SUJ2 Steel Research Articles

Coupled FEM Simulation of Induction Heating Process in the Austenitization of a SUJ2 Steel Ring

Coupled FEM Simulation of Induction Heating Process in the Austenitization of a SUJ2 Steel Ring

Non-propagation Behavior of Small Crack in Bearing Steel SUJ2 under High Compressive Mean Stress

Non-propagation Behavior of Small Crack in Bearing Steel SUJ2 under High Compressive Mean Stress

Effects of Doping Elements on the Friction and Wear of SUJ2 Steel Sliding against Aluminum Alloys

Damage to mechanical components caused by wear is considered to be an important issue for mechanical engineers. For the purpose of wear resistance, it is necessary to improve the material properties of the mechanical elements. Furthermore, low friction plays an important role in saving energy. Hence, it is important to establish a key technology for wear resistance and low friction through appropriate materials science for related industries. In general, the tribological properties of aluminum alloys are very different from those of steels. Hence, aluminum alloys should be specially considered and clarified for their tribological properties before being applied industrially. This paper therefore aims to further investigate the effects of the content of doping elements on the friction and wear of the selected aluminum alloys. From the experimental results, it can be concluded that the higher the Si content, the smaller the friction coefficient, and the milder the variation. The higher the content of iron and copper, the more materials are removed, showing better machinability. Moreover, three frictional models and wear mechanisms that describe the effects of the content of doping elements on the friction and wear are proposed. The wear mechanisms change as the silicon content increases, from the junction growth to the wedge and the ploughing particles. As a result, better choices of aluminum alloys with regards to friction and wear can then be made. These results have great practical importance.

ショットピーニングを施した軸受鋼の異物混入潤滑下における転がり疲労挙動評価

In this study, the effect of shot peening on rolling contact fatigue life of bearing steel was investigated under contaminated lubrication. Shot peening was carried out on bearing steel SUJ2 specimens. Peened specimens were polished to remove the dimples generated by shot peening. The distribution of Vickers hardness and residual stress of the specimens were measured before and after the shot peening. The resistance to indentations was compared by examining the profile of the Vickers indentations. Then, rolling contact fatigue tests were carried out under contaminated lubrication. The material hardness was improved up to about 100 HV on the surface to a depth of 300 μm, and compressive residual stress was generated up to 1546 MPa at a depth of 25 μm due to the shot peening. In addition to the width and the depth of the Vickers indentation, the ridge height which causes the stress concentration around the indentation, was reduced by 17% by the shot peening. The rolling contact fatigue life associated with a 50% reliability (L50) was improved 62 % by the shot peening. However, the improvement of rolling contact fatigue life associated with a 90% reliability (L10) was only 26 % because of the increase in dispersion of the fatigue lives due to surface cracks created by the shot peening. Based on the present result, the increase of surface hardness and generating the large compressive residual stress near the surface by shot peening was found to be effective in increasing the rolling contact fatigue life in contaminated lubrication.

Effect of Repeated Quenching on Rolling Contact Fatigue Properties of JIS SUJ2 Bearing Steel

One important method to improve the material properties is refinement of the prior austenite grain size. Repeated quenching is used as a grain refinement method. In the present work, samples of SUJ2 steel were furnace quenched once and thrice in order to investigate the effect of repeated quenching on rolling contact fatigue (RCF) strength. After the RCF tests, maicrostructure observations, Vickers hardness and retained austenite measurements, RCF life evaluation using the Weibull distribution were carried out. It was found that the dispersion of the life population was reduced by repeatedly quenching.

Observation of Retained Austenite Amount of Repeatedly Induction Heated SUJ2 Bearing Steels

Martensitic high-carbon, high-strength bearing steel is used for rolling contact applications when high wear and fatigue resistance are required. Due to its high fatigue strength, SUJ2 is not used for only bearings but for shafts. The objective of this work is a clarification of the relationship between quenching times and retained austenite amount of SUJ2 steel. It was found that repeatedly induction heating increased the retained austenite amount, but did not change the Vickers hardness.

Granular bright fact crack propagating under very high cycle fatigue

The different crack initiation modes from different internal defects of a high carbon chromium bearing steel are investigated in the present paper. The relative granular bright facet (GBF) size is approximately proportional to . The critical applied stress intensity factor range at the periphery of inclusion ΔKinc,th, above which the GBF will no longer be formed, was obtained. For the present SUJ2 steel, ΔKinc,th = 8 MPa m1/2. The crack growth process in GBF is further investigated by the low–high two-step variable amplitude loading tests. The crack growth process in GBF can be described by . The exponent m0 is a material constant independent of the applied stress amplitude and the inclusion size and increases with increasing of HV.

Effect of Twice Quenching on Prior Austenite Grains and Rotating Bending Fatigue Cracks in SUJ2 Steel

Martensitic high-carbon high-strength SUJ2 bearing steel has been widely used as a main alloy for rolling contact applications, and also in components under bending and tension-compression. In order to enhance the material’s strength, refining the prior austenite grain size through repeated-heating was investigated in our previous work. In this work, we observed the microstructure of twice quenched N-rich SUJ2 steel and performed their rotating bending fatigue tests. It was found that most of cracks on the fracture surface originated from Al2O3 inclusions.

