Improving the technology for manufacturing steel products with stress concentrators using surface resource-saving hardening methods: abstract of dissertation for an academic degree candidate of technical sciences: Specialty: 2.6.17. Materials Science/ Purtova Elena Viktorovna; Department of “Materials, technologies and quality” at the federal state autonomous educational institution of higher education “Naberezhnye Chelny institute (branch) of Kazan (Volga Region) federal university”