre sent ed that inv olve s a propri et ar y industrial powder processing cell. The cell contains a complex environ- ment that reduces or partially reduces metal oxide powder. The materials of construction are in direct contact with the powder, including high-temperature nickel alloys, as well as moving components. Measurements indicate the gas composition changes along the length of the cell due to variations in temperature, reaction with the metal oxides, and interconversions in the gaseous envi- ronment. The temperature varies within the cell but approaches 1,100 °C in areas where the greatest corrosion and degradation were observed within one month's service. Thi s case study considers mat erial selection by investigating candidate alloys and coatings that might resist the proprie- tar y service environment and obtaining additional data on the corrosion mecha- nisms, corrosion rate, and any other related factors that may accelerate or retard in- service damage. Approach A series of Alloy 601 (UNS N06601) cou- pons were cut from the same rolled sheet and prepared with four different surface finishes. One set was ground to a 600-grit finish using silicon carbide (SiC) paper, another was polished to a 0.25-µm finish using diamond paste, and the third set was heat-treated for 12 h at 1,050 °C in air to form a protective oxide layer. The fourth set remained in the as-received condition. The polished coupon set was stored under CASE HISTORY High-Temperature Material Selection for a Powder Processing Environment Ro G e R B AR nett, TWI, Great Abington, Cambridgeshire, United Kingdom