Carbonitrided bearing component
A core portion of the carbonitrided bearing component includes a chemical composition consisting of, in mass %, C: 0.15 to 0.45%, Si: 0.50% or less, Mn: 0.20 to 0.60%, P: 0.015% or less, S: 0.005% or less, Cr 0.80 to 1.50%, Mo: 0.17 to 0.30%, V: 0.24 to 0.40%, Al: 0.005 to 0.100%, N: 0.0300% or less, O: 0.0015% or less, and the balance being Fe and impurities, and satisfying Formula (1) to Formula (4) described in the embodiment of the present specification. A concentration of C of its surface is, in mass %, 0.70 to 1.20%, a concentration of N of the surface is, in mass %, 0.15 to 0.60%, a Rockwell C-scale hardness HRC of the surface is 58 to 65, and in the core portion, an area ratio of an area of coarse V-based precipitates to a total area of V-based precipitates is 15.0% or less.
1. A carbonitrided bearing component comprising:
a carbonitrided layer formed in an outer layer of the carbonitrided bearing component; and
a core portion inner than the carbonitrided layer, wherein
the core portion has a chemical composition consisting of, in mass %:
C: 0.15 to 0.45%,
Si: 0.50% or less,
Mn: 0.20 to 0.60%,
P: 0.015% or less,
S: 0.005% or less,
Cr: 0.80 to 1.50%,
Mo: 0.17 to 0.30%,
V: 0.24 to 0.40%,
Al: 0.005 to 0.100%,
N: 0.0300% or less,
O: 0.0015% or less,
Cu: 0 to 0.20%,
Ni: 0 to 0.20%,
B: 0 to 0.0050%,
Nb: 0 to 0.100%,
Ti: 0 to 0.100%,
Ca: 0 to 0.0010%, and
the balance being Fe and impurities, and
satisfying Formula (1) to Formula (4), wherein
a concentration of C of a surface of the carbonitrided bearing component is, in mass %, 0.70 to 1.20%,
a concentration of N of the surface of the carbonitrided bearing component is, in mass %, 0.15 to 0.60%,
a Rockwell hardness C scale HRC of the surface of the carbonitrided bearing component is 58.0 to 65.0, and
in the core portion, when a precipitate containing V is defined as a V-based precipitate, and the V-based precipitate having an equivalent circle diameter of more than 150 nm is defined as a coarse V-based precipitate, an area ratio of an area of coarse V-based precipitates to a total area of V-based precipitates is 15.0% or less:
1.50<0.4Cr+0.4Mo+4.5V<2.45 (1)
2.20<2.7C+0.4Si+Mn+0.45Ni+0.8Cr+Mo+V<2.80 (2)
Mo/V≥0.58 (3)
(Mo+V+Cr)/(Mn+20P)≥2.40 (4)
where each symbol of an element in Formula (1) to Formula (4) is to be substituted by a content of a corresponding element (mass %).
2. The carbonitrided bearing component according to claim 1 , wherein
the chemical composition of the core portion contains one or more types of element selected from the group consisting of:
Cu: 0.01 to 0.20%,
Ni: 0.01 to 0.20%,
B: 0.0001 to 0.0050%,
Nb: 0.005 to 0.100%, and
Ti: 0.005 to 0.100%.
3. The carbonitrided bearing component according to claim 2 , wherein
the chemical composition of the core portion contains
Ca: 0.0001 to 0.0010%.
4. The carbonitrided bearing component according to claim 1 , wherein
the chemical composition of the core portion contains
Ca: 0.0001 to 0.0010%.
5. The carbonitrided bearing component according to claim 1 , wherein
2.20<2.7C+0.4Si+Mn+0.45Ni+0.8Cr+Mo+V<2.78 (2).
6. The carbonitrided bearing component according to claim 1 , wherein
(Mo+V+Cr)/(Mn+20P)≥2.47 (4).