A fracture mechanics approach to interior fatigue crack growth in the very high cycle regime

Growth rates of optically dark areas (ODA) and fish-eyes (FE) were quantified in kHz-ultrasonic fatigue tests on SUJ2 and 17-4PH steels at constant and repeated two-step amplitudes. Sizes of ODAs and FEs depended on the stress intensity factor (SIF) range, and interior fatigue crack growth rates (FCGR) were slower than those of “long” cracks in air, suggesting vacuum as ODA growth environment. Repeated two-step tests on SUJ2 steel served to form beach marks so that, a quantification of ODA sizes, interior FCGRs and SIFs became possible. Additional FCGR measurements of long cracks in vacuum and comparable fracture morphologies allowed estimating the growth rates of ODAs and FEs in 17-4PH steel.

2206 SUJ2高周波焼入れ歯車の曲げ疲労強度に及ぼす加熱時間,前処理および焼戻しの影響(OS-02 歯車の強度/OS-16 一般講演)

Macro and micro-structure and hardness of hardened layer of induction hardened SUJ2 steel gears were measured, and profiles of hardened layers and effective hardened depths were obtained. Bending fatigue tests of induction hardened SUJ2 steel gears were carried out and S-N curves and bending fatigue limits were obtained. On the basis of these results, effects of heating time, pre-treatment and tempering on effective hardened depth and bending fatigue limits of induction hardened SUJ2 steel gears were clarified. Furthermore, these results were also compared with those of induction hardened S35C steel gears.

Effect of Size and Depth of Small Defect on the Rolling Contact Fatigue Strength of a Bearing Steel SUJ2

Effect of Size and Depth of Small Defect on the Rolling Contact Fatigue Strength of a Bearing Steel SUJ2

Investigation of Crack Initiation and Propagation during Rolling Contact Fatigue of SUJ2 Steel Bearings Using a Newly Developed One-Point Testing Machine

An innovative type of one-point rolling contact fatigue (RCF) machine was developed in order to investigate crack initiation and propagation in metals. The microstructural changes and propagation of subsurface cracks during rolling contact in specimens tested by using the new device were studied by laser confocal microscope and X-ray diffraction. It was shown that this new method presents several important advantages compared to the conventional thrust type RCF machines.

Investigation of Crack Initiation and Propagation during Rolling Contact Fatigue of SUJ2 Steel Bearings Using a Newly Developed One-Point Testing Machine

An innovative type of one-point rolling contact fatigue (RCF) machine was developed in order to investigate crack initiation and propagation in metals. The microstructural changes and propagation of subsurface cracks during rolling contact in specimens tested by using the new device were studied by laser confocal microscope and X-ray diffraction. It was shown that this new method presents several important advantages compared to the conventional thrust type RCF machines.

Bearing Fatigue Life Tests of Two Advanced Base Oils for Space Applications Under Vacuum and Atmospheric Environments

Four series of rolling-element bearing fatigue tests were conducted with 51104 size thrust ball bearings with three balls made from SUJ2 (AISI 52100) steel lubricated with two advanced synthetic base oils used for space applications. The test lubricants were perfluoropolyether (PFPE) and multiply alkyated cyclopentane (MAC). Each oil was tested with bearings under vacuum and atmospheric environments. The bearings were tested at a maximum Hertzian stress of 4 GPa on the inner and outer races. The outer race was rotated at a speed of 250 rpm. A pool lubrication system was used. Fresh lubricant was used for each test bearing. Testing in vacuum conditions was at 5 × 10−2 Pa. The test oils were analyzed to determine whether changes occurred as a result of operating in air and in a vacuum. In a vacuum environment, the PFPE 815Z oil exhibited a longer fatigue life than the MAC 2001A oil. However, in an air environment, the MAC 2001A oil had a longer L10 fatigue life than the PFPE 815Z oil. The fatigue life tests of PFPE 815Z oil in vacuum resulted in a longer L10 life than when tested in an air environment. In an air environment, hydrogen fluoride was generated in the bearing tests with the PFPE 815Z oils. Under vacuum conditions, hydrogen fluoride was not generated with the PFPE 815Z oil, resulting in longer bearing fatigue lives. The fatigue life tests of MAC 2001A oil in a vacuum resulted in shorter L10 fatigue life than in an air environment. The shorter life was attributed to the lower elastohydrodynamic oil film formation with the MAC 2001A oil because of a higher operating temperature and decomposition of the oil in vacuum.

