Steel SAE Research Articles

Torsional fatigue behaviour and damage mechanisms of martensitic spring steel in the HCF regime

This study investigates the fatigue behaviour and damage mechanisms of the martensitic spring steel SAE 9254, with emphasis on short crack propagation. Shear stress-controlled torsional fatigue tests are performed at stress ratio R = -1 and test frequency f = 79 Hz using structure-sensitive measurement techniques to detect the relevant damage mechanisms. An in-situ torsional fatigue testing device is applied for shear-controlled fatigue tests at two amplitudes of the torsion angle using R = –1 and f = 5 Hz, and the microstructural-dependent short crack propagation path is documented by means of confocal laser microscopy and electron backscattering analysis. It is found that the early development of fatigue damage is characterised by the formation of slip bands, which serve as crack initiation sites. In this process, crack initiation occurs preferentially at or near prior austenite grain boundaries. Furthermore, prior austenite grain boundaries were identified as obstacles for the propagation of short cracks, because of the change of the crystallographic orientation leading to an oscillating propagation rate of short cracks. The short crack density ρCD, which is an important parameter for fatigue damage, is rapidly growing with increasing shear stress amplitude ΔτT/2 and reveals a stress type specific behaviour.

Effect of austenitisation and tempering treatments on the mechanical properties of advanced high strength spring steel SAE 9254

In response to increasingly stringent global regulations within the automotive industry, there is a growing demand for lightweight yet high-strength steel suspension coil springs. This study undertakes a comprehensive examination of the critical factors influencing the mechanical properties of SAE 9254, a well-established spring material, in its quenched and tempered (QT) state. The primary objective is to optimise its strength and ductility, especially in high-performance applications with an emphasis on lightweight design. The investigation encompasses a detailed exploration of the effects of varying austenitisation temperature (AT) and austenitisation time (At) on the microstructure and mechanical properties of the steel. Of particular interest is the study of tempering temperatures ranging between 300°C and 350°C to elucidate the mechanisms responsible for enhancing the steel's strength. Notably, the findings highlight dislocation density as the primary factor driving the strengthening of martensitic spring steel. Furthermore, the pivotal role of austenite grain size before quenching becomes evident, influencing toughness, ductility, martensite block size, and the percentage of retained austenite (γR). This study provides valuable insights into optimising the mechanical properties of SAE 9254 spring steel for high-performance applications, achieving ultimate tensile strengths (UTS) exceeding 2100 MPa and a reduction in area (RoA) exceeding 30%. Notably, the properties attained for this grade are comparable to those achieved with microalloying additions. Consequently, this research underscores the significance of controlling austenite grain size and dislocation density as critical factors for tailoring the properties of martensitic steels, positioning them as competitive materials, particularly in the pursuit of lightweight design.

DLC/a-Si:H multilayers films to improve wear resistance of components of common rail injection system

The Common Rail Injection System (CRIS) is diesel engines' main fuel injection system. Due to market needs, such as replacing fuel from diesel to biodiesel, several mechanical problems were observed, including the wear of the metallic components. This paper proposed improving the wear resistance of steel SAE 1045, which can be used in some elements of injection systems, by depositing DLC multilayer films using a plasma Duplex treatment. Firstly, the samples were nitrided in atmospheric plasma and then coated with thin films of DLC/a-Si:H multilayers using a modified pulsed-DC PECVD system. The duplex treatment may reduce friction and consequently facilitate sliding contact. The tribological tests were performed in a cylinder-disc tribometer designed and constructed exclusively to simulate the real contact of components under pressure and movement conditions in the CRIS. The results showed a considerable increase in surface hardness due to the formation of iron nitrides. The DLC/a-Si:H coating reduced the surface roughness because of the plastic deformation of this layer after the tribological tests. Also, this mechanism contributed to the decrease in wear and improved performance of the studied component.

Microstructural-based analysis of the unexpected differences in rolling contact fatigue behavior between SAE52100 and SAE4320

The rolling contact fatigue (RCF) of both a high carbon through-hardening bearing steel (SAE52100) and a low carbon case-hardening bearing steel (SAE4320) have been investigated using RCF. The RCF-life for the SAE4320 steel was found to be ≈7.0 × 107 cycles, about 7 times higher than the RCF-life found for the SAE52100 steel of ≈ 1.0 × 107 cycles. Measurements from fracture surfaces of specimens tested to failure in rotatory bending fatigue tests revealed an average inclusion size of 27.3 μm for SAE52100, and 38.2 μm for SAE4320, indicating a lower purity for case-hardening bearing steel, and suggesting SAE4320 should have a shorter RCF-life, contrary to the measured RCF-lives. However, the carbide size, the prior austenite grain size and the retained austenite (RA) volume fraction for SAE4320 were measured as 0.20 μm, 10.8 μm and 25.0%, respectively, all of which are better than those for SAE52100 (0.59 μm, 16.1 μm and 3.1%). The enhanced RCF-life can be understood as a combined result of the detrimental effects of inclusion size and the beneficial contribution of the refined carbide and prior austenite grain size and of the increased austenite volume fraction. Based on this study, it is proposed that a double refinement of both carbide and prior austenite grain size, together with control of the austenite fraction, may be a promising way to extend RCF-life without the requirement for further inclusion refinement during the fabrication high-performance bearing steels.

