High Temperature Corrosion

The following sections are included:

• Foreword
• Contents
• Overview
• Addresses of Corresponding Authors
• Biography

Material degradation at high temperatures takes place due to loss in mechanical properties with increase in temperature as well as due to the chemical interaction of metal with the environment. This chemical interaction is further sub-divided into oxidation, sulfidation, and hot corrosion. While oxidation leads to the formation of oxide, which can be deleterious if the oxide is fast growing and spalls extensively, however, if the scale formed is adherent, thin and slow growing, it provides protection to the base metal or alloy. Sulfidation is a much severe degradation process and several times faster than the oxidation. In many industrial environments, it is a mixed gas environment, leading to oxidation and sulfidation simultaneously. Hot corrosion is another degradation mechanism which is even more severe than the oxidation and the sulfidation. Here, oxidation/sulfidation occurs in the presence of a molten salt on the surface of the substrate. Related issues, such as role of defect structure, active element effect and stress generation, during oxide growth process, have also been discussed. Finally, a guide to material selection for high temperature application is presented.

The following sections are included:

• Introduction
• Creep
  • Corrosion and Creep
    • Positive effect of corrosion on creep
    • Negative effect of corrosion on creep
• Fatigue
  • HTF in Corrosive Environments
• Summary
• References

The following sections are included:

• Introduction
• Heat-Resistant Ferritic Steel
  • Alloy Design
  • Materials for Fossil Power Plant
  • Advanced Ferritic Steels
• Heat-Resistant Austenitic Steels
  • Alloy Design
  • Materials for Heat Exchanger and Boiler Tubes
  • Advanced Austenite, Fe–Ni, and Ni-based Alloys
• Ni-based Superalloys
  • Progress for Gas Turbine and Jet Engine
  • Composition and Crystal Structure
  • Mechanical Properties
• ODS Alloys
  • Fe-based ODS Steels
  • Ni-based ODS Alloys
• Summary for Temperature Capability
• References

The following sections are included:

• Introduction
• High Temperature Corrosion
• High Temperature Materials
• Some Typical Applications and Case Stories for High Temperature Materials
  • Petrochemical Plants
  • Ethylene Furnace Tubes
  • Lance Tubes in Steel Plant Blast Furnaces
  • Muffle Tubes in Heat Treatment Furnaces
  • Recuperator Tubes
• References

The following sections are included:

• Introduction
• Indian Scenario of Power Generation
• Types of Thermal Power Plants
  • Steam Boiler
  • Combustion Turbines
  • Combined Cycle
• Corrosion in Coal-Based Power Plants
  • Fireside Corrosion
    • Mechanism of molten salt or slag-related attack
• Fireside Erosion Problems
• Steamside Corrosion Problems
• Waterside Corrosion Problems
• Corrosion Control Methodologies for Power Plants
• Corrosion Protection Methods
  • Selection of Materials
• Summary
• References

The following sections are included:

• Introduction
• High Temperature Alloy Development
• Oxidation and Hot-Corrosion Resistance
• Failure Modes of a Turbine Blade
• Protection Technology of Turbine Blades and Vanes
• Future Trends
• References

Coatings that survive high temperature and provide compatibility with the environment as well as with the substrates play an important role in different industrial sectors such as manufacturing, energy sector, transportation, waste-remediation, nuclear, space etc. Based on the type of application, the coatings have been developed so as to combat corrosion, wear, heat transfer, mass transport of unwanted species from environment into the bulk etc. Ceramics, intermetallics, cermets etc., have been known to possess high temperature stability. Additionally, some coatings demand functional properties along with high temperature stability, such as in solar applications. The present chapter discusses about different high temperature applications specific to energy sector such as thermal power, fusion reactors, fission reactors, solar power plants where coatings play a critical role and the factors affecting their selection and processing step have been elaborated.

The following sections are included:

• Introduction
• Sputtering and Ion–Solid Interactions
• FIB Secondary Electron and Secondary Ion Imaging
• FIB–SIMS
• References

Role of nanocrystalline and ultra-fine grained metals/alloys in improving the high temperature corrosion/oxidation characteristics is presented. The primary content of the chapter is an elaborate description of the authors' recent hypothesis and its experimental validation that a nanostructure can bring about dramatic improvements in the oxidation resistance of low chromium iron-chromium alloys at moderately high temperatures. A nanocrystalline Fe-10wt.%Cr alloy was found to undergo oxidation at a rate that was an order of magnitude lower than its microcrystalline counterpart. Importantly, the oxidation resistance of nanocrystalline Fe-10wt.%Cr alloy was comparable with that of the common corrosion-resistant microcrystalline stainless steels (that have 18–20 wt.% chromium). However, the chapter also provides a brief description of the difficulties in the processing of nanocrystalline iron-chromium ferritic alloys as well as the success in circumventing these difficulties. To set the scene on the oxidation resistance of nanocrystalline alloys, the chapter presents a summary of the recently reported roles of nanocrystalline structure in oxidation resistance of a few other chromia and alumina forming systems. The chapter also includes a brief description on the mechanism of oxidation resistance of alloys simultaneously having with both nano- and microcrystalline structure (i.e., bimodal structure).

The following sections are included:

• Introduction
• The Mechanisms of the Reactive Element Effect
  • General Remarks
  • Effect of REs on Alumina Scale Microstructure and Transport Processes
  • Effect of REs on Oxide Scale Adherence
• Selected Aspects of REs Use in Practical Applications
  • General Remarks
  • Chromia Forming Oxide Dispersion Strengthened (ODS) and Wrought Alloys
  • Reactive Element Reservoir in FeCrAl-Alloys
  • Interaction of REs with C and N Impurities
  • RE-Effects in Alumina Forming Coatings
• Conclusions
• References

The following sections is included:

• Index