High Compressive Residual Stress Research Articles

Enhanced Durability of Wood Cutting Tools through Thermal Cycling.

This study investigates the impact of multi-step austenitization heat treatment on the in-service life of modified AISI A8 cold work tool steel knives used in wood cutting. The knives were subjected to two treatment methods: single quenching and double tempering (SQDT) and double quenching and double tempering (DQDT). Both treatments were followed by physical vapor deposition (PVD) coating to enhance surface properties. The DQDT treatment resulted in a finer microstructure and more uniform carbide distribution. Field tests on 24 knives over 124 h demonstrated up to 130% improvement in wear resistance for DQDT knives, along with superior edge stability and better PVD coating preservation. DQDT knives exhibited ductile fractures characterized by dimples, contrasting with the brittle fracture and cleavage facets in SQDT knives. Residual stress measurements showed higher compressive stresses in DQDT knives (-280 MPa) compared to SQDT knives (-30 MPa), which increased further after field testing. The enhanced performance of DQDT knives is attributed to their refined microstructure, improved carbide distribution, and higher compressive residual stresses, offering significant potential for improving wood cutting tool efficiency and durability.

Surface fatigue characterization and its enhancement by the engineered ultrasonic rolling process for 300 M ultrahigh strength steel

The fatigue life of surface layer (FSL) is innovatively characterized to accurately capture the effect of surface integrity on the fatigue behavior of the components. The sensitivity of FSL of 300 M ultrahigh strength steel to the surface integrity indexes induced by representative manufacturing processes was analyzed by analytical modeling and fatigue tests from the perspective of engineering fracture mechanics. The ultrasonic surface rolling process (USRP) was introduced to optimize the fatigue limit of 300 M steel, and the improvement in fatigue life was experimentally quantified. Besides, the fracture analysis was conducted to provide the reason why USRP can enhance the fatigue behavior of 300 M steel. The results show that FSL occupies a majority with percentage of over 95 % in the entire fatigue life and a strong relation with the machined surface defects, especially the surface machining marks. The excellent surface finishing effect and high compressive residual stresses induced by engineered USRP could transfer the crack source from surface machining marks into subsurface inclusions, which greatly prolongs the fatigue crack initiation life and thereby the entire fatigue life. To be specific, the fatigue life was elevated by more than 40 times and the fatigue strength was increased by 34.7 % after USRP for the tested 300 M steel.

Enhanced adhesion and wear resistance of DLC films on AZ31 alloy achieved with high bias voltage

Diamond-like carbon (DLC) films exhibiting high adhesion and exceptional wear resistance were successfully applied onto the AZ31 surface without a adhesive layer. The structural features of the film were examined utilizing Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Raman spectroscopy. Mechanical properties were evaluated through Nano-indentation testing, while adhesion was evaluated using a scratch tester. Residual stress was determined by Stoney's equation. The results indicate that utilizing a high substrate bias ranging from −500 to −800 V, results in the presence of multiple craters and dislocations, which contribute to the enhancement of high residual compressive stress and hardness in the DLC film. The heightened compressive stress effectively embeds carbon atoms into the surface of the soft AZ31, creating an interfacial layer that significantly improves adhesion and wear resistance of the film. In contrast, at moderate bias levels with a range from −300 to −500 V, an increase in substrate temperature leads to the expansion and discontinuation of adjacent layers that decreases the mechanical properties, adhesion, and wear resistance of the film. When at low bias levels between 0 and -300 V, the hardness, crack resistance, residual stress, and wear resistance all increase with increasing of bias. Additionally, in this work, the mechanisms of adhesion and wear for the biased film are analyzed.

