碳氮共渗M50NiL钢的磨削变质层微观组织和力学性能研究

Research of Microstructure and Mechanical Property of Grinding Modificative Layer of Carbonitriding M50NiL Steel

以碳氮共渗热处理后的M50NiL钢为研究对象,对不同粒度砂轮磨削后试样的表层微观形貌、表层组织结构、残余应力、显微硬度等进行了研究分析。研究结果表明,磨削后的试样表层变质层为非常细小的形变马氏体组织+奥氏体组织,为纳米晶区,晶面扭转现象明显,奥氏体含量与磨削热有直接关系,磨削后的表面变质层可分为3个部分,0~20μm的表层磨削热变质层、20~70μm的高硬度变质层及70~200μm的扩散变质层。为降低砂轮粒度对变质层组织性能的影响,可在磨削后去除适量的表面磨削变质层,但去除量不能超过磨削热变质层区的范围,以获得最佳的材料服役特性。

The surface modificative layer microstructure,residual stress and microhardness of carbonitriding M50NiL steel after different grinding parameters were studied.The results show that grinding surface modificative layer is very small deformation martensite and some austenite which is nanometer grain zone.The grain turning phenomenon is apparent.The content of austenite is affected by grinding heat of different grinding parameters.The grinding surface modificative layer may be divided into three parts,the outermost grinding heat affected layer about 0–20μm,the middle high hardness surface modificative layer about 20–70μm and the internal diffusion surface modificative layer about 70–200μm.In order to reduce the impact of different grinding parameters and improve the structure property of surface modificative layer,some grinding surface modificative layer may be removed but keep the maximum depth of not more than grinding heat affected layer and then the high mechanical properties of M50NiL steel are obtained.