StressLife: A Short-Time Approach for the Determination of a Trend S-N Curve in and beyond the HCF Regime for the Steels 20MnMoNi5-5 and SAE 1045.

Within the scope of this research, a new short-time procedure designated as StressLifeHCF was developed. Through a combination of classic fatigue testing and non-destructive monitoring of the material response due to cyclic loading, a process-oriented fatigue life determination can be carried out. A total of two load increases and two constant amplitude tests are required for this procedure. By using data from non-destructive measurements, the parameters of the elastic approach according to Basquin and the plastic approach according to Manson-Coffin were determined and combined within the StressLifeHCF calculation. Furthermore, two additional variations of the StressLifeHCF method were developed in order to be able to accurately describe the S-N curve over a wider range. The main focus of this research was 20MnMoNi5-5 steel, which is a ferritic-bainitic steel (1.6310). This steel is widely used for spraylines in German nuclear power plants. In order to validate the findings, tests were also performed on an SAE 1045 steel (1.1191).

Surface roughness and morphology evaluation of bearing steel after grinding with multilayer graphene platelets dispersed in different base fluids

Bearings are widely used in different industries which demand different quality requirements to ensure a long life with low wear rates. In this sense, bearing components should present combination of low surface roughness and tight dimensional deviations, as well as good lubricant retention capacity. So, grinding is an alternative to achieve this combination, however, one of the challenges is the large amount of heat generated in the grinding wheel-workpiece interface when using conventional abrasives grinding wheels, which can lead to surface finish deterioration and thermal damages, thereby reducing the component's life. Thus, several cooling-lubrication techniques have been tested in the past decades to enhance the cooling-lubrication properties of cutting fluids, with a highlight in recent years for the benefits of adding solid particles with good tribological properties to improve grinding efficiency. In this context, this work sought to evaluate the roughness and surface morphology of the bearing steel SAE 52100 (60 ± 2 HRC) after grinding with multilayer graphene (MLG) platelets dispersed in two different cutting fluids (synthetic and semi-synthetic). Tests with traditional MQL (without solid particles) and conventional techniques (flood) were also carried out for comparison. The output variables investigated were surface roughness parameters Ra, Rz, Rku, Rsk, Rk, Rpk, and Rv, images of machined surfaces through a scanning electron microscope (SEM), and the specific grinding energy. The results indicated that the base fluid type significantly affected the grinding performance. Tests with semi-synthetic fluid having MLG decreased the Ra parameter of the ground surface by 9% compared to the traditional MQL technique, with a higher Rvk and negative skewness. For the synthetic fluid also with MLG, about 29% increase in the Ra parameter was observed compared to MQL without nanoparticles, although it resulted in higher values of Rpk with more positive skewness. Presence of MLG in semi-synthetic and synthetic fluids reduced the specific grinding energy by 7% and 14%, respectively. Also, less intense plastic deformation and material adhesion was observed when grinding with MLG.

The Effect of PEO Treatment in a Ta-Rich Electrolyte on the Surface and Corrosion Properties of Low-Carbon Steel for Potential Use as a Biomedical Material

Fe-based materials have extensive applications in the building and automobile industries due to their excellent mechanical properties and low cost. However, their biomedical employment is restricted by the corrosion propensity when in contact with bodily fluids. In this study, single-step Plasma Electrolytic Oxidation, PEO, treatment in Ta-rich electrolyte was used, for the first time, to improve the corrosion resistance of low-carbon steel SAE 1020 for possible use as device implants. The effect of the applied voltage on the chemical and phase composition, topography, wettability, roughness, and corrosion properties were addressed. The results indicated that the Fe-based oxide coatings had a rough and hydrophilic surface, increasing the Ta content with the applied potential. The phase composition of the coatings was mainly composed of hematite (Fe2O3), with the Fourier-transform Infrared Spectroscopy, FTIR, spectrums indicating the presence of some absorbed water and organic molecules. The corrosion resistance of the PEO-treated samples was better than the substrate against saline solution (0.9% NaCl) due to the Fe2O3 growth decorated with Ta particles, especially the sample treated at 200 V. The results state that Ta-enriched Fe-based oxide coatings could significantly improve the applicability of low-carbon steel SAE 1020 as a low-cost biomaterial, particularly for medical devices.

