A test flight was cut short after a fire warning came on indicating a problem with one of the four engines on an aircraft. A visual examination following the precautionary landing revealed several burned hoses, a melted bolt, and fuel leaking from the base of the main burner. The fuel nozzle was also damaged, and based on its microstructure, came very close to melting. Investigators determined that the burner was mounted backwards, facing the compressor rather than the turbine. They also recommended a redesign to prevent the fuel nozzle from being reversed.

This chapter examines the hot corrosion resistance of various nickel- and cobalt-base alloys in gas turbines susceptible to high-temperature (Type I) and low-temperature (Type II) hot corrosion. Type I hot corrosion is typically characterized by a thick, porous layer of oxides with the underlying alloy matrix depleted in chromium, followed (below) by internal chromium-rich sulfides. Type II hot corrosion is characterized by pitting with little or no internal attack underneath. As the chapter explains, chromium additions make alloys more resistant to all types of hot corrosion attacks.

This chapter discusses material-related problems associated with coal-fired burners. It explains how high temperatures affect heat-absorbing surfaces in furnace combustion areas and in the convection pass of superheaters and reheaters. It describes how low-NOx combustion technology, intended to reduce NOx emissions, accelerates tube wall wastage. It also covers circumferential cracking in furnace waterwalls, thermal fatigue cracking induced by waterlances and water cannons, superheater-reheater corrosion, and erosion in fluidized-bed boilers.