Search Results for steam turbine blades

This article focuses on common failures of the components associated with the flow path of industrial gas turbines. Examples of steam turbine blade failures are also discussed, because these components share some similarities with gas turbine blading. Some of the analytical methods used in the laboratory portion of the failure investigation are mentioned in the failure examples. The topics covered are creep, localized overheating, thermal-mechanical fatigue, high-cycle fatigue, fretting wear, erosive wear, high-temperature oxidation, hot corrosion, liquid metal embrittlement, and manufacturing and repair deficiencies.

Liquid impingement erosion has been defined as progressive loss of original material from a solid surface due to continued exposure to impacts by liquid drops or jets. This article focuses on the core nature of erosion by liquid impingement, due to the greater appreciation of the distinctions between the different forms of erosion. It discusses steam turbine blade erosion, aircraft rain erosion, and rain erosion of wind turbine blades. The article describes the mechanisms of liquid impact erosion and time dependence of erosion rate. It reviews critical empirical observations regarding both impingement variables (velocity, impact angle, droplet size, and physical properties of liquids) and erosion resistance of materials, including the correlation between erosion resistance and mechanical properties and the effects of alloying elements and microstructure. The article also provides information on the ways to combat erosion.

The steam turbine is the simplest and most efficient engine for converting large amounts of heat energy into mechanical work. This article discusses the primary corrosion mechanisms such as corrosion fatigue, stress-corrosion cracking (SCC), pitting, corrosion, and erosion-corrosion, in steam turbines. It illustrates the various causes of the corrosiveness of the steam turbine environments through a Mollier diagram. The article describes the four parts of design disciplines that affect turbine corrosion, namely, mechanical design, heat transfer, flow and thermodynamics, and physical shape. It lists the ways to control the steam and surface chemistry, and design and material improvements to minimize turbine corrosion.

Erosion of solid surfaces can be brought about solely by liquids in two ways: from damage induced by formation and subsequent collapse of voids or cavities within the liquid, and from high-velocity impacts between a solid surface and liquid droplets. The former process is called cavitation erosion and the latter is liquid-droplet erosion. This article emphasizes on manifestations of damage and ways to minimize or repair these types of liquid impact damage, with illustrations.

This article describes the control of water chemistry in the steam cycle of a power plant for achieving corrosion control, deposition prevention, and higher cycle efficiency. It discusses the materials requirements of the components exposed to supercritical water in supercritical (SC) and ultrasupercritical (USC) power plants. These components include high-pressure steam piping and headers, superheater and reheater tubing, water wall tubing in the boiler, high-and intermediate-pressure rotors, rotating blades, and bolts in the turbine section. The article reviews the boiler alloys, used in SC and USC boilers, such as ferritic steels, austenitic steels, and nickel-base alloys. It provides information on the materials used in turbine applications such as ferritic rotor steels, turbine blade alloys, and bolting materials. The article explains various factors influencing steamside corrosion in SC power plants. It also deals with the role of overall efficiency in the USC power generation.

This article illustrates typical wear and friction issues encountered in gas and steam turbines and their consequences as well as commonly adopted materials solutions. It contains tables that present the summary of wear and friction related issues encountered in steam turbines and gas turbines. The article outlines the differences in the operating conditions and the nature of the components involved in gas and steam turbines. It discusses the constraints and applicable coating solutions for wear and friction issues, and concludes with a broad set of challenges that need to be addressed to improve performance and operability of gas and steam turbines.

Erosion of a solid surface can be brought about by liquid droplet impingement (LDI), which is defined as "progressive loss of original material from a solid surface due to continued exposure to erosion by liquid droplets." In this article, the emphasis is placed on the damage mechanism of LDI erosion under the influence of a liquid film and surface roughness and on the prediction of LDI erosion. The fundamentals of LDI and processes involved in initiation of erosion are also discussed.

Erosion occurs as the result of a number of different mechanisms, depending on the composition, size, and shape of the eroding particles; their velocity and angle of impact; and the composition of the surface being eroded. This article describes the erosion of ductile and brittle materials with the aid of models and equations. It presents three examples of erosive wear failures, namely, abrasive erosion, erosion-corrosion, and cavitation erosion.

The corrosion issues in the compressor, combustor and turbine sections of industrial gas turbines used in steam production generally depend on the quality of the fuel, air, and water used in the engine than on the specific industrial application. This article focuses on the forms of corrosion and their preventive measures in the compressor, combustor and turbine sections of a steam turbine. The compressor section mainly suffers from aqueous corrosion; while in case of the combustor and turbine sections, which are made of nickel-base superalloys, high-temperature environmental attack in the form of high-temperature oxidation and hot corrosion are predominant. The effect of high-temperature oxidation and hot corrosion on the mechanical properties of superalloys is also discussed.

This article focuses on the life assessment methods for elevated-temperature failure mechanisms and metallurgical instabilities that reduce life or cause loss of function or operating time of high-temperature components, namely, gas turbine blade, and power plant piping and tubing. The article discusses metallurgical instabilities of steel-based alloys and nickel-base superalloys. It provides information on several life assessment methods, namely, the life fraction rule, parameter-based assessments, the thermal-mechanical fatigue, coating evaluations, hardness testing, microstructural evaluations, the creep cavitation damage assessment, the oxide-scale-based life prediction, and high-temperature crack growth methods.

This article provides an overview of key abradable thermal spray coating systems based on predominant function and key design criteria. It describes two families of coatings which have evolved for use at higher temperature: flame (combustion)-sprayed abradable powders and atmospheric plasma-sprayed abradable powders. Three classic examples of flame spray abradables are nickel-graphite powders, NiCrAl-bentonite powders, and NiCrFeAl-boron nitride powders. The article provides information on various abradable coating testing procedures, namely, abradable incursion testing; aging, corrosion, thermal cycle and thermal shock testing; hardness testing; and erosion resistance testing.