Crashworthiness performance of hybrid energy absorbers using PET-G honeycomb structure

The authors report an experimental investigation on square thin-walled energy absorbers with different topologies and materials. The material was steel SAE 1010 and aluminum AL 6160. Some samples non-filled and filled with polymeric material received patterned windows placed in opposite faces with specific dimensions: 20x20, 15x30, and 20x30 mm2. Quasi-static axial loading crushes hollow specimens and hybrid specimens filled with PET-G honeycomb. The core filling was printed using the FDM technique. The crashworthy ability of specimens was evaluated based on the specific energy absorption (SEA), load ratio (LR) and structural efficiency (η), which showed that windowed-filled specimens with 20x30 mm2 perform better. The maximum increase of SEA was 212%, LR decreased from 4.02 to 1.78 and η increased from 0.45 to 0.89 for steel energy absorbers and in the same manner, the values for aluminum specimens were 123%, 2.97 to 1.28 and 0.46 to 0.71. The effects of the patterned windows and their combination with the honeycomb core for both metallic materials show that such a topology improved the performance in two factors. The windows reduced the peak force, and the PET-G honeycomb furnished a smoothing to the region at the end of the fold formation, contributing to the crashworthy ability. Future work envisages experimental testing of the samples in dynamic tests.

Niobium- and titanium-based coating for the protection of carbon steel SAE 1020 against corrosion

PurposeThe purpose of this paper is to evaluate the protection against corrosion of carbon steel SAE 1020 promoted by a niobium- and titanium-based coating produced from a resin obtained by the Pechini method.Design/methodology/approachA resin was prepared with ammonium niobium oxalate as niobium precursor and K2TiF6 as titanium precursor. Carbon Steel SAE 1020 plates were dip coated in the resin and calcinated for 1 h at 600 ºC. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were used to characterize the coating morphologically and structurally. Open circuit potential, electrochemical impedance spectroscopy, anodic potentiodynamic polarization and scanning vibrating electrode technique were used to evaluate the corrosion protection of the coating.FindingsThe electrochemical analyses evidence slight protection against corrosion of the coating by itself; however, the needle-like crystal structure obtained may potentially provide a good anchorage site, suggesting the coating could be used as a pretreatment that may present similar application to phosphating processes, generating lower environmental impacts.Originality/valueDue to increasingly restrictive environmental laws, new environmentally friendlier surface treatments must be researched. This paper approaches this matter using a combination of niobium- and titanium-based coating, produced by a cleaner process, the Pechini method.

Application of optimized lubri-cooling technique in through-feed centerless grinding process of bearing steel SAE 52100

Application of optimized lubri-cooling technique in through-feed centerless grinding process of bearing steel SAE 52100

Research on calculation of grinding surface roughness

In machining processes, grinding is often chosen as the final machining method. Grinding is often chosen as the final machining method. This process has many advantages such as high precision and low surface roughness. It depends on many parameters including grinding parameters, dressing parameters and lubrication conditions. In grinding, the surface roughness of a workpiece has a significant influence on quality of the part. This paper presents a study of the grinding surface roughness predictions of workpieces. Based on the previous studies, the study built a relationship between the abrasive grain tip radius and the Standard marking systems of the grinding wheel for conventional and superabrasive grinding wheels (diamond and CBN abrasive). Based on this, the grinding surface roughness was predicted. The proposed model was verified by comparing the predicted and experimental results. Appling the research results, the surface roughness when grinding three types of steel D3, A295M and SAE 420 with Al2O3 and CBN grinding wheels were predicted. The predicted surface roughness values were close to the experimental values, the average deviation between predictive results and experimental results is 15.11 % for the use of Al2O3 grinding wheels and 24.29 % for the case of using CBN grinding wheels. The results of the comparison between the predicted model and the experiment show that the method of surface roughness presented in this study can be used to predict surface roughness in each specific case. The proposed model was verified by comparing the predicted and measured results of surface hardness. This model can be used to predict the surface hardness when surface grinding

Taguchi based parameter optimization for cutting force reduction in SAE 1045 steel machining with nanofluid

Utilization of Kerala chips shop’s waste of ‘used coconut oil’ is considered its natural lubricating properties. This piece of research investigating the effects of Nano Acidum Boricum powder enriched waste coconut oil on diminishing cutting forces while machining SAE1045 steel. The performance of nanofluid effects on machining is compared with its conventional practice of green machining. As waste is utilized to prepare bio degradable nanofluid for employing for better machinability. This process named as clean machining. The machining outcomes on SAE1045 steel work were compared with t-test. This investigation considered depth of cut, cutting speed and tool feed rate at three levels Taguchi L27 orthogonal array was utilized.. Taguchi analysis considered for optimizing the machining parameters with the sense of surface roughness. The ANOVA utilized to analyses the observations, influence of various input factors and their levels. It was found that the proposed method reduces the surface roughness considerably. By altering the cutting speed, the required cutting force could be met than the tool feed rate.

