Formation of aluminide coatings on Fe-based alloys by chemical vapor deposition

Zhang, Ying; Pint, Bruce A.; Cooley, Kevin M.; Haynes, J. Allen

doi:10.1016/j.surfcoat.2008.01.023

Cited by 54 publications

(31 citation statements)

References 40 publications

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“…13,[16][17][18][19][20][21][22][23] This information could then be used to justify the implementation and improve the durability of these coatings. Some of the initial concerns about these coatings were the coefficient of thermal expansion (CTE) difference between the aluminide phases (e.g.…”

Section: Introductionmentioning

confidence: 99%

Performance of Al‐rich oxidation resistant coatings for Fe‐base alloys

Pint

Zhang

2010

Materials & Corrosion

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This multi-layer program has examined the oxidation resistance of Al-rich coatings made by chemical vapor deposition and pack cementation on ferritic-martensitic (e.g. T91, Fe-9Cr-1Mo) and austenitic (Type 304L, Fe-18Cr-8Ni) substrates at 650°-800°C. The main goal of this work was to demonstrate the potential benefits and problems with alumina-forming coatings. To evaluate their performance, oxidation exposures were conducted in a humid air environment where the uncoated substrates experience rapid oxidation, similar to steam. Exposure temperatures were increased to accelerate failure by oxidation and interdiffusion of Al into the substrate. The final results focused on thinner coatings with less Al and a ferritic Fe(Al) structure which have a lower thermal expansion than intermetallic phases. To improve the previously developed coating lifetime model, a final series of exposures were conducted to determine the effect of substrate composition (e.g. Cr content using Fe-12Cr and Fe-9Cr-2W substrates) and exposure temperature on the critical Al content for coating failure. For the coated Fe-(9-12)Cr specimens, there was little effect of Cr on lifetime at 800°C. At 700° and 800°C, thin coated austenitic specimens (304L and 316) continue to be protective at up to double the lifetime of a similar coating on T91. This increase could be attributed to the higher Cr content or the slower interdiffusion in austenitic substrates which is illustrated with electron microprobe measurements from thicker coatings stopped after 10-20 kh.

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Section: Introductionmentioning

confidence: 99%

Performance of Al‐rich oxidation resistant coatings for Fe‐base alloys

Pint

Zhang

2010

Materials & Corrosion

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“…up to *19 at.% or 10 wt.%) alloys which are being investigated as compositions for weld-overlay coatings for fossil energy systems [3][4][5]. Similar compositions develop when a short-duration, Al vapor deposition process is used on martensitic steels [6]. Lower-Al-content ferritic coatings do not have a large coefficient of thermal expansion (CTE) which causes cracking in intermetallic (i.e.…”

Section: Introductionmentioning

confidence: 99%

Internal Oxidation–Nitridation of Ferritic Fe(Al) Alloys in Air

2008

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Exposure of undoped Fe(Al) and Fe(Al)+Cr ferritic alloys in laboratory air at 900-1,000°C resulted in significant internal attack after 5,000 h, including oxides and underlying nitrides. In the most severely attacked alloys, kinetics based on mass gain and maximum penetration depth were linear; also, the deepest penetrations were a significant fraction of the specimen thickness, and were thicknessdependent. Little internal attack was observed at 700-800°C where these compositions may be used as coatings. The extent of internal attack did not decrease with increasing Al or Cr content which may indicate that rather than classical internal oxidation this attack is related to the permeation of N through a defective external scale. No internal attack was observed in alloys doped with Y, Zr, Hf or Ti where the substrate-alumina scale interface was flatter.

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“…Consequently, the Fe 2 Al 5 coating was formed by inward diffusion of Al, which is typical for the high Al activity pack process. [20,22,23] However, when the non-contact pack-specimen arrangement (Fig. 3b) with porous alumina paper or foam was used, a significant variation in the specimen's weight gain was noticed after aluminizing, and residues of alumina paper or foam were found attached to the specimen surface.…”

Section: Aluminide Coatings Formed At 650 °C Using Pure Al Masteralloysmentioning

confidence: 99%

“…The CVD thick coating fabricated at 1050 °C had a thickness of ~260 m, and the CVD thin coating formed at 900 °C was ~50 m thick. [22] The pack coating made at 1050 °C had a thickness slightly greater than the CVD thick coatings, ~ 250-300 m. [33] The detailed microstructures of these CVD and pack coatings were reported elsewhere. [22,33] Pack 1050˚C, Cr15Al [33] 300 34 5100 FeAl 650 CVD 1050˚C [22] 260 26 3380 FeAl 650 CVD 900˚C [22] 50 18 450 FeAl 650, 700 Figure 17 shows the mass change plots of coated and uncoated specimens cyclically exposed at 650 °C in air + 10% water vapor.…”

Section: 3mentioning

confidence: 99%

“…[22] The pack coating made at 1050 °C had a thickness slightly greater than the CVD thick coatings, ~ 250-300 m. [33] The detailed microstructures of these CVD and pack coatings were reported elsewhere. [22,33] Pack 1050˚C, Cr15Al [33] 300 34 5100 FeAl 650 CVD 1050˚C [22] 260 26 3380 FeAl 650 CVD 900˚C [22] 50 18 450 FeAl 650, 700 Figure 17 shows the mass change plots of coated and uncoated specimens cyclically exposed at 650 °C in air + 10% water vapor. When the uncoated T91 alloy was tested in dry air at this temperature, a very low mass gain was observed, < 0.1 mg/cm 2 after 5,000 h. [8] However, in the presence of 10% water vapor, the uncoated alloy underwent accelerated oxidation after an incubation period.…”

Section: 3mentioning

confidence: 99%

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A Novel Low-Temperature Fiffusion Aluminide Coating for Ultrasupercritical Coal-Fried Boiler Applications

Zhang¹

2009

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Formation of aluminide coatings on Fe-based alloys by chemical vapor deposition

Cited by 54 publications

References 40 publications

Performance of Al‐rich oxidation resistant coatings for Fe‐base alloys

Performance of Al‐rich oxidation resistant coatings for Fe‐base alloys

Internal Oxidation–Nitridation of Ferritic Fe(Al) Alloys in Air

A Novel Low-Temperature Fiffusion Aluminide Coating for Ultrasupercritical Coal-Fried Boiler Applications

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