摘要:

In most industrial processes operating at elevated temperatures, protective oxide layers perform a vital duty in protecting the underlying metallic alloys from process gases. Coal-fired combined cycle power generation systems present a number of process conditions in which the properties of the protective oxide layers are particularly important. This paper discusses two of these particular conditions: (i)‘erosion/corrosion’of in-bed heat exchanger tubing and (ii) thermal cycling of hot gas path components. For both these situations, the desirable properties of protective scales are outlined. The behaviour of scales in practice are highlighted.

ISSN:0960-3409    

DOI:10.1080/09603409.1995.11689502

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The laws governing high temperature oxidation and de-alloying of high temperature nickel toasted alloys with aluminium content of up to 2% and their effect on the fatigue resistance at high temperatures are investigated. An experimental and calculation procedure to predict the elements distribution curves in the surface layer of blades, implemented by means of an algorithm and a program for solution of direct and inverse diffusion problems under the arbitrary law of temperature changing, with mobile boundary and selected limiting conditions has been developed.With the availability of sufficient data for a given alloy that characterize the diffusion and the influence of de-alloying on the longevity, the procedure allows a prediction of the remaining service life of the gas turbine blades.

ISSN:0960-3409    

DOI:10.1080/09603409.1995.11689503

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Creep rupture tests have been carried out on 1 Cr 1/2 Mo and 1/2Cr1/2Mo1/4V steels in the new (normalized and tempered) and in service exposed conditions. The results showed that the new materials were significantly stronger than the service exposed materials in tests of short duration, owing to the transient strengthening effects of carbon redistribution and carbide precipitation. With increasing test time the stress rupture strengths of the two conditions converged, as a stable microstructure was established in the new materials. The extrapolation of the new material data can lead to an underestimation of the long- term strength, continuing the steep/decrease in strength for the new material beyond the region in which experimental data are available. It is suggested that the stress rupture curve will in reality have a sigmoidal shape, as the results for new and service exposed materials must eventually come together.For the 1Cr1/2Mo steel, the creep damage developed in the longest tests depended on the condition. New material exhibited creep pore formation after relatively small creep strains of around 1% whereas the service exposed material exhibited no cavitation at creep strains of 5% after 10000 h testing. It was not possible in laboratory creep tests of 10 000 to 20 000 h duration to reproduce the creep damage typically found in components of this steel after prolonged service.

ISSN:0960-3409    

DOI:10.1080/09603409.1995.11689504

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

A study of the corrosion kinetics of a X20CrMoV 12–1 heat resistant stainless steel, at temperatures between 973 and 1273 K, has been carried out. The kinetic laws that rule the process and the corresponding constants for each temperature have been determined. The relationk = f(T)has also been established for the kinetic laws obtained. The results are justified by the microstructural changes observed during heat treatment.

ISSN:0960-3409    

DOI:10.1080/09603409.1995.11689505

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

An experimental and calculation procedure has been developed to determine the corrosion service life of the covering coatings that allows for (a) the relationship between corrosion rate and coating composition, (b) diffusion redistribution of elements in the coatings that takes place during a long stay at high temperatures, and (c) alternation of the oxide film A12O3under the layer of ceramics ZrO2+ Y2O3. The procedure makes it possible to calculate the coating longevity using an arbitrary operational model. The experimental part of the research involves the study of the coating elements distribution depending on time and temperature and the determination of general rules governing the growth of the oxide film A12O3and its critical value loading to fracture of ceramics at thermocyclic loading.

ISSN:0960-3409    

DOI:10.1080/09603409.1995.11689506

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

An important consideration in design is the determination of residual stresses developed during heat treatment of steel. By selecting an appropriate heat treatment technique, one can control the level of residual stresses in the components. Obviously beneficial residual stresses in the material increase the life of components. On the other hand, the unexpected failure of components that is later attributed to detrimental residual stresses is not uncommon.In this paper, residual stress distribution in a quenched long solid cylinder with temperature dependent properties is evaluated. Using three different speeds of cooling, the level of residual stresses for each speed was determined and compared with the others. From the stresses calculated, it was found that the tensile and tangential residual stresses are more sensitive to the speed of cooling than the radial one. For theoretical analysis a quasi-static uncoupled thermoelastoplastic analysis, based on incremental theory of plasticity, is developed and a numerical procedure for successive elastic solution approximation is formulated.

ISSN:0960-3409    

DOI:10.1080/09603409.1995.11689507

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor