Depth Of Hardened Layer Research Articles

Characterization of surface integrity of 7075-T6 aluminum alloy subjected to microbiologically induced corrosion during high-speed machining

Microbiologically Influenced Corrosion (MIC) is one of the primary causes of corrosion damage and equipment failure in industrial environments. This paper aims to investigate the impact of microbiologically influenced corrosion on the surface integrity of 7075-T6 aluminum alloy. Through experiments involving cryogenic treatment and machining, the study systematically compares the effects of different microbiologically influenced corrosion environments on 7075-T6 aluminum alloy. Techniques such as X-ray Diffraction (XRD), surface roughness measurement, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), and work hardening were used to elucidate the influence of natural seawater (Planktonic microorganisms, PM) and marine sediment (Benthic microorganisms, BM) corrosion on the surface integrity of 7075-T6 aluminum alloy.The results indicate that, compared to PM corrosion, BM corrosion results in a smaller surface roughness of 7075-T6 aluminum alloy. Specifically, the BM-10d specimen exhibits the smallest roughness at 0.353 μm. XRD and EDS analyses show that the corrosion products after microbiological corrosion are primarily a mixture of Al2O3, AlO(OH), and Al(OH)3. The peak intensity of AlO(OH) in the (200) crystal plane of the BM-5d corrosion product is notably higher than that of the 7075-T6 aluminum alloy under other conditions. In the PM environment, the corrosion products fully cover the entire surface of the workpiece and are accompanied by significant cracking. In contrast, in the BM environment, the corrosion products mainly exhibit a granular structure, are scattered across the workpiece surface, and the exposed substrate can be observed.The microhardness of the aluminum alloy after microbiological corrosion shows a trend of increasing initially, then decreasing, and finally stabilizing. The maximum depth of the hardened layer for PM-10d is 120 μm, with a maximum hardness of 178.74 HV. Compared to PM corrosion, BM corrosion results in a significantly greater hardened layer depth for 7075-T6 aluminum alloy, with the BM-10d hardened layer depth reaching approximately 140 μm and the peak hardness at 185.36 HV. Additionally, in the BM environment, the precipitates are fewer compared to those in the PM environment and exhibit a non-continuous, non-grain-boundary precipitation band.

Composite effects of residual stress and hardness gradient on contact fatigue performance of rough tooth surfaces and optimization design of detailed characteristic parameters

Residual stress and hardness gradient significantly affect the contact fatigue failure process of rough tooth surfaces, and the meticulous design of their characteristic parameters can help improve the fatigue resistance of gears. In this paper, an efficient computational method for rough tooth surface contact is established based on the reconstruction modeling of asperities and mixed lubrication analysis. By comprehensively considering the effects of residual stress and hardness gradient, the Dangvan multiaxial fatigue criterion is adopted to predict and analyze the contact fatigue life of the gear surface. The correlation between the surface residual stress, maximum residual stress depth, surface hardness, and effective hardening layer depth, among other characteristic parameters, and the contact fatigue performance of tooth surfaces is established. The results show that: (1) Increasing the magnitude of surface residual compressive stress and surface hardness can significantly reduce the risk of fatigue failure in the near-surface layer of the gear. To achieve the same fatigue performance, there is a linear negative correlation between the design values of the two parameters. (2) Affected by the double stress peaks in the rough tooth surface stress field, the maximum residual stress depth significantly affects the depth at which the highest failure risk occurs. With changes in roughness, the optimal design value of the maximum residual compressive stress depth changes from about 0.5 times the Hertzian contact half-width depth in the subsurface layer (Sa < 0.2 μm) to about 15 μm in the near-surface layer (Sa > 0.4 μm). (3) Considering both process cost and gear surface fatigue resistance, the design threshold for the effective hardening layer depth should be greater than the Hertzian contact half-width. This paper establishes a composite correlation between the meticulous characteristic parameters of residual stress, hardness gradient, and the contact fatigue performance of tooth surfaces, providing theoretical support for optimal design of tooth surface anti-fatigue performance.

Features of hardening of the case parts made of aluminium alloys

The dependence of the hardened layer depth on the modes of superficial treatment is experimentally investigated, with the purpose of evaluation of known laws of initial linear contact of the strengthening part and the tool. The method of the definition of optimum loading on strengthening tool (the steel cylindrical roller) and its radius at static stamping is offered. The technique is examined with the reference to the case parts made of aluminum alloys.

Effect of ultrasonic surface rolling on the friction and wear properties of 8620H carburized steel at elevated temperatures

The surface strengthening treatment of 8620H carburized steel was carried out by ultrasonic surface rolling (USR) process, and the samples with and without the treatment were subjected to friction and wear experiments at 25°C, 100°C, and 150°C. The experimental results showed that the samples with USR treatment had higher surface hardness, lower surface roughness, deeper hardened layer depth, and higher surface residual compressive stress than the samples without USR treatment. Meanwhile, the wear degree of the samples deteriorated as the temperature increased, but the anti-wear performance of the samples with USR treatment increased by 52.9%, 29.8%, and 14.9% compared with the samples without USR treatment at 25°C, 100°C, and 150°C, respectively, indicating that the USR treatment still had a better strengthening effect at high temperatures.

Влияние предварительной плазменной обработки поверхности стали 09Г2С на формирование покрытия в результате горячего цинкования

In recent years, the range of silicon-containing steels subjected to hot galvanizing has been expanding. Alloying of steel with 0.5–1 % of silicon leads to the formation of a zinc coating of great thickness with a matte or multi-colored surface. This is associated with the changes in phase reactions between iron and zinc in the Fe–Zn–Si system. The development of ways to neutralize the negative influence of silicon on the formation of zinc coating is an urgent task. The purpose of the work is to study the influence of preliminary plasma cutting and plasma surface hardening of 09G2S (S355J2) steel on the thickness and structure of zinc coating formed on treated surfaces. It was found that after plasma cutting, the structure of the surface layer of steel is martensite, and after plasma surface hardening, it is martensite and ferrite. Analysis of the change in microhardness from the steel surface to the middle showed that the hardened layer depth is 400 μm. A zinc coating consisting of a δ-phase and a ζ-phase is formed on the surface of the steel without pretreatment. On the surface of the steel after plasma treatment, a zinc coating is formed characteristic of low-silicon steels and consisting of the δ-phase, ζ-phase, and η-phase. It was found that the thickness of the zinc coating on the surface after plasma cutting is two times less than on the untreated surface, and the reduction in the coating thickness occurs due to a decrease in the ζ-phase thickness. A hypothesis was suggested that the martensite formation on the steel surface leads to the disappearance of the ordered FeSi phase and changes the phase equilibrium in the Fe–Zn–Si system. Consequently, preliminary plasma treatment of the steel surface allows controlling the structure and thickness of the resulting zinc coating and is therefore recommended for introduction into the hot galvanizing process of silicon-containing steels.

Multiscale modeling of cutting processes for TiBw/TA15 composites based on the interface model parameters identification method by microcolumn compression

TiBw/TA15 composites are featured by the network-structured distribution of the reinforced phase quasi-continuously. The multiphase microstructure including the TiB ceramic whisker reinforcement, the titanium alloy matrix and the interface plays a significant role in cutting processes. In this paper, multiscale finite element (FE) cutting models in accordance with the structural characteristics of TiBw/TA15 composites are established. Then, the interfacial mechanical parameters of TiBw/TA15 composites are recognized by the microcolumn compression approach, and the thermoplastic equivalent constitutive parameters (ECP) of the TiBw-rich region in the model are obtained by a two-step FE simulation. The cutting model is validated by orthogonal turning experiments. Finally, the formation of segmented chips can be visualized by the cutting models, which is caused by the compressive stress and the TiB whiskers failure. In addition, the mapping relationship between the critical equivalent strain (CES) and the hardened layer depth (HLD) is established. The results indicate that the HLD reduces with the decrease of cutting speed (VC) and depth of cutting (h). The findings in this paper facilitate a further understanding of the TiBw/TA15 composites cutting mechanism.

Study on the effect of tempering on the impact abrasive wear performance of 45Si2MnCr2Mo ultra-high strength steel

In this paper, three-body impact abrasive wear tests of 45Si2MnCr2Mo ultra-high strength steel (UHSS) at different tempering temperatures were carried out by using the MLD-10 impact abrasive wear machine. The effects of different tempering temperatures on the wear weight loss and the depth of the hardened layer of UHSS were investigated. The results show that the weight reduction rate of the steels tempered at 150 and 220 °C decreases at first and then increases with time, but the steels tempered at 290 and 360 °C gradually increase with time. The surface and subsurface areas of UHSS are strengthened by work hardening after wear. The wear performance of UHSS should consider the change of weight reduction rate with time rather than just considering short-term weight loss. UHSS tempered at 150 °C has the best comprehensive surface hardness, hardening percentage, and effective hardened layer depth, and the wear process is more uniform.

Influence of the time discrepancy (TD) between the first grinding wheel cut-out and the second cut-in of two-pass grinding on the hardened layer

A grind-hardening experiment on nodular cast iron QT400 was done with a surface grinder. The effects of the time discrepancy(TD) between the first cut-out of the grinding wheel and the second cut-in of the two-pass grinding on the grinding force, microstructure, micro-hardness and uniformity of the hardened layer depth were studied. Then, by using the measured tangential grinding force to establish a simulation model of the grinding temperature field. We concluded that increasing TD with the same grinding parameters can reduce micro-hardness and the depth of the hardened layer; indeed, the uniformity of the hardened layer can also be improved. However, the change of TD has no noticeable influence on the grinding force and microstructure of the hardened layer. The simulation results show that with the same grinding parameters, reducing the TD can increase the temperature of the workpiece in the second grinding. The experimental results are consistent with the simulation results, and the relative error of the hardened layer depth is 9%. Under the consistent grinding parameters, when TD = 6 s, the hardened layer depth is moderate and its uniformity is good.

Grinding Burn Detection via Magnetic Barkhausen Noise Analysis Independently of Induction Hardened Depth

The electromagnetic technique based on magnetic Barkhausen noise (MBN) can be used to control the quality of ball screw shafts non-destructively, although identifying any slight grinding burns independently of induction-hardened depth remains a challenge. The capacity to detect slight grinding burns was studied using a set of ball screw shafts manufactured by means of different induction hardening treatments and different grinding conditions (some of them under abnormal conditions for the purpose of generating grinding burns), and MBN measurements were taken in the whole group of ball screw shafts. Additionally, some of them were tested using two different MBN systems in order to better understand the effect of the slight grinding burns, while Vickers microhardness and nanohardness measurements were taken in selected samples. To detect the grinding burns (both slight anddata intense) with varying depths of the hardened layer, a multiparametric analysis of the MBN signal is proposed using the main parameters of the MBN two-peak envelope. At first, the samples are classified into groups depending on their hardened layer depth, estimated using the intensity of the magnetic field measured on the first peak (H1) parameter, and the threshold functions of two parameters (the minimum amplitude between the peaks of the MBN envelope (MIN) and the amplitude of the second peak (P2)) are then determined to detect the slight grinding burns for the different groups.

Effect of carburizing process on bending fatigue performance of notched parts of 18CrNiMo7-6 alloy steel

Since stress concentration is easily formed at the notch, improving the fatigue performance of notched parts is critical. The carburizing process is widely used to manufacture notched parts. In this research, the effects of carburizing process and notch stress concentration on fatigue performance were analyzed by bending fatigue tests. In addition, the microstructure and hardness evolution processes of the carburized notched 18CrNiMo7-6 specimens were observed quasi-in situ. The results showed that macro-plasticity has little effect on the bending fatigue performance of notched samples and that the improvement in fatigue performance is primarily attributable to the high hardness and residual compressive stress introduced by carburizing. The fatigue notch sensitivity is therefore reduced after carburizing. Compared to the uncarburized specimens, the fatigue limit of the carburized specimens is increased by up to 128%. With the increase of the effective hardening layer depth, the fatigue limit increases first and then decreases. Moreover, the brittle phase transformation product (twinning martensite) of metastable retained austenite is easy to produce stress concentration. Conversely, the 'film-like' retained austenite with an extremely high stability can effectively avoid the phase transformation products.

Ultrasonic rolling strengthening effect on the bending fatigue behavior of 12Cr2Ni4A steel gears

An innovative method of ultrasonic rolling strengthening is proposed to process the tooth roots of spur cylindrical gears to improve their bending fatigue life. Variations in the residual stress, surface hardness, and depth of the hardened layer of the tooth root were studied. Subsequently, bending fatigue experiments of a single tooth were performed, and relationships linking residual surface stresses, surface hardness, hardened layer depth, and bending fatigue life were determined. The anti-fatigue mechanism of the ultrasonic rolling gear was clarified: it involves the conversion of tensile residual stresses in the gear tooth roots into residual compressive stresses. After ultrasonic rolling treatment, the bending fatigue strength of gears was increased twice, and their fatigue life was extended by 15 times.

Исследование микротвердости и структуры инструментальных сталей после ионно-плазменного азотирования в тлеющем разряде

In this paper, the effect of ion-plasma nitriding (IPA) on the microhardness and structure of tool steels is investigated. Samples of HSS M2 and P18 steels, quenched at 1300°Cand then tempered three times at 550°C, were used for the study. The IPA was carried out in a gas mixture consisting of 50% argon, 35% nitrogen and 15% hydrogen at a pressure of 250 Pa and a surface temperature of 400°C, 500°C and 600°C for 3h, 6h and 9h, 9 h. It was found that the highest surface hardness of 1600 HV for HSS M2 steel specimens and 1500 HV for P18 steel specimens were observed after IPA in TR at 500°Cfor 9 h. The maximum hardened layer depth of 120 μm for HSS M2 specimen and 100 μm for P18 specimen were observed after treatment at the same temperature for 6 and 9 hours

Possibilities of Using of Surface and Subsurface Waves’ Amplitude-Angle Characteristics for Control of Materials with Surface-Hardened Inhomogeneous Layer

Improving the efficiency of ultrasonic control of hardened surface layers of metal products with a heterogeneous structure obtained using different technologies is a pressing problem of industrial production. The purpose of this work was to investigate the possibilities of measuring the depth of the surface inhomogeneous layer of steel objects on the basis of the use of amplitude and amplitude-angle characteristics of surface and subsurface transverse waves.The analysis of ultrasonic methods of control of physical and mechanical properties of metals by using surface and subsurface waves and experimentally investigated amplitude-angular characteristics of surface waves, the maximum angle of which increases by 3° at change of dimensionless layer depth hλ from zero to0.82. For the first time, the ratio of normalized amplitudes of surface waves taken at certain angles on theamplitude-angle characteristic curve obtained in the echo mode was proposed to be used as correlating parameters with the depth of the hardened layer. As a result of this research, the possibility of using a phased array transducers to solve the above problems.The effect of the hardened layer depth varying from zero to five in the working frequency range of 1.8– 10 MHz on the peculiarities of the refraction effect (including interference) and dependence of the subsurface wave amplitude on the acoustic base has been studied, making it possible to establish conditions that provide for the determination of the hardened layer depth.Circuit solutions have been offered in order to increase the efficiency of control of properties of the surface layers of metal articles on the basis of utilization of small-aperture transducers and ultrasonic reflectors making it possible to form fields of surface waves of different directional pattern.

Study on the Changing Law of Cutting and Ultrasonic Strengthening Surface Integrity during Fatigue of Ti-17 Alloy.

