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Title: Comparison of the cyclic oxidation behavior of beta-NiAl, beta-NiPtAl and gamma-gamma prime NiPtAl coatings on various superalloys

Abstract

Abstract The influence of exposure temperature on the cyclic oxidation behavior of simple and platinum aluminide coatings on various superalloy substrates was investigated. Coatings of -NiAl, -NiPtAl and - ' NiPtAl were tested and compared in dry oxygen at 1050 - 1150 aC. There was a clear influence of substrate sulfur content on the oxidation behavior of -NiAl coatings at all three temperatures. The impact of substrate impurities, especially S content, was significantly reduced for -NiPtAl coatings at all three temperatures. Simple { ' NiPtAl coatings showed excellent oxidation behavior up to 1100 aC on some alloys, but were more sensitive to substrate composition, especially Hf content, than were -NiPtAl coatings.

Authors:
 [1];  [1];  [2];  [1]
  1. ORNL
  2. Tennessee Technological University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Temperature Materials Laboratory
Sponsoring Org.:
FE USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
952210
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Surface and Coatings Technology; Journal Volume: 202; Journal Issue: 4-7
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; COATINGS; HEAT RESISTING ALLOYS; IMPURITIES; OXIDATION; OXYGEN; PLATINUM; SUBSTRATES; SULFUR CONTENT; coatings; oxidation; high temperature; bond coats; superalloys

Citation Formats

Haynes, James A, Pint, Bruce A, Zhang, Ying, and Wright, Ian G. Comparison of the cyclic oxidation behavior of beta-NiAl, beta-NiPtAl and gamma-gamma prime NiPtAl coatings on various superalloys. United States: N. p., 2007. Web. doi:10.1016/j.surfcoat.2007.06.039.
Haynes, James A, Pint, Bruce A, Zhang, Ying, & Wright, Ian G. Comparison of the cyclic oxidation behavior of beta-NiAl, beta-NiPtAl and gamma-gamma prime NiPtAl coatings on various superalloys. United States. doi:10.1016/j.surfcoat.2007.06.039.
Haynes, James A, Pint, Bruce A, Zhang, Ying, and Wright, Ian G. Mon . "Comparison of the cyclic oxidation behavior of beta-NiAl, beta-NiPtAl and gamma-gamma prime NiPtAl coatings on various superalloys". United States. doi:10.1016/j.surfcoat.2007.06.039.
@article{osti_952210,
title = {Comparison of the cyclic oxidation behavior of beta-NiAl, beta-NiPtAl and gamma-gamma prime NiPtAl coatings on various superalloys},
author = {Haynes, James A and Pint, Bruce A and Zhang, Ying and Wright, Ian G},
abstractNote = {Abstract The influence of exposure temperature on the cyclic oxidation behavior of simple and platinum aluminide coatings on various superalloy substrates was investigated. Coatings of -NiAl, -NiPtAl and - ' NiPtAl were tested and compared in dry oxygen at 1050 - 1150 aC. There was a clear influence of substrate sulfur content on the oxidation behavior of -NiAl coatings at all three temperatures. The impact of substrate impurities, especially S content, was significantly reduced for -NiPtAl coatings at all three temperatures. Simple { ' NiPtAl coatings showed excellent oxidation behavior up to 1100 aC on some alloys, but were more sensitive to substrate composition, especially Hf content, than were -NiPtAl coatings.},
doi = {10.1016/j.surfcoat.2007.06.039},
journal = {Surface and Coatings Technology},
number = 4-7,
volume = 202,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • No abstract prepared.
  • Here, the effects of superalloy composition and Pt content on the high-temperature oxidation behavior of γ–γ’ NiPtAl diffusion coatings were investigated over the temperature range of 1050–1150 °C. Simple NiPtAl diffusion coatings with 7 or 12 µm electroplated Pt thickness were evaluated in 1-h cycles in dry O 2 for up to 2500 cycles on four superalloys: directionally solidified (DS) alloy 142, 1st generation single-crystal (SX) alloy 1483, and 2nd generation SX alloys X4 and N5. Coatings on high-Hf alloy 142 experienced severe internal oxidation of Hf at all temperatures. Coatings on ~5 at.% Ti alloy 1483 were protective atmore » 1050 °C, but exhibited severe scale spallation at 1100 °C, with extensive formation of Ti- and Ni-rich oxides at the gas interface. Coatings with 7-µm Pt on X 4 were extremely protective at 1100 °C, but failed rapidly at 1150 °C, which also was associated with the formation of Ti-rich oxides. Increasing the coating Pt content on X 4 improved the 1150 °C oxidation behavior. Coatings on Ti-free N 5 showed the best performance at 1150 °C, especially with 12-µm Pt. Although γ–γ’ coatings can exhibit outstanding cyclic oxidation resistance with minimal Al depletion, they appear to be sensitive to substrate composition, as well as eventual Pt depletion due to interdiffusion.« less
  • In order to understand the beneficial effect of Pt on the adherence of thermally grown alumina scales, sessile drop experiments were performed to study the wetting of poly-crystalline alumina by nickel-aluminum alloys with or without platinum addition where the amount of Pt ranged from 2.4 to 10 at.%. Subsequent interfacial structure was evaluated using atomic force microscopy. Platinum addition enhances the wettability of NiAl alloys on alumina, reduces the oxide/alloy interface energy and increases the interfacial mass transport rates.
  • This study reports the effects of up to 4 at.% rhenium addition on the cyclic-oxidation behavior of {beta}-NiAl+{alpha}-Cr alloys having a base composition (in at.%) Ni-40Al-17Cr. Tests were conducted in still air at 1100 C for up to 250 1-hr cycles. The ternary alloy (without rhenium addition) exhibited poor cyclic-oxidation resistance, undergoing extensive scale spallation and internal oxidation. Additions of rhenium considerably improved the oxidation behavior, reducing the extent of both scale spallation and internal oxidation. These beneficial effects increased with increasing rhenium content. Rhenium additions improved cyclic-oxidation resistance by both decreasing the solubility of chromium in the {beta} phasemore » and causing the interdendritic {alpha}-Cr precipitates in the alloy microstructure to become more spheroidized and disconnected. These effects aided in preventing both interdendritic attack and the dissolution of the {alpha}-Cr precipitates from the subsurface region of the alloy. The maintenance of {alpha}-Cr precipitates at the alloy-scale interface decreased the extent of scale spallation by providing a lower coefficient of thermal-expansion (CTE) mismatch between the alloy and the Al{sub 2}O{sub 3}-rich scale.« less
  • The effect of 0.1 at.% Zr(0.2 wt. % Zr) on the cyclic oxidation of hipped ..beta..-NiAl was studied. Oxidation testing was performed in static air at 1100-1200/sup 0/C, using 1-hr exposure cycles for test times up to 3000 hr. The weight change versus time data were modeled with the COSP computer program to analyze and predict cyclic-oxidation behavior. Zr additions significantly change the nature of the scale-spalling process during cooling so that the oxide spalls near the oxide-air interface at a relatively low depth within the scale. Without Zr, the predominantly ..cap alpha..-Al/sub 2/O/sub 3/ scale tends to spall randomlymore » to bare metal at relatively high effective-scale-loss rates, particularly at 1150/sup 0/C and 1200/sup 0/C. This leads to higher rates of Al consumption for the Zr-free aluminide and much earlier depletion of al, leading to eventual breakaway (i.e., failure).« less