DEVELOPMENT OF DAMAGE IN METALLIC MATERIALS

The service conditions for a metallic part are always individualistic. However, we can distinguish a set of general factors that accompany use and decrease the service life of the part and subsequently cause its failure. These factors are the degradation of the structure of the metallic part, the formation of internal stresses in it, and, as a consequence, the formation of microdiscontinuities such as microcracks and micropores. Continuous initiation and growth of these microdiscontinuities finally lead to failure of the material. In the articles presented below an attempt is made to generalize the results of foreign and their own investigations on the formation and curing of microdiscontinuities in metals and alloys formed in the production process and in service. The knowledge of the regularities in the formation of damage in metallic parts makes it possible to predict their service life, and the development of the methods for eliminating the damage makes it possible to increase it. In choosing the curing regimes the following factors have been taken into account: (1) the level of structural degradation and the continuity of the material; (2) the physical regularities of intensified curing of microcracks and micropores; (3) economic expediency. As a result, ways of treating metallic parts after service have been recommended that in some cases not only restore the properties of the initial material but even surpass them. In other words, it has become possible to include service in the technological cycle of additional improvement of a material. The work has been carried out at the Department of Metal Science of the Moscow State Academy of Instrument Engineering and Informatics, which had been led by M. E. Blanter for many years. Blanter was the initiator of this investigation and largely determined and directed the practical research. Further investigations carried out at the Department have demonstrated the advantages of this approach. The authors, who for the most part were disciples of M. E. Blanter, devote this set of works to the memory of their Teacher.