高氮不锈轴承钢中的碳氮化物对力学性能的影响

Effect of the Carbon Nitrogen Compounds on the Mechanical Properties of High Nitrogen Stainless Bearing Steel

440C等高碳马氏体轴承钢中由于存在大量粗大的共晶碳化物,降低其耐蚀性和疲劳性能,影响了其广泛应用。40Cr15Mo2VN作为一种新型高氮不锈轴承钢,通过降低碳含量,增加氮含量和微合金化来改善其性能。氮的加入一方面析出细小弥散的氮化物,强化了基体;另一方面改善了钢中析出的碳化物的形态、尺寸和分布,使其由原来的带状和网状连续分布变为近圆形颗粒,最大碳化物尺寸由原来的70μm以上减小到小于18μm,弥散分布,从而使Rm达到2 000MPa以上,ReL达到1 700MPa以上,有些超过1 800MPa,表面硬度≥58.5(HRC),U型缺口冲击功保持在8J以上,并具有优异的耐蚀性和疲劳性能,满足轴承钢的服役要求。

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. 40Cr15Mo2VN 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 ttm. 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 Rm of over 2 000 MPa; RaL of above 1 700 MPa, some can reach over 1 800 MPa HRC 58.5 and impact work （U type gap） of over 8J. Meantime, it had excellent corrosion resistance and fatigue performance, and met the requirements of the bearing steel service.