Effect of the carbon nitrogen compounds on the mechanical properties of high nitrogen stainless bearing steel

The application of high carbon martensite bearing steel, like 440C, was limited, because the corrosion resistance and fatigue performance decreased due to the existence of lots of big eutectic carbide. 40Crl5Mo2VN with the decreased carbon, creased nitrogen and microalloy, which was a new type of high nitrogen stainless bearing steel, had the best match of strength and toughness. The addition of nitrogen could not only strengthen the matrix, but also improve the shape, the size and the distribution of the carbide. The shape of the carbide was improved from the original belt and mesh continuously distributed into a nearly round, and the maximum size was refined from over 70 μm to less than 18 μm, meanwhile the minimum size was less than 0. 1 μm. At the same time, nitrides were precipitated. These two aspects could make up for the decline of hardness that aroused by reducing carbon. The mechanical properties of the test steel could obtain R _m of over 2 000 MPa; R _eL of above 1700MPa, some can reach over 1800 MPa; HRC 58. 5 and impact work (U type gap) of over 8 J. Meantime, it had excellent corrosion resistance and fatigue performance, and met the requirements of the bearing steel service.