Carburized steel component and carburization process

A carburized steel component, comprising:

• a steel base including, by weight percent, from 0.18% to 0.23% carbon, 0% to 0.35% silicon, 0% to 4.0% nickel, 0% to 0.5% molybdenum, 0% to 0.06% niobium, and a remaining weight percent of manganese, chromium, and iron;
• and
• a carburized layer of above 0.35% by weight carbon from a surface of the carburized layer to a carburized layer depth, wherein the carburized layer depth is from 0.5 mm to 3.0 mm,
• wherein the carburized layer comprises a microstructure including martensite, retained austenite, carbide, and less than 2% by volume non-martensitic transformation products (NMTP), and wherein the carburized layer includes a prior austenite average grain size of 3.0-8.0 microns from the surface to a depth of at least 0.2 mm.

A carburized steel component, comprising:

• a steel base including, by weight percent, from 0.18% to 0.23% carbon, 0.5% to 1.30% manganese, 0% to 0.35% silicon, 0.2% to 2.0% chromium, 0% to 4.0% nickel, 0% to 0.5% molybdenum, 0% to 0.06% niobium, and a remaining weight percent of iron;
• and
• a carburized layer, wherein the carburized layer extends from a surface of the carburized layer to a depth from 0.5 mm to 3.0 mm,
• wherein the carburized layer comprises a microstructure including 70-90% by volume of martensite, retained austenite, at least 7% by volume of carbide, and less than 2% by volume non-martensitic transformation products (NMTP),
• wherein the carburized layer further includes a carbide area fraction over 10% from the surface of the carburized layer to a depth of 300 microns.

A method of manufacturing a carburized steel component, the method comprising:

• a steel base including, by weight percent, from 0.18% to 0.23% carbon, 0% to 0.35% silicon, 0% to 4.0% nickel, 0% to 0.5% molybdenum, 0% to 0.06% niobium, and a remaining weight percent of manganese, chromium, and iron;
• and
• shaping a steel material to form a component;
• carburizing the steel component in the temperature range of 900° C. to 1000° C. until forming a carburized layer;
• cooling the carburized component to below 100° C.;
• reheating the cooled carburized component at a temperature from 760° C. to 830° C.;
• and
• re-cooling the carburized steel component via quenching, wherein the carburized steel component is reheated and re-cooled so that the carburized layer includes a mean grain diameter of 5 microns to 6 microns.