Comparison of Chromia Growth Kinetics in a Ni-based Superalloy, with and without Shot-peening

Abstract

Highlights • Two alloy surface treatments are compared. • The kinetics of a Ni-based superalloy are compared to pure chromia formation. • The enhancement is described in terms of Ti-doping of the surface chromia scale. • For the first time, a (Ta,Ti)O 2 phase, formed at the oxide metal interface, is identified.

The influence of stress on the oxidation of a Ni-based superalloy

“…Consistent with previous work [56], the surface oxide consisted of a titanium-enriched chromia layer, with an outer layer of discontinuous rutile, together with internally growing alumina intrusions within the alloy matrix, Figure 2 and Table 2. The internal intrusions are described…”

“…as intergranular, because formation predominantly occurs at the grain boundaries of small recrystallized grains with a diameter of approximately 1-3 µm, Figure 2, also described in [56].…”

An overview of the oxidation of Ni-based superalloys for turbine disc applications: surface condition, applied load and mechanical performance

“…IN718, RR1000, Udimet720, ME3, etc. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] using both isothermal and cyclic oxidation tests. In general, the oxide scale formed is usually duplex consisting of a dense chromia (Cr 2 O 3 ) layer and an outer layer of rutile (TiO 2 ) and a sub-surface internal oxidation zone (IOZ) of alumina (Al 2 O 3 ), often consisting of acicular intergranular penetrations [5,16,18].…”

Identifying heating rate dependent oxidation reactions on a nickel-based superalloy using synchrotron diffraction

“…At this stage in the oxidation process, the ease that oxidising elements diffuse through a growing surface oxide layer becomes a significant factor [10]. Investigations into the steady state oxidation of the nickel-based disc alloy of interest in this paper have been conducted [11][12][13][14][15][16][17] providing data for lifing models to predict, for instance, the onset of breakaway oxidation [18], or the loss of cross-section and mechanical integrity.…”

“…In a recent experiment [33] intended to examine the effect of elevated air pressure on the oxidation properties of a nickel-based superalloy, high-pressure tests resulted in the formation of a continuous external oxide layer of nickel chromite spinel (NiCr 2 O 4 ) rather than the more usual titanium doped chromia, (Ti, Cr) 2 O 3 , observed at atmospheric-pressure [11][12][13][14][15][16][17]. This result was unexpected and was unlikely to be a result of the difference in test pressure.…”