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Structural Steels for Power Industry

#0957


Development of New Cracking Criteria for Structural Steels of Power Industry in Aquatic Media

Tech Area / Field

  • MAT-SYN/Materials Synthesis and Processing/Materials

Status
3 Approved without Funding

Registration date
16.04.1997

Leading Institute
AO Kompozit, Russia, Moscow reg., Korolev

Supporting institutes

  • A.N.Frumkin Institute of Physical Chemistry and Electrochemistry, Russia, Moscow

Project summary

Objectives

The aim of the project is to search and develop new approaches to prognostication and exclusion of cracking1 of components of" water and steam equipment for both thermal and nuclear power stations for a long-term service.

Technical Approach

Failures due to the cracking of components of water and steam equipment nowadays are connected with the sensitivity of steels and alloys to stress corrosion cracking (SCO) and/or hydrogen embrittlament (HE) in water media - both electrolytic and nonelectroiytic. In relation with nuclear reactors security and reliable operation of power stations' equipment it is proposed for structural steels of power industry to find new qualitative criteria of the cracking and methods of their determination which are meaningful in a broad temperature and pressure range. Tentatively, the methods must be much less expensive than direct tests.

Possibility of a successful fulfillment of the project is grounded on the application of the concept of essentially new details of the cracking mechanism when there is no domination either of an anodic dissolution or apparent HE. The main feature of the concept is the idea of substructural defects - carriers of materials' detriment. They are generated due to interaction of a metal with an environment. The carriers essentially participate in initiation and slow growth of cracks.

To solve the problems fulfillment of the following goals is required:


- study of structures of oxide films on structural steels of nuclear and thermal power equipment under conditions of occurrence and absence of the cracking;
- establishment of facts and laws of formation of substructural defects in chosen materials under the same or specialmodified conditions;
- study of an interconnection between the formation of oxide films and the generation of substructural defects with the effects of concomitant hydrogenation;
- determination of the meaning of established facts and laws for the mechanism of the cracking of chosen materials.

On this basis it will be possible to ground the new structure-related criteria of the sensitivity of these materials to the cracking1 -and to work up the methods of determination of these criteria.

Anticipated Results

Data will be obtained on relationship of structure -and chemical contents of oxide films, formed on steels of different grades in aquatic media, and the sensitivity of materials to the-cracking. Simultaneously data will be obtained on type and density of structural defects - carriers of the cracking -generated under the same conditions. On the ground of analyses and the generalization of acquired data the possibility will be established to forecast the cracking in systems material-medium at the given nature of the material and parameters of a medium using only the results of determination of the nature of oxide film formed under the given conditions, or adding information to this on type and, quantity of substructural defects generated simultaneously with the oxide film. On this background will be chosen the qualitative criteria of the cracking, supposedly, as meaningful as results of some direct tests.

On the basis of the techniques to be newly worked up during the course of this project and adopted and modernized known techniques used for the solution of the project tasks will be developed test methods of determination of the new structure-related criteria, of cracking in aquatic media (from cold solutions to subcritical water) of structural steels of power industry. These methods which are significantly time saving compared with direct ones, will be recommended for a broad application in industry including attestation of certain batches of steel before starting fabrication of the equipment. Thus, the reliability of the power equipment in operation will be increased.

The work on development of the new structure-related criteria must be done by highly skilled performers that will lead to creation of new working places for workers of the military-industrial complex. Essentially less expenditure of chemicals during indirect tests compared with direct ones will be beneficial for ecology.


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