Rapid carburizing of low-alloy steel by atmospheric-controlled induction-heating fine-particle peening and investigation of its fatigue properties

Atmospheric-controlled induction-heating fine-particle peening (AIH-FPP) was applied to low-alloy, low-carbon steel AISI 4120 to achieve rapid carburizing within minutes and enhance fatigue strength. The shot particles used during AIH-FPP were specifically created by mechanically milling a mixture of steel particles and carbon powders. The specimens were analyzed using laser microscopy, optical microscopy, X-ray diffraction for residual stress measurement, a micro-Vickers hardness tester, and an electron probe micro-analyzer. Axial fatigue tests and fracture surface analyses via scanning electron microscopy and energy-dispersive X-ray spectroscopy were also conducted. AIH-FPP effectively transferred carbon to the treated surface and facilitated its diffusion in a short period, creating a martensite layer with high hardness and compressive residual stress, which resulted in increased fatigue strength. The fatigue strength of the AIH-FPP-treated specimens was influenced by the conditions of reheating and quenching, which altered the prior austenitic grain size and stress concentration at the specimen surface. Notably, specimens treated with AIH-FPP followed by reheating and water-injection quenching exhibited fatigue strength comparable to that of conventional gas-carburized specimens, owing to the formation of a carburized layer with a small prior austenite grain size.

Enhanced hot corrosion resistance of AlCoCrFeNi2.1 high entropy alloy coatings by extreme high-speed laser cladding

Extreme high-speed laser cladding (EHLC) and multiple laser remelting (EHLC-MR) are used to improve hot corrosion resistance of AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) coatings by refining their microstructures, introducing low angle grain boundaries (LAGBs) and high densities of dislocations as well as higher compressive residual stresses (CRSs) in the coatings. The experimental results show that finer microstructure, more LAGBs and high densities of dislocations are beneficial to increase Al2O3 nucleation sites and promote the uniform formation of the oxide layer on the coating surface. On the other hand, higher CRSs suppress the initiation and propagation of cracks as well as enhance the adhesion between the oxide layer and the substrate. Thus the hot corrosion resistance of the EHEA coatings under a molten salt of 75% Na2SO4 + 25% NaCl at 900°C is improved significantly. These novel results provide effective approach for designing elevated-temperature materials.

Microstructure and mechanical properties of wire and arc additive manufactured 2319 aluminum alloy treated by laser shock peening

The components manufactured by Wire and Arc Additive Manufacturing (WAAM) have some problems to be solved urgently, such as uneven microstructure, numerous pore defects, and residual tensile stress. Laser Shock Peening (LSP) is an innovative and advanced surface modification technology that improves mechanical characteristics by inducing significant plastic deformation and high compressive residual stress on metal surfaces. Therefore, combining LSP with WAAM is expected to solve its existing problems. In this work, LSP with different energy parameters was used to post-process the WAAM 2319 aluminum alloy. The results indicated that LSP could improve the microstructure, eliminate near-surface pores, harden the surface layer, and induce a residual compressive stress layer, and the effect was more effective with the increase of laser energy applied. The yield strength of the peened specimens significantly increased by 60.73 %, and the ultimate tensile strength also increased by 16.03 %. The hole fatigue life of the peened specimens was significantly improved, increasing by 179.8 % and 261.7 %, respectively, applying laser energies of 5 J and 10 J. Therefore, the engineering industry may benefit from a combination of LSP and WAAM technology.

Probing fretting wear behavior of gauge-changeable spline axle under rotational bending loads

The latest generation of gauge-changeable trains in China feature designs with their wheels and axles connected by spline couples and cylindrical fits. In comparison to the interference fitted wheelset, the spline axle with clearance fit is more prone to fretting damage. In this study, the stress distribution of spline axle was analyzed using finite element method. Then, a rotatory bending test on scaled wheel/axle samples was conducted to reveal the fretting wear behavior of the gauge-changeable axle. During traction, the contact stress of the spline peaks at 311 MPa on the tooth’s root side, with a corresponding relative slip of 14 μm. Fretting wear is observed in the spline axle, the damage zone of the wheel seat can be categorized into five bands (A–E), and severely damaged areas are covered with red-brown debris. Moreover, the main damage mechanism of untreated spline axle and surface-modified spline axle is delamination accompanied with oxidation. The improved properties of plasma nitriding and grease lubricant are attributed to the high surface hardness and residual compressive stress, as well as low frictional stress.