Experimental analysis on Feed force reduction performance by Nanofluid of Graphene Nano platelets enriched Waste Coconut Oil in wet Machining of SAE 1045 Steel Shaft

The Waste utilization is one of the prime importance and possess good social impacts. Here the used coconut oil which disposal as waste at Kerala chips shop is utilized for preparing a novel Nano fluid for machining purposes. Such Nano fluid can be alternatively used for lubricating purpose for machining the precision shaft. This piece of research work prepared Nano fluid by concentrating Graphene Nanoplatelets with used coconut oil (waste). The synthesized nanofluid used as coolant in machining SAE1045 steel work material. The range of inputs were adapted from the conventional dry machining practices and manufacturer catalogue of the material. As planned to investigate the three key input variables at 4 levels from minimum to maximum in the selected range, the Taguchi L16 orthogonal array was preferred to design the experiments. The t-test employed for comparing the machining environment (a kind of input variable) performance through 16 different input combinations and found that the proposed intervention is outperformed significantly. So, the parameters for the proposed machining practice was optimized and input factors’ contributions were analyzed by means of Taguchi analysis and ANOVA.

Reconnoitering the influence of nanofluid of GnPs enriched waste coconut oil in machining SAE 1045 shaft on modification surface finish

The surface quality is a prime factor in the failures of shaft by fatigue load. Here used coconut oil that is waste coconut oil disposal severities shop of ‘Kerala chips’ are used for preparing nanofluid for machining coolant. Hence this piece of research work investigating the effect of Nano fluid of graphene nanoplatelets (GnPs) enriched waste coconut oil in minimizing Surface Roughness while machining SAE1045 steel shaft by conventional lathe. Control group samples processed by dry (green) machining. The intervention group samples machined by 0.3% GnPs concentrated used coconut oil employed in the flood cooling form for the machining that is clean technology approach. Taguchi analysis and ANOVA used for optimizing the process parameters and developing mathematical model. From the experimental results it was revealed that the proposed GnPs concentrated used coconut oil nanofluid coolant reduced surface roughness significantly by 33.539% and confirmed observations are perfect and obeys statistical assumptions. Hence the same can be recommended to process the SAE 1045 material for shaft manufacturing.

Comprehensive review on improvement in surface properties of bearing steel

This paper presents the review of various techniques used to improve surface properties of bearing steel SAE 51200. The selection of method depends on solubility, adhesion or bond strength between foreign material and the core/substrate material surface. To improve the various tribological properties, the studies of various past and current technologies and also selection of the best treatment for different bearings used under specific service conditions are reviewed in this paper. One important part is material to be deposited and second important part is by which method the material is deposited. Various coating materials used are Titanium Nitride (TiN), Titanium Carbo Nitride (TiCN) and Titanium Aluminium Nitride (TiAlN), Thin chrome-nitride, Diamond-like carbon (DiC), Carbide–chromium–nickel WC– (W, Cr)2C–Ni) coating, Single-layered TiN and a multi- layered (TiN–NbN, TiN–TaN, TiN–CrN) coating. The different processes used are Thermal Spraying (TS), Combustion flame spraying, Physical vapour deposition (PVD), Chemical vapour deposition (CVD), Ion-beam-assisted deposition (IBAD), Reactive mag- neutron sputtering (RMS), Plasma Spraying (PS) are discussed in details. The Rolling contact fatigue life depends on the compressive forces induced in bearing material. Surface modification technology plays an important role in improvement in life of bearing.

Determination of fatigue lifetimes with a micromechanical short crack model for the high-strength steel SAE 4150

Generalization of microstructural short crack (MSC) growth simulation across different loading conditions and materials is often not considered in literature. These points are addressed by transferring a previously proposed model for crack initiation and transgranular MSC growth from ferritic steel to the martensitic steel SAE 4150. An accurate depiction of the microstructure is achieved by a novel approach to parameterize martensitic tessellations. Calculated fatigue lifetimes are in similarly good agreement with experimental data for martensite as for previously considered ferrite. The model’s transferability is shown among distinct load ratios and between strain- and stress-controlled loading, subject only to small deviations.

