稀土对GCr15轴承钢夹杂物和疲劳性能的影响

Effect of rare earth on inclusions and fatigue properties of GCr15 bearing steel

为深入探究稀土(La/Ce)对GCr15轴承钢中夹杂物和疲劳性能的影响,采取聚焦离子束技术(FIB)、X射线能谱分析(EDS)、扫描电子显微镜(SEM)、夹杂物无损提取、纳米压痕试验等多种不同的分析测试手段对不同稀土含量的GCr15轴承钢中夹杂物进行了剖析和表征,并通过超高周疲劳试验,对比分析了加入稀土(La/Ce)前后GCr15轴承钢疲劳性能的变化。结果表明,稀土优先与钢中的O、S元素反应,形成稀土氧硫化物,其可以单独存在或与其他夹杂物共生,呈细小颗粒弥散分布在钢中,尺寸在10μm以下;稀土氧硫化物还可将其他硬质夹杂物如镁铝尖晶石等包裹,改变了夹杂物形貌的不规则性。此外,稀土夹杂物与基体的等效弹性模量和硬度值更为接近,在载荷下变形差异缩小,与基体的协调性增强。稀土变质改性夹杂物改善了轴承钢的抗疲劳性能,在10^(7)周次、50%的失效概率条件下,加稀土的GCr15-RE轴承钢疲劳极限比未加稀土的GCr15轴承钢高125 MPa,具有更高的抗疲劳可靠性。以上结论为稀土对轴承钢夹杂物的改性研究及GCr15轴承钢性能优化提供了理论基础。

To investigate the effect of rare earth(La/Ce)on inclusions and fatigue properties of GCr15 bearing steel,the inclusions in bearing steels with different rare earth contents were analyzed and characterized by means of focused ion beam(FIB),energy dispersive X-ray spectroscopy(EDS),scanning electron microscope(SEM),non-destructive extraction and nano-indentation tests.The change of fatigue property for GCr15 bearing steel before and after adding rare earth(La/Ce)was analyzed by ultra high cycle fatigue test.The results show that rare earth elements react preferentially with O and S elements in steel to form rare earth oxysulfide inclusions,which can exist alone or coexist with other inclusions and distribute in steel as fine particles with their size less than 10μm.Other hard inclusions,such as magnesia-alumina spinel,can also be coated by rare earth oxysulfide,which changes the irregular morphology of the inclusions.In addition,the equivalent elastic modulus and hardness between rare earth inclusion and matrix are closer,so their deformation difference is reduced under loading and the compatibility is enhanced.The anti-fatigue property of bearing steel is improved by modifying inclusion with rare earth addition.Under the condition of 50%failure probability for 107 cycles,the fatigue limit of GCr15-RE bearing steel with rare earth addition is 125 MPa higher than that of GCr15 bearing steel without rare earth addition,and the fatigue reliability is higher.These conclusions provide a theoretical basis for the modification of inclusions in bearing steel by rare earth and the performance optimization of GCr15 bearing steel.