Study on the effects of bilateral laser-assisted cutting on surface integrity and fatigue life of FeCoCrNiAl0.6 alloy

This study investigates the impact of various cutting parameters in both unilateral and bilateral laser-assisted cutting processes on the surface integrity and fatigue life of FeCoCrNiAl0.6 high-entropy alloy. By utilizing ABAQUS/FE-SAFE simulations and conducting laser-assisted cutting and fatigue tensile tests, differences in surface quality and fatigue life cycles of FeCoCrNiAl0.6 alloy samples under different cutting scenarios were evaluated. The results indicate that in high-speed laser-assisted cutting, an increase in laser speed leads to a progressive decline in surface quality for both unilateral and bilateral methods. Nevertheless, at a laser speed of 4000 mm/s, optimal surface quality is achieved in both approaches, with the bilateral method consistently providing superior results across varying speeds. Regarding residual stress, unilateral laser-assisted cutting at 4000 mm/s produces a surface residual compressive stress of 532 MPa, which is twice as high as that observed at 10000 mm/s. The bilateral method shows a symmetric distribution of residual compressive stress, with peak values of 567 MPa and 528 MPa on the front and back surfaces, respectively. In terms of fatigue life, bilateral laser-assisted cutting demonstrates enhanced performance at 4000 mm/s, achieving a fatigue life cycle that is 4.72 times longer than that of the unilateral method. Overall, bilateral laser-assisted cutting improves the fatigue life of the material through symmetric thermal effects and higher residual compressive stress, particularly at lower laser speeds and optimal cutting depths.

Effect of the conventional shot peening and multiple shot peening on microstructure and residual stress of TC17 titanium alloy

This study examines the residual stress, microstructure, and stress-induced phase transformation of TC17 titanium alloy after different shot peening processes. A comprehensive analysis of the unique impact of shot peening on α-Ti and β-Ti was performed. The results indicate a substantial reduction in the grain size of the deformed layer and the creation of a high density of dislocations. Additionally, increased peening intensity results in decreased grain size, and multiple shot peening promotes further reduction in grain size. Compressive residual stresses were detected in the deformed layer, and multiple shot peening significantly augmented the residual stresses in the surface and near-surface regions. In particular, the highest compressive residual stresses after triple shot peening treatments were measured at −1079 MPa (at a depth of 10 μm for α-Ti) and −792 MPa (at a depth of 50 μm for β-Ti). In addition, multiple shot peening can significantly reduce surface roughness and enhance surface nanocrystallization when approximate surface residual stresses are obtained. Remarkably, the use of single shot peening revealed parallel stacking faults in certain α-Ti samples. However, under multiple shot peening, these stacking faults evolved into face-centered cubic Ti (FCC-Ti) with broader widths and a greater number. The stress-induced phase transition orientation relation was determined to be (0001)HCP//(11¯1)FCC and [21¯1¯0]HCP//[011]FCC, with α-Ti grains being interspersed with FCC-Ti, thus promoting additional grain refinement.

Estimating the fatigue limits for quenched and tempered steel rods treated with multifunction cavitation considering residual stress, hardness, and surface pits

AbstractIn this study, multifunction cavitation (MFC) was performed on low‐alloy steel (AISI 4140 steel) rods with different hardnesses to increase their fatigue limit. It was found that a high compressive residual stress was generated on the surface of steel rods by MFC and that the magnitude of the compressive residual stress tended to increase with increasing specimen hardness, which resulted in a higher fatigue limit. However, fatigue cracks are known to be initiated from the pits and red rust that form on the surface during MFC treatment in water. Furthermore, relaxation of the compressive residual stress was also investigated during the fatigue test to elucidate the mechanism for improving the fatigue properties. The results showed that the fatigue limit for MFC‐treated steel rods was accurately estimated by considering residual stress relaxation, hardness, and pit formation. Validation of the fatigue limit estimation was also conducted through comparison with Murakami's equation.

