Original Article

Mechanism analysis of rare earth Y on mechanical properties of GCr15 bearing steel

¹ School of Energy and Architectural Engineering, Shandong Huayu University of Technology, Dezhou, 253034, PR China
² Shandong Green Low-Carbon Intelligent Cooling and Heating Technology Characteristic Laboratory, Dezhou, 253034, PR China
³ School of Rare Earth Industry, Inner Mongolia University of Science and Technology, Baotou 014010, PR China

^* e-mail: 15075866003@163.com

Received: 18 June 2025
Accepted: 24 September 2025

Abstract

In this paper, the mechanism of the effect of rare earth Y on the mechanical properties of GCr15 bearing steel was investigated by Zeiss metallurgical microscope, scanning electron microscope and field emission electron microscope. The results show that the tensile and yield strengths of the test steel with 0.005%Y are increased by 70.8 MPa and 74.9 MPa respectively, the elongation is increased by 32.0%, and the impact toughness is increased by 38.4%, fatigue life doubled. The addition of rare earth Y makes the microstructure of the test steel more compact and uniform, and modifies Al₂O₃, MnS, Al₂O₃+MnS into Y₂O₂S, YS, YS+MnS, the size of inclusions is reduced from 4 μm to about 1 μm, and the shape is changed from irregular geometric polygon to ellipsoid. After adding 0.005% rare earth Y, dimples and white fibrous tissue area were formed on the tensile fracture surface, and the fracture mode changed from brittle fracture to ductile fracture. The number of dimples on the impact fracture surface increases, while the river-like area and tear ridges decrease. A large number of dimples appeared at the fatigue fracture surface, the granular bright facet (GBF) area around the inclusions basically disappeared, and a large number of secondary fracture zones were generated, and the fatigue fracture mode changed from grain boundary fracture to transgranular fracture. The above experimental phenomena can be used to explain the basic reason why rare earths improve the mechanical properties of bearing steel. The type of inclusions at the tensile and impact fracture was changed from Al₂O₃-MnS to Y₂O₂S, the inclusions at the fatigue fracture are YAlO₃, and the rare earth inclusions were not easy to deform, under the action of external forces, they enhance the synergistic deformation capacity with the steel matrix, delay the generation of microvoids and micro-cracks, and thereby improve mechanical properties.