Curing damage in metallic materials by means of regenerative heat treatment

Abstract

Virtually any action on a metal (thermal, deformation, etc.) can lead to the development of damage, namely, the formation of microdiscontinuities (micropores and microcracks). Micropores and microcracks appear at the stage of technological preparation of the material and at the stage of its use. In addition, rather thorough structural transformations and changes in the stress-strain state in the bulk of the material may occur during use, which will change the kinetics of the formation of microdiscontinuities. It should be stressed that it is the formation of discontinuities that is directly responsible for failure of metallic materials. At present a great amount of experimental data has been accumulated that allows us to speak of the possibility of partial or complete elimination of microdefects using various kinds of treatment, especially heat treatment. Heat treatment at the stage of use or after it with the purpose of recovering the operating properties of parts and increasing their life is called regenerative heat treatment (RHT). In RHT a metallic material experiences three kinds of changes: curing of the damage, restoration of the structure, and changes in the stress-strain state. Most attention should be paid to the possibility of curing the damage, because the rate ofmore » development of damage determines the endurance of alloys. Various mechanisms for curing microdiscontinuities in RHT have been discussed in the literature.« less