Laser treatment of (Zr-Ta-W-Ti)C-SiC based high entropy carbide ceramics reinforced with carbon nanotubes, graphite and graphene nanoplatelets

This study investigates the effect of laser surface treatment on spark plasma sintered (Zr-Ta-W-Ti)C-SiC (ZTaWT-S) based high entropy ceramic (HEC) composites, reinforced with multiwalled carbon nanotubes (CNT) (ZTaWT-SC), graphite (ZTaWT-SG), and graphene nanoplatelets (GNP) (ZTaWT-SGNP). The increased hardness of the laser-treated composites (25–33 GPa) when compared to that of untreated composites (23–28 GPa) is attributed to the high compressive residual stresses, ranging from 1400 to 2900 MPa. The laser-treated ZTaWT-SGNP composite exhibited a minimum scratch wear rate of ∼0.9 × 10−1 mm3/N.m, representing a 57 % and 73 % reduction compared to the untreated ZTaWT-SGNP and the laser-treated ZTaWT-S, respectively. ZTaWT-SGNP composite demonstrated the best resistance to damage accumulation, due to the synergistic effects of laser treatment and GNP reinforcement, enhancing its suitability for extreme environments.

The synergistic effect of gradient nanostructure and residual stress induced by expansion deformation on the tension-tension fatigue performance of Ti6Al4V holes

A large number of titanium alloy structural components in aircraft are joined and assembled through holes. The complex service conditions pose high requirements for the fatigue performance of the holes. The study aims to use expansion deformation to induced gradient nanostructures and residual stress enhance the fatigue performance of Ti6Al4V holes. By studying the evolution process of the microstructure in titanium alloys, the formation mechanism of gradient nanostructures has been obtained, and their impact on various stages of fatigue fracture is analyzed. The results showed that the split sleeve cold expansion (CE) process caused severe plastic deformation on the surface of the hole, resulting in a large amount of LAB production and a transformation of the main texture components. Meanwhile, the gradient nanostructures are formed on the hole surface, which include nanocrystalline layer, superfine lath grain layer, lath grain layer and severe deformation layer. During the expansion deformation process, the slip of dislocations leads to the formation of high-density dislocation structures, which evolve into subgrain boundaries and then undergo dynamic recrystallization through subgrain rotation to achieve grain refinement. What's more, the degree of grain refinement, depth of gradient nanostructure, and residual stress increase as the expansion deformation intensifies. The depth of gradient nanostructure is 300 μm, and the maximum residual stress is −419 MPa, when the deformation is 5 %. The combined effect of gradient nanostructures and high residual compressive stress induced by expansion deformation has increased the total fatigue life and crack propagation life of CE-5 specimen by 2.9 and 3.4 times compared to NCE specimen. This work provides an effective method and theoretical analysis for improving the fatigue life of titanium alloy holes.

Effect of grit blasting on fatigue behavior of 2024-T3 aero Al alloy

Aiming at the removal of native oxide film on 2024-T3 Al alloy before plasma electrolytic oxidation, the methods to reduce the fatigue damage caused by grit blasting are explored. Effects of the grit size and pressure on surface roughness, residual compressive stress (RCS), and fatigue life of the Al alloy are studied. Increasing grit size and pressure leads to the increase in the surface roughness and RCS. Based on the theorem of momentum and tool cutting principle, mechanism of the grits on the craters and RCS is revealed. It is found that the angularness of the small-sized grit results in the formation of long scratches. The grit with high kinetic energy induces the large craters and high RCS. The craters are the primary fatigue crack initiation source. Moreover, the craters with long scratch and large height lead to the premature fatigue failure of the grit blasted specimens. However, Fatigue behavior is insignificantly affected by the RCS. The results provide new insights into the fatigue deterioration mechanism and life optimization of the grit blasted samples. Consequently, a parameter optimization scheme for the fatigue life of the grit blasted Al alloy is proposed.