TRIBOLOGICAL CHARACTERISTICS OF RADIAL JOURNAL BEARINGS BY ULTRASONIC NANOCRYSTAL SURFACE MODIFICATION TECHNOLOGY

Ultrasonic nanocrystal surface modification (UNSM) has applied to a radial journal bearings made of bearing steel SUJ2. Mechanical characteristics are compared between UNSM treated and untreated bearings. Friction torque is measured at the boundary lubrication condition, the mixed lubrication condition, and the full hydrodynamic lubrication condition. The peak torque at the boundary lubrication condition and the transition period to mixed lubrication condition on the UNSM treated samples are reduced. These effects are very useful to improve the service life of journal bearings. The Stribeck curve at the mixed and full hydrodynamic lubrication is derived and compared. The friction coefficient at these two regimes is reduced by more than 50%, which will do effective role for improvement of energy efficiency. The major effects for this reduction at three lubrication regimes could be explained in the terms of micro dimple surface.

Friction and wear properties on AZ91D magnesium alloy treated by anodizing from phosphate electrolytic solution

The effects of various surface treatments on the friction and wear properties of AZ91D magnesium alloy substrate against the SUJ2 steel ball were evaluated by using a horizontal reciprocating friction and wear test apparatus. The friction and wear properties greatly changed due to the type of surface treatment in spite of being under equal friction and wear testing conditions. Wear loss of AZ91D magnesium alloy anodized from the phosphate solution was greatly reduced in comparison with the other surface treatments such as Dow17, conversion coatings and also no surface treatment. The above results suggest that anodizing from the phosphate solution should improve the friction and wear properties of magnesium alloy used for sliding parts.

Microstructure and Mechanical Performance of Brand‐New Al0.3CrFe1.5MnNi0.5 High‐Entropy Alloys

The microstructure, hardening behavior, and adhesive wear behavior of Al0.3CrFe1.5MnNi0.5 high-entropy alloys were investigated. All alloys exhibit superior adhesive wear resistance to cast iron FC-300, bearing steel SUJ-2, and hot-mold steel SKD-61. The superior wear resistance of the alloys is attributable to the formation of ρ phase during the furnace cooling from the homogenization at 1100 °C or the in situ formation of the ρphase induced by the high interface temperature and severe plastic deformation during wear sliding.

Effects of Residual Gas on Tribochemical Reactions of SUJ2 Steel in Vacuum and in Argon Gas Atmosphere

To analyze the mechanisms of tribochemical reactions occurring between atmospheric gases and materials induced by friction, the authors have developed a friction test system with integrated XPS. The system can analyze worn surfaces in various environments using XPS without air exposure. The results of friction tests in vacuum showed that the native oxide film that formed on the bare surface was worn by friction in vacuum. The results of the friction tests in an Ar gas atmosphere also showed the same results as the friction tests in vacuum. However, it has been suggested that some tribochemical reactions with trace amounts of residual gas occur during friction tests in an Ar gas atmosphere. The results of the friction tests and XPS analyses indicated that our friction test system with integrated XPS was useful for analyzing tribochemical reactions between atmospheric gases and materials.

Effects of material strain rate sensitivity in low speed impact between two identical spheres

This paper investigates the effects of strain rate sensitivity on the impact of two identical spheres. The spheres made of SUJ2 steel were impacted by using pendulum setup. The coefficients of restitution (COR) and contact durations were obtained experimentally. Static tensile test and Split Hopkinson pressure bar tests were conducted to identify the material properties of the sphere. And finite element simulations of the impacts between two identical spheres were carried out using LS-DYNA software. The simulation results fit well to the experimental results and they were compared to the results of elasto-plastic simulations which ignored the material strain rate sensitivity. It was found that the strain rate sensitive sphere showed the higher COR than those from the sphere which ignored the material strain rate sensitivity. Therefore, the material strain rate sensitivity has remarkable effect on the impact of two identical spheres even in the low speed impact. However, the influences of the material strain rate sensitivity on the contact durations were small.

Evaluation of Sliding Wear Resistant Property of C.P. Titanium and SP-700 Titanium Alloy Surface-hardened by Ar–5%CO Gas

Sliding wear resistant properties of C.P. titanium and SP-700 alloy surface-hardened by Ar–5%CO gas were evaluated using a counterpart material of a bearing steel, JIS SUJ-2 steel and Nishihara type of sliding wear testing machine. In the latter, two disk specimens were rotated at different rotating speeds under a given compressive applied load, yielding a sliding ratio of 20%. Wear tests were repeated intermittently for several times, and a respective test time period in each series of wear tests was primarily varied. The mass loss in both disks was measured after each test. Wear resistance of annealed C.P. titanium without surface hardening was inferior to that of annealed SUJ-2 steel, but surface hardened C.P. titanium resulted in superior wear resistance over quench-tempered SUJ-2 steel with a hardness of 720 in Hv. Observation results of worn surfaces in both disks indicate that preferential wear occurred in the convex region of a furrow-like pattern formed by a lathe machining, resulting in a reduction of surface roughness values with wear progress. When a respective test time period was extended to 21.6 ks, adhesive wear took place between worn surfaces in both specimens, and the mass loss ratio in titanium disk increased at a much higher rate compared with that of a respective test time period of less than 14.4 ks. The steel debris torn off from worn surface of SUJ-2 steel disk was observed to adhere to the worn surface in surface hardened C.P. titanium disk. Wear resistant property of surface hardened SP-700 alloy was also superior to quench-tempered SUJ-2 steel.