Bearing part

A bearing part composed of a steel, the bearing part comprising a quench-hardened layer in a surface of the bearing part, wherein

• the quench-hardened layer includes a plurality of martensite crystal grains and a plurality of austenite crystal grains,
• each martensite crystal grain of the plurality of martensite crystal grains is determined such that a crystal orientation deviation between adjacent martensite crystal grains is more than or equal to 15°,
• a ratio of a total area of the plurality of martensite crystal grains in the quench-hardened layer is more than or equal to 70%,
• a ratio of a total area of the plurality of austenite crystal grains in the quench-hardened layer is less than or equal to 20%,
• the quench-hardened layer contains nitrogen,
• an average nitrogen concentration of the quench-hardened layer is more than equal to 0.15 mass % between the surface and a position at a distance of 10 μm from the surface of the bearing part,
• the plurality of martensite crystal grains are classified into a first group and a second group,
• all of crystal grain sizes belonging to the first group martensite is larger than all of crystal grain sizes belonging to the second group martensite,
• a value obtained by dividing a total area of the martensite crystal grains belonging to the first group by the total area of the plurality of martensite crystal grains is more than or equal to 0.5,
• a value obtained by dividing, by the total area of the plurality of martensite crystal grains, a total area of the martensite crystal grains belonging to the first group, except for a martensite crystal grain that has a minimum crystal grain size in the first group, is less than 0.5,
• an average grain size of the martensite crystal grains belonging to the first group is less than or equal to 0.97 μm, and
• an average aspect ratio of the martensite crystal grains belonging to the first group is less than or equal to 2.57.