Numerical simulation study of combined shot peening and laser shock peening on surface integrity of Ti-6Al-4V titanium alloy

Combined shot peening and laser shock peening (CSP) can introduce high surface compressive residual stress (CRS) and deep CRS layer, and reduce the high surface roughness caused by shot peening. The relationship between CSP sequences and surface integrity, including CRS and surface roughness, is far from satisfying the actual demand. In this paper, we construct a finite element model considering initial surface profile features. The experimental results agree with the simulated results. Based on the simulation results, axial and longitudinal stress wave transfer effects on surface CRS and depth CRS are investigated. Compared with shot peening (SP) and laser shock peening (LSP) alone, CSP treatment can increase CRS depth and CRS magnitude by 1060 μm and 50 ∼ 80Mpa, respectively. In addition, the roughness following CSP treatment is lower than that observed after SP treatment alone, and the roughness varies depending on the sequence of CSP treatment. Specifically, the roughness values for SP, SP + LSP, and LSP + SP are 0.938 ± 0.031 μm, 0.982 ± 0.11 μm, and 1.168 ± 0.093 μm, respectively. The surface morphology, hardness, and simulation results are combined to reveal the reasons for the reduction of surface roughness after CSP treatment. The changes of peaks and valleys after CSP treatment compared with single SP treatment were studied, and the variation trend of surface roughness was further explained.

Prediction of residual stress depth profiles in case-carburized gears

Residual stresses have a significant influence on the load carrying capacity of gears. High near-surface compressive residual stresses can increase pitting strength and tooth root bending strength up to 50%. Tooth flank fracture (TFF) is a gear fatigue failure mode, which is in contrast to pitting or tooth root breakage not initiated at the surface or close to the surface but in larger material depths beneath the active gear flank. Therefore, the residual stresses in larger material depths are decisive for TFF. In these larger material depths, the residual stress conditions are almost unknown up to now. It is assumed that tensile residual stresses are present in these areas, which can negatively influence the TFF load carrying capacity. So far, no validated methods are known to estimate or predict these tensile residual stresses. As a result, the tensile residual stresses could not be considered in the calculation methods for the risk of TFF at all until recently.This paper presents a method to predict the residual stresses in case-carburized gears based on comprehensive numerical simulations of case-carburizing processes of different-sized gears. The calculated residual stress profiles also consider the tensile residual stresses in larger material depths.

Residual stress depth profiles self-developed in cathodic arc deposited Ti-Al-N coatings prepared at different constant substrate bias values

Ti-Al-N coatings were prepared by cathodic arc deposition on Inconel 718 substrates at different values of constant substrate bias voltage, aiming to produce samples with different self-developed residual stress (RS) depth profiles through the thickness of the coatings. RS profile measurements and structural characterization were performed on a laboratory-scale x-ray diffraction system (x-ray energy of 8 keV) and in a synchrotron x-ray radiation facility (x-ray energy of 15 keV). Mechanical testing to obtain hardness and Young’s modulus values was performed by instrumented nanoindentation. The results indicate higher compressive RS at the film/substrate interface that decays to lower compressive stress or mild tensile stress at the film surface. Surface hardness and the compressive RS value of the coating increase with larger values of the substrate bias voltage. By comparing the stress characterization done on a laboratory scale and at the synchrotron facility, one observes a generally good agreement, indicating that these analyses may be conducted at a smaller scale and with less costly equipment, and still maintain a reliable precision. The work presents and reviews in detail the methodology of the RS depth-profile analysis. The highest hardness of 31.1 GPa and near-substrate compressive RS around −10 GPa were obtained for a bias of −100 V. Transmission electron microscopy results indicate that regions with higher compressive stresses are found to have smaller columns and denser structure, while portions of the same sample with mild compressive or tensile stresses present larger column size and are richer in hexagonal phases. The findings demonstrate the complex interplay between stress, microstructure, and ultimately mechanical properties in industrially produced Ti-Al-N coatings and indicate that any successful strategy to mitigate stress development should consider the inhomogeneous self-developed stress gradients present even in coatings deposited under constant and controlled conditions.