An investigation of accelerated graphitisation kinetics to improve the machinability of an experimental medium-carbon free-machining steel

Recent studies have shown that the graphitisation process in a medium‑carbon steel during high temperature annealing can be accelerated by alloying; the key alloying additions are Si and Al. In addition, the nucleation, morphology and dispersion of graphite particles or nodules are observed to be affected by the pre-anneal microstructure, for example, either ferrite-pearlite, bainite or martensite, as well as the annealing time. The accelerated graphitisation kinetics and microstructural effects are revealed by light optical and electron microscopy, and in parallel with this, are also reflected by the hardness values as dictated by the normal tempering reactions and balance between the graphite and remaining carbides. Thus the extent of graphitisation is shown to influence the machinability of the experimental carbon steel. Indicative machinability was measured by tool wear during drill testing. The drill tests also indicated that optimisation of steel composition and heat treatment could potentially develop promising machinability comparable to existing commercial free-machining steel SAE 1117. Under the conditions of the drill tests conducted, graphitising from the starting bainitic microstructure also resulted in measured tool wear not too dissimilar to that of leaded free-machining steel SAE 12L14.

Calculation of the Fatigue Limit of High‐Strength Steel Specimens at Different Loading Conditions Based on Inclusion Sizes

A calculation method for the fatigue limit of components made of high‐strength steels that fail at inclusions is described. The method consists of two parts: first, the size of failure‐critical inclusions is determined based on metallographic investigations. Then, the fatigue limit is determined based on the expected inclusion sizes using a fracture mechanics model. Influencing factors such as sample size, heat‐treatment conditions, and mean stresses are considered. The model parameters are derived from fatigue test data collected over decades within the framework of several research projects. The dominant influencing factors are the inclusion size and the hardness of the steel matrix. Finally, the model is used to predict the fatigue limit of different specimens made of a bearing steel SAE 52 100. The sizes of failure‐critical inclusions and fatigue limits calculated with the model are compared and evaluated on the basis of the inclusion sizes found in the samples’ fracture surface and the experimentally determined fatigue limits.

Thermal Stability of Residual Stresses in Differently Deep Rolled Surface Layers of Steel SAE 1045

The stability of compressive residual stresses generated by deep rolling plays a decisive role on the fatigue behavior of specimens and components, respectively. In this regard, deep rolling at elevated temperature has proven to be very effective in stabilizing residual stresses when fatigue analysis is conducted at ambient temperature. However, since residual stresses can be affected not only by plastic deformation but also when thermal energy is provided, it is necessary to analyze the influence of temperature and time on the relaxation behavior of residual stresses at elevated temperature. To evaluate the effect of deep rolling at elevated temperatures on stability limits under thermal as well as combined thermo-mechanical loads, the present work introduces and discusses the results of investigations on the thermal stability of residual stresses in differently deep rolled material conditions of the steel SAE 1045.

Real-time stress evolution during laser surface line hardening at varying maximum surface temperatures using synchrotron X-ray diffraction

Multiple laser surface line hardening experiments on flat samples, made of tempering steel SAE 4140, were carried out under variation of the maximum control temperature in the range of 850 °C to 1150 °C at the sample surface. For each temperature, time resolved X-ray diffraction measurements using synchrotron radiation were performed at beamline P05@PETRA III at DESY (Deutsches Elektronen Synchrotron) in Hamburg, Germany. The samples were line hardened using a 4 kW High Power Diode Laser unit at a constant laser feed of 800 mm/min with a specific laser optics under pyrometer control of the maximum surface temperature. A special designed process chamber with 4 symmetrically attached fast silicon micro strip line detectors allows for stress analysis during the process according to the sin2ψ method in single exposure mode with a measurement frequency of 50 Hz. As a result of the time resolved analyses the elastic strains were separated from thermal ones and near surface local stress evolutions, longitudinal and transverse to the laser track direction in the center of the processed zone, were determined. The in situ experiments were complemented by high spatially resolved post-process residual stress analyses using conventionally generated X-rays and by metallographic investigations. The results are carefully discussed regarding mechanisms of local stress formation during the laser hardening process and their dependence on the maximum control temperature. The temporal stress course during laser surface line hardening is presented for the first time in both surface parallel directions, where temperature differences in the process zone lead to significant differences in the resulting residual stress profiles. In addition to the common validation of process simulations by comparison with experimentally determined data from the final state after processing, e.g. the resulting local residual stresses, the current work provides real-time data from in situ experiments during laser surface hardening for the validation of temporal stress courses of numerical process simulations.