Page 9 - Кулик В.В.

9

National Academy of Sciences of Ukraine, Lviv Polytechnic National University,

Ministry of Education and Science of Ukraine Lviv, 2019.

Thesis for the Doctor’s degree of Engineering Sciences in the specialty

05.02.01 – Materials Science (132 – Materials Science). – Karpenko Physico-

Mechanical Institute of the National Academy of Sciences of Ukraine, Lviv

Polytechnic National University, Ministry of Education and Science of Ukraine;

Karpenko Physico-Mechanical Institute of the National Academy of Sciences of

Ukraine, Lviv, 2019.

The thesis is directed to the development of requirements for steels of high-

strength railway wheels for simultaneous provision of high wear resistance and

resistance to the formation of defects (flats and gaps) on their tread surface, as well

as the substantiation of the chemical composition and structure and phase state of

new steels for manufacturing the wheels with improved lifetime.

On the basis of the researches presented in the thesis, from the standpoint of

structural mechanics of fatigue fracture, recommendations in the field of materials

science are formulated and substantiated, which provide a solution of the important

scientific and technical problem of increasing the reliability and durability of high-

strength railway wheels. A new concept for creating steels is proposed that

provides high resistance to wear and damage of the tread surface of the wheels.

Requirements for a complex of mechanical characteristics of such steels are

developed and the chemical composition of steel for railway wheels of a new

generation as well as the heat treatment mode for their repaired surfaces is

substantiated what is reflected in the conclusions.

To minimize the negative impact of operational factors on the resource

characteristics of wheel steels and the durability of high-strength railway wheels, a

new concept for creating wheel steels is proposed, according to which new steels

with a reduced carbon content are required to increase both the austenitizing

temperature (reduce the tendency to martensite transformations) and fatigue crack

growth resistance (K > 80 MPa∙√m) which determines the cracking on the tread
fc
surface, providing their high strength state with solid-solution and precipitation