Machinability of extruded H13 tool steel: Effect of cutting parameters on cutting forces, surface roughness, microstructure, and residual stresses

The production of H13 tool steel (TS) by material extrusion (MEX) is a promising method in various applications, but as-built surface roughness does not comply with the quality requirements. Hence, this study investigated the effects of cutting parameters on tool wear, cutting forces, surface quality, microhardness, structure, and residual stresses when machining H13 TS produced by MEX. Dry machining (DM) proved advantageous in certain indicators such as tool wear and cutting forces in comparison to the flood cooling (FC). The lowest surface roughness (0.08 µm) was achieved at the cutting speed of 80 m/min, feed per tooth of 0.005 mm, and FC which corresponded to a 41 % decrease compared to DM under same conditions. Surface microhardness increased by 20 % after machining, decreasing with distance from the surface. The highest compressive residual stresses were observed under FC, while the DM resulted in a 78.2 % decrease in residual stresses due to a partial annealing effect caused by higher surface temperature. Overall, DM exhibited great potential for achieving high-quality surfaces with a favorable structure and residual stresses. This study´s novelty and robustness lie in its significant contribution to practical industrial applications, such as mold and core production.

Microstructure, corrosion resistance and wear properties of laser directed energy deposited CrCoNi medium-entropy alloy after cyclic deep cryogenic treatment

ABSTRACT Subjected to repeated heating and cooling, laser directed energy deposited (LDED) parts always possess considerable residual stress, which severely limits their industrial applications. In this work, cyclic deep cryogenic treatment (CDCT) was performed to finely tune the residual stress and microstructure of LDED-fabricated CrCoNi medium-entropy alloy (MEA). With increasing number of CDCT cycles, crystalline defects within the sample became denser due to the repeated visco-plastic deformation. The compressive residual stress (CRS) of the sample was estimated to be 361.9 ± 16.8 MPa after 30 cycles of CDCT, 64.2% higher than that in the as-built condition. Due to the existence of dense crystalline defects and high CRS, the corrosion and wear rates of CDCT-treated CrCoNi MEA were significantly decreased compared with the as-built condition. This work demonstrated CDCT as an effective means for regulating the residual stress, microstructure, and surface performance of LDED-fabricated MEA.

Surface integrity and corrosion resistance of 18CrNiMo7-6 gear steel subjected to combined carburized treatment and wet shot peening

Typically, a cost-effective and versatile carburizing process is used to improve the surface integrity of high-value-added gear components. In this study, carburized treatment and wet shot peening (WSP) were applied to increase the corrosion resistance of 18CrNiMo7-6 gear steel. The surface integrity and corrosion resistance after carburizing and combined treatment (carburized treatment + WSP) were analyzed. The results indicated that the combined treatment converted the retained austenite surface layer within approximately 45 μm from the surface into the martensitic phase, with a 13.9 % reduction in equivalent grain size and a 23.6 % increase in dislocation density compared with carburizing. Furthermore, electrochemical experiments in a 3.5 wt% NaCl solution indicated that the combined treatment process increased the corrosion resistance compared with carburizing (55.4 % lower corrosion current density and a higher Fe2+/Fe3+ ratio). Despite the high surface roughness obtained with combined treatment, the improved corrosion resistance is primarily ascribed to the high compressive residual stress and dislocation density. This study provides insights into the surface strengthening design of 18CrNiMo7-6 gear steel for corrosive environments—particularly the synergistic strengthening effect of carburizing and WSP.

Investigation of the Machined Surface Integrity of WC-High-Entropy Alloy Cemented Carbide

A fine-grained WC-15wt%Al0.5CoCrFeNi cemented carbide was prepared through a vacuum and gas pressure sintering. For achieving high surface integrity, diamond wheel grinding serves as the primary molding process for the machining of WC cemented carbide. To reveal the influence of grinding on the surface integrity of fine-grained WC-HEA cemented carbide, studies were conducted on grinding force, surface microstructure, surface roughness, residual stress, microhardness, and bending strength. The morphological analysis of the ground surface indicated a transition in the material removal mechanism of WC-HEA cemented carbide from ductile removal to brittle removal, with brittle removal becoming predominant as the depth of grinding increases. With the increasing depth of grinding, the grinding force increases, and the grinding force increases while the surface roughness decreases. Correspondingly, there is an improvement in both hardness and bending strength. Additionally, grinding induces high residual compressive stress on the surface, with a maximum compressive stress of 1795 MPa. The bending strength of the material is found to be dependent on the residual stress.