The distribution of surface integrity features directly affects the initiation and propagation of fatigue cracks. In this paper, the surface integrity characteristics changing law of turning and ultrasonic impacting specimens during high cycle fatigue loading has been studied, and the effect of surface modified layer on the fatigue properties of titanium alloy has been revealed. The results showed that the surface roughness increased with the increase of fatigue cycles. The compressive residual stress and its gradient distribution depth decreased continuously. The gradient distribution depth of residual stress in the ultrasonic-impacted surface rapidly decreased by about 50% near the fracture stage. Local cyclic hardening occurred at 20-50 μm from the surface of the specimen in the early stage of fatigue evolution, and then the microhardness continued to decrease. During this process, there were no significant changes in hardened layer depth. The fibrous microstructure of the ultrasonic-impacted surface undergoes a process from coarsening to gradual disintegration during the fatigue process. Its attenuation process needs a longer period of time. The fatigue source of the turned specimen was located at about 320 μm from the surface, and the fatigue source of ultrasonic impact was about 610 μm from the surface. The fatigue striation width of the ultrasonic impact specimen was about 20% narrower than that of the turned specimen. The fatigue life of the ultrasonic impact specimen was increased by 73.9% compared with the turned specimen. The research in this paper is of great significance for exploring the anti-fatigue mechanism and the ability of various surface integrity features.

Effect of ultrasonic surface rolling on microstructural evolution and fretting wear resistance of 20CrMoH steel under different quenching temperatures

The influence of ultrasonic surface rolling (USR) treatment on microstructures, residual stress, microhardness and fretting wear behaviors of 20CrMoH steel under different quenching temperatures (740, 840 and 940 °C) was systematically investigated. The results indicated that the maximum hardening layer depth of the USR treated specimen quenched at 740 °C was about 130 μm, accompanied by grain refinement and high-density dislocations. Simultaneously, the microhardness was mostly increased by 212 HV0.2 and the highest surface residual compressive stress (RCS) was up to −649 MPa. The fretting wear mechanisms of the specimens in different treatment states were mainly delamination and oxidative wear. The volume wear loss of the USR treated specimen quenched at 940 °C was reduced by 48% compared with the untreated specimen quenched at 740 °C. This could be benefited from the protection of the oxide layer and the effective prevention of cracks source by the higher surface RCS, as well as the grain refinement and the increase in dislocations caused by USR treatment.

The Impact of Prenitriding on the Microstructure and Mechanical Properties of the Carburized Surface Layer in a Martensitic Stainless Steel

Herein, it is proposed to obtain a favorable combination of microstructure and mechanical properties of martensitic stainless steel 14Cr14Co13Mo5 by prenitriding method before carburizing and appropriate heat treatment processes. The result indicates that the effective hardened layer depth is increased by 32% to 0.66 mm, and the hardness is significantly improved by prenitriding. The confocal laser scanning microscope and electron backscattered diffraction show that the prenitriding can effectively refine the martensite substructure of the carburized layer after quenching due to the refinement of prior austenite grain. In addition, plenty of second‐phase particles M2N with finer size appear at the same case layer depth instead of coarse M23C6 in the specimen prenitrided, which optimize the microstructure of the case layer.

Combining the Finite Element Analysis and Kriging Model for Study on Laser Surface Hardening Parameters of Pitch Bearing Raceway.

Laser surface hardening is used to improve the fatigue performance of the large diameter pitch bearing. Determination of the process parameters by a trial and error method, depending on the experience of the technician, by changing the parameters repeatedly for each laser surface hardening process is time-consuming and costly. In this paper, a method of analyzing the maximum temperature and depth of a hardened layer during the laser surface hardening process for a pitch bearing raceway of a wind turbine is proposed, which combines finite element simulation and the Kriging model. A three-dimensional finite element model of a pitch bearing ring was established using ABAQUS. The temperature field analysis was performed. The effects of process parameters including laser power, scanning speed, and laser spot radius on the depth of the hardening layer were investigated. Then, taking into account the interactional effects of different process parameters, Kriging models were constructed to reflect the relationship between input process parameters and output responses. The results show that the Kriging approximation model has a small relative error compared with the simulated results and can be used to predict the hardened layer depth.

