The Effects of Water Vapor on the Oxidation of Nickel-Base Superalloys and Coatings at Temperatures from 700�C to 1100�C

Abstract

The oxidation of superalloys that rely upon the development ofAl 2 O 3 or Cr 2 O 3 scales for oxidation resistance in air containing water vapor are compared at temperatures from 700°C to 1100°C. It is shown that water vapor affects the oxidation of such alloys in different ways. Water vapor adversely affects the selective oxidation of aluminum in the -Al 2 O 3 -formers, and also affects the adherence of these oxide scales. The major effect of water vapor on the chromia-formers is enhanced vaporization of Cr 2 O 3 . Aluminide coated superalloys are also examined in these cyclic oxidation tests, and it will be shown that water vapor caused spalling of the -Al 2 O 3 scales, but the effect is small for strongly adherent -Al 2 O 3 scales.

Oxidation of nickel-based single-crystal superalloys for industrial gas turbine applications

“…10c and d, for example, IN738LC lies above the critical isocontour at both 900°C and 1000°C, consistent with the micrographs reported in Refs. [33,34]. In addition, CMSX-4, Rene 0 N5 and PWA1484 lie below the critical isocontour, consistent with these alloys forming an Al 2 O 3 layer at both 900°C and 1000°C, and in agreement with the literature [10,[33][34][35].…”

“…In Data on the diagrams are taken from this study and also those reported in Refs. [7], [10] and [32][33][34][35][36]. Note the failure of Al 2 O 3 layer prediction in (a) and (b); in contrast, good agreement in (c) and (d), which make use of c c i for the calculation of the total effective valence.…”

“…[10]-for which the oxide morphologies have been reported in the literature [7,10,[32][33][34][35][36]; the testing conditions reported are summarized in Table 5. Note that there is some subjectivity involved in deciding whether any given alloy does indeed form a continuous layer of Al 2 O 3 , owing to the different practices used in the oxidation testing and the details reported.…”

In-Service Oxidation and Microstructural Evolution of a Nickel Superalloy in a Formula 1 Car Exhaust

“…However, the oxide layer itself on the inner surface is approximately 3-4 times thicker than that on the outer surface, signifying significantly accelerated corrosion when the surface is exposed to a dynamic, combustion productcontaminated environment and water vapour. Water vapour is likely to have been in contact with the inner exhaust surface, which is known to substantially increase the thickness of the chromia scale formed on nickel superalloys and steels [22,23].…”

On the Oxidation Resistance of Nickel-Based Superalloys

“…These have been done for the temperatures 900ºC and 1000ºC on the diagrams given in Fig 5. Thus the calculated line which is plotted passes through the point for SCA425+. Fig.5 also contains the calculated results of some well-known superalloyschemical compositions are given in [10] -for which the oxide morphologies have been reported in the literature [10][11][12][13][14][15]. Note that there is some subjectivity involved in deciding whether any given alloy does indeed form a continuous layer of Al 2 O 3 , owing to the different practices used in the oxidation testing and the details reported; however one can see that the alloys which perform adequately tend to lie below the calculated line, and those not performing well lie above it.…”