Effect of Surface Hardening Technique and Case Depth on Rolling Contact Fatigue Behavior of Alloy Steels

Abstract

Surface hardening techniques are widely used to improve the rolling contact fatigue (RCF) resistance of materials. This study investigated the RCF resistance of hardened, ground steel rods made from three different aircraft-quality alloy steels (AISI 8620, 9310, and 4140) and hardened using different techniques (atmosphere carburizing, vacuum carburizing, and induction hardening) at different case depths. The RCF life of the rods was determined using a three ball-on-rod rolling contact fatigue test machine. After testing, the microstructures of the rods were examined using metallographic techniques. The stress distributions and plastic deformation zones for the specimens under RCF were calculated using an elastoplastic model for plastically graded materials. Relationships between surface hardness, case depth, and RCF life were investigated. The longest lives were observed for the vacuum-carburized AISI 9310 specimens, and the shortest lives were observed for the induction-hardened AISI 4140 specimens. It is concluded that the most important factors in determining the RCF lives of high-cleanliness surface-hardened alloy steels are (1) the hardness in the region of highest octahedral shear stress (in this case, ∼0.13 mm beneath the surface) and (2) the depth of high hardness (>613 HV), which determines the plastic deformation zone size.

Modeling and Analysis of Effective Case Depth on Meshing Strength of Internal Gear Transmissions

“…The stress and displacement distribution of the carburized gear pair in any position can be achieved through transient analysis of the FEM models of the carburized gear pair using (1) to (19). The maximum stress can be obtained by reading the maximum contact stress on the surface of the tooth root of the carburized gear using (1). Furthermore, we calculated the maximum shear stress in the carburized layer and obtained the worst meshing point and corresponding meshing-gear number.…”

“…Carburizing and quenching heat treatment have been widely adopted to enhance gear strength and wear resistance. The use of a carburizing process in gear transmission systems is an important means of achieving a lightweight gear design because the carburized gear teeth usually acquire sufficient toughness, hardness, and wear resistance [1,2]. It is well known that the increase of carburizing depth can improve the strength of gears and prevent failure.…”

Fatigue Life Prediction for Gas Turbine Bearing Under 3D Elastoplastic Mixed Lubrication Condition

“…Oswald et al [9] incorporated the effects of residual and hoop stresses of rolling bearing fatigue life based on Zaretsky life equation were studied. Donglong Li [10], based on the experimental research of the rolling contact fatigue test was investigated by Xie et al [11] established a three-dimensional elastoplastic rolling contact model, and the experimental results show that the greater the hardness of the material at the position where maximum residual stress occurs, the longer the fatigue life. Chao Pu et al [12][13] analyzed the influence of cracks on elastoplastic lubrication performance of deep groove ball bearings, and solved the heavy load problem with semi analytical method, which greatly improved the calculation efficiency.…”

Contact Yield Initiation and Its Influence on Rolling Contact Fatigue of Case-Hardened Steels

“…Jackson and Green [31] improved the understanding of plasticity index and defined a closed-form solution for surface asperities in a Gaussian distribution, along with an alternative method to define a plasticity index. Xie et al [32] investigated the plastic deformation zones beneath the surface of AISI 8620, 9310 and 4140 steels subjected to the surface hardening under the cycle loading, and the relationships between surface hardness, case depth, and RCF life. Recently, Gupta and Zaretsky [33] presented a stress-fatigue life model based on the fundamental Lundberg-Palmgren life [34], indicating the dependence of contact fatigue on subsurface maximum shear stress and the stress volume.…”

“…The research aims to quantify the location of the first yield with respect to case depth and surface hardness and to determine the critical hardness profile that helps avoid contact yielding. The results are used to explain the rolling contact fatigue behaviors of several case-hardened steels reported in our previous work [32].…”