New Technologies of Grain Boundary Engineering of Materials for Improving the Corrosion Resistance of High Alloy Stainless Steel Pipes

Problem. Pipes made of highly alloyed corrosion-resistant steels are widely used in corrosive-aggressive environments in priority industries. In connection with the increasing severity of their operating conditions, increased requirements for resistance to intercrystalline, pitting corrosion, corrosion cracking, and sulfide corrosion cracking under stress become the most important in accordance with the requirements of foreign and international standards. Previous studies have shown that currently operating technologies for the production of pipes do not meet the modern, comprehensive requirements for quality characteristics. To solve this problem, it is necessary to apply new progressive scientific and technological methods. Goal. The purpose of the work is to increase the corrosion resistance and operational reliability of pipes made of highly alloyed austenitic and ferritic-austenitic steels by improving their structure during deformation and temperature treatments according to the principle of grain boundary engineering of materials. Methodology. To achieve the goal, the latest scientific achievements and technologies for improving the structure and increasing the corrosion resistance of rolled products made of high-alloy steel were analyzed. When conducting experimental studies, modern methods were used and methods of metal structure research and complex corrosion tests for resistance to local types of corrosion to which corrosionresistant steels are subjected in operating conditions were developed. The results. The latest technologies for the production of pipes from austenitic chromenickel and ferritic-austenitic chrome-nickelmolybdenum steels, based on the principle of grain boundary construction of polycrystalline materials, have been developed. They ensure obtaining a structure of pipes with an increased content of special low-energy grain boundaries in the theory of coinciding site lattices (CSL) and high resistance against local types of corrosion in accordance with new industry requirements. Originality. For the first time, special low-energy grain boundaries in the ferritic component and interphase boundaries with reduced surface energy in highly alloyed ferriticaustenitic steels were found. The leading role of special boundaries in increasing resistance to local types of corrosion that originate at grain boundaries is shown. Practical value. The results of the work were implemented in the production at Centravis Production Ukraine PJSC, which contributed to the improvement of the quality and competitiveness of products