Hot Corrosion Behavior of a Cr-Modified Aluminide Coating on a Ni-Based Superalloy

doi:10.1007/s40195-014-0108-5

Abstract

Abstract:

A Cr-modified aluminide coating is prepared on a Ni-based superalloy using arc ion plating and subsequent pack cementation aluminizing. Hot corrosion behavior of the Cr-modified aluminide coating exposed to molten Na₂SO₄/K₂SO₄ (3:1) or Na₂SO₄/NaCl (3:1) salts at 900 °C in static air are evaluated as well as the aluminide coating. The results indicate that compared with the aluminide coating, the anti-corrosion properties of the Cr-modified aluminide coating in the both salts are improved, which should be attributed to the beneficial effect of the Cr in the coating. The corrosion mechanism of the Cr-modified aluminide coating, especially the role of Cr in the mixture salt corrosion, is discussed.

Key words: Arc ion plating, Pack cementation aluminizing, Superalloy, Cr-modified aluminide coating, Hot corrosion

Duoli Wu, Sumeng Jiang, Qixiang Fan, Jun Gong, Chao Sun. Hot Corrosion Behavior of a Cr-Modified Aluminide Coating on a Ni-Based Superalloy[J]. Acta Metallurgica Sinica (English Letters), 2014, 27(4): 627-634.

Figures/Tables 11

Table 1 Deposition parameters of Cr layer by AIP

Operation stage	Arc voltage (V)	Arc current (A)	Bias voltage (V)	Bias duty cycle (%)	Temperature(°C)
Bombardment cleaning	20–30	60–70	-800	30	50–100
Chromium target	20–30	60–70	-200	30	100–150

Table 2 The compositions of the two coatings (wt%)

Coating	Al	Ti	Cr	Co	Ni
Al–Cr coating	31.9	0.4	13.2	6.4	Bal.
aluminized coating	25.6	0.5	5.3	6.8	Bal.

Fig. 1 XRD patterns of the aluminized coating and the Al–Cr coating

Fig. 2 Cross-sectional BSE images of the two coatings: a Al–Cr coating; b aluminized coating

Fig. 3 Line scanning images on the cross-sections of the aluminized coating a, the Al–Cr coating b

Fig. 4 Corrosion kinetic curves of DSM11 substrate, aluminized coating, and Al–Cr coating in the mixed salts of Na2SO4/K2SO4a, Na2SO4/NaCl b at 900 °C

Fig. 5 XRD patterns of the DSM11 substrate, the aluminized coating and the Al–Cr coating after corrosion at 900 °C for 100 h in mixed salts of Na2SO4/K2SO4a, Na2SO4/NaCl b

Fig. 6 SEM images showing the surfaces of DSM11 substrate a, aluminized coating b, Al–Cr coating c after corrosion at 900 °C for 100 h in the salt of Na2SO4/K2SO4

Fig. 7 Cross-sectional BSE images of DSM11 substrate a, aluminized coating b, Al–Cr coating c after corrosion at 900 °C for 100 h in the salt of Na2SO4/K2SO4

Fig. 8 SEM images showing the surfaces of DSM11 substrate a, aluminized coating b, Al–Cr coating c after corrosion at 900 °C for 100 h in the salt of Na2SO4/NaCl

Fig. 9 Cross-sectional BSE images of DSM11 substrate a, aluminized coating b, Al–Cr coating c after corrosion at 900 °C for 100 h in the salt of Na2SO4/NaCl

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