Effect of ultrasonic surface rolling process on the surface properties of QAl10-3-1.5 aluminum bronze alloy

The main purpose of this article is to study the effect of ultrasonic surface rolling process (USRP) on the surface properties of QAl10-3-1.5 aluminum bronze alloy under different rolling reduction and rolling times, providing ideas for improving the poor wear resistance of valve stem nuts and sealing rings. SEM, EDS and optical three-dimensional profiler were used to characterize the microstructure characteristics of the surface modified layer and the surface morphology of the wear traces. The results show that the surface layer of the USRPed sample has undergone severe plastic deformation. The α phase is elongated, and the microstructure structure shows a fine and uniform distribution state. And the grain size of α phases decreased, and the number density of β phases increased. Compared with the untreated sample (only cutting and polishing), the surface roughness of the USRPed sample reaches nearly Ra 0.04 μm; the maximum surface micro-hardness is 323.04 HV, increasing by 75%; the maximum depth of surface hardening layer is about 570 μm. The friction coefficient, wear mass loss and the width and depth of the wear traces of the USRPed samples are significantly reduced, while the wear resistance is significantly enhanced. By comparing the surface wear morphology of the samples under different process parameters, it is found that the main wear mechanism of the untreated samples is adhesive wear, while the main wear mechanism of the USRPed samples is abrasive wear. The improvement in wear resistance is attributed to the refined and homogenized surface microstructure, the smaller surface roughness, the larger surface micro-hardness and surface hardness layer depth after USRP.

Machining-Induced Work Hardening Behavior of Inconel 718 Considering Edge Geometries

As a representative type of superalloy, Inconel 718 is widely employed in aerospace, marine and nuclear industries. The significant work hardening behavior of Inconel 718 can improve the service performance of components; nevertheless, it cause extreme difficulty in machining. This paper aims to investigate the influence of chamfered edge parameters on work hardening in orthogonal cutting of Inconel 718 based on a novel hybrid method, which integrates Coupled Eulerian-Lagrangian (CEL) method and grain-size-based functions considering the influence of grain size on microhardness. Orthogonal cutting experiments and nanoindentation tests are conducted to validate the effectiveness of the proposed method. The predicted results are highly consistent with the experimental results. The depth of work hardening layer increases with increasing chamfer angle and chamfer width, also with increasing feed rate (the uncut chip thickness). However, the maximum microhardness on the machined surface does not exhibit a significant difference. The proposed method can provide theoretical guidance for the optimization of cutting parameters and improvement of the work hardening.

Impact of Magnetic-Pulse and Chemical-Thermal Treatment on Alloyed Steels’ Surface Layer

The relevant problem is searching for up-to-date methods to improve tools and machine parts’ performance due to the hardening of surface layers. This article shows that, after the magnetic-pulse treatment of bearing steel Cr15, its surface microhardness was increased by 40–50% compared to baseline. In this case, the depth of the hardened layer was 0.08–0.1 mm. The magnetic-pulse processing of hard alloys reduces the coefficient of microhardness variation from 0.13 to 0.06. A decrease in the coefficient of variation of wear resistance from 0.48 to 0.27 indicates the increased stability of physical and mechanical properties. The nitriding of alloy steels was accelerated 10-fold that of traditional gas upon receipt of the hardened layer depth of 0.3–0.5 mm. As a result, the surface hardness was increased to 12.7 GPa. Boriding in the nano-dispersed powder was accelerated 2–3-fold compared to existing technologies while ensuring surface hardness up to 21–23 GPa with a boride layer thickness of up to 0.073 mm. Experimental data showed that the cutting tool equipped with inserts from WC92Co8 and WC79TiC15 has a resistance relative to the untreated WC92Co8 higher by 183% and WC85TiC6Co9—than 200%. Depending on alloy steel, nitriding allowed us to raise wear resistance by 120–177%, boriding—by 180–340%, and magneto-pulse treatment—by more than 183–200%.