Surface Mechanical Treatment Research Articles

Modified Mechanical Surface Treatment for Optimized Fatigue Performance of Martensitic Stainless Steel AISI 420

Mechanical surface treatments, deep rolling or shot peening can enhance the fatigue performance of metallic materials because near-surface compressive residual stresses and work hardening states can inhibit or retard crack initiation and propagation. Thus, the stability of compressive residual stresses and work hardening states during fatigue is very important. However, generated compressive residual stresses and work hardening layers can be relaxed because of dislocation movements, rearrangements and annihilations. The strain ageing concept is one of the ways to pin or obstruct dislocations by solute atoms (called the Cottrell cloud) as a consequence of high stability of near-surface residual stresses and work hardening states. In this research, the conventional deep rolling and its modifications, high temperature deep rolling and deep rolling followed by appropriate annealing were performed on martensitic stainless steel AISI 420. Fatigue tests were performed using a rotary bending fatigue machine to evaluate fatigue performance as well as the strain ageing effects. It was found that the conventional deep rolling could enhance the fatigue performance through generated compressive residual stresses and work hardening layers at the surface, and near-surface regions. The modified deep rolled (high temperature deep rolling and deep rolling followed by annealing) conditions exhibited a greater fatigue lifetime and performance than those of the conventional deep rolling, although some residual stress and work hardening relaxations were observed after the modified deep rolling processes.

Corrosion Resistance of 316L Biomaterial in Simulated Body Fluid by Modification of Shot Distance and Shot Angle of Shot Peening

Corrosion resistance of 316L biomaterial can be improved by mechanical surface treatment such as shot peening. Shot peening can create plastic deformation as a nanocrystal surface layer on the metal surface to protect the material from corrosion attack. This study aims to investigate the effect of shot peening on the corrosion resistance of 316L to reach the best rate of corrosion. The shot peening parameters in this research are shot distance (6, 8, 10, and 12 cm), shot angle (30, 60, and 90°), compressor pressure (7 kg/cm2), shot duration (20 minutes), and steel balls S-170 (diameter of 0.6 mm). Simulated Body Fluid (SBF) was used as a corrosion media with ion concentrations nearly equal to human blood plasma. Corrosion tests were used versaSTAT, and the data were analyzed by VersaStudio. The result shows that the shot peening can decrease the corrosion rate of the 316L biomaterial. The larger the shot angle, the lower the corrosion rate and the nearer the shot distance, the lower the corrosion rate. The nearest shot distance (6 cm) and the largest shot angle (90°) give the best result to decrease the corrosion rate from 0.8617 mpy to 0.1096 mpy.

Structure and Lattice Strains in the Surface Сr–Mn–N Steel Layer Formed by a Combination of Friction and Electron-Beam Treatments

The effect of surface mechanical and heat treatment, which includes successive friction and electron-beam treatments, on the structure, mechanical properties, and the elastically deformed state of a 16.5 Cr–18.8 Mn–0.53 N–0.07 C steel has been studied in this work. The mechanical and heat treatment has been shown to refine the grain structure in the surface layer to a grain size of 2 μm, form a {100} 〈001〉 texture, and retain a deformation-hardened sublayer. A surface layer to 200 nm thick is enriched with oxygen, nitrogen, and carbon. X-ray diffraction has been used to study austenite lattice strains caused by residual stresses. The mechanical and heat treatment has been found to reduce the friction-induced elastic lattice contraction along the normal to the surface. The direction [100] is most sensitive to the effect of residual stresses and can serve as a marker when analyzing the nature of residual stresses in steels with structurally-changed plastically-undeformed surface layers.

Analysis of surface treatment of ASTM A516 Grade 70 using Salt spray method

Conversion coating is an effective way to safeguard against corrosion. It is performed on a number of materials inhibiting the surface layer to corrosive attack. In this work surface engineering is carried out on test material ASTM A 516 Grade 70 which is widely used for constructional purposes. During the passivation process samples were given a hot alkaline oxide bath in sodium hydroxide and sodium nitrate. The corrosion resistance was then analyzed using advanced testing procedures. Salt spray test was used as a yard stick in making a comparative analysis of different samples including unpassivated samples, passivated samples and passivated samples with prior surface treatment. Results have shown that mechanical surface treatment improves material life by 3% whereas passivation with prior surface treatment can increase life by 18%.

Mechanical properties of AA6061 aluminium alloy subjected to severe surface mechanical treatment

The improvement in the mechanical properties of AA6061-T651 alloy induced by Severe Surface Mechanical Treatment (SSMT) process was studied. The effects of the process parameters, namely, speed of revolution (N), size of shots (D) and treatment time (T) on hardness, ultimate tensile strength and surface roughness were identified. These parameters are directly related to the energy input essential to induce large strains, grain refinement and accumulation of dislocations that result with a consequent increase in the strength of the alloy. This has implications for structural applications. The study has revealed that peening with shots of larger diameter are preferable to using smaller ones because then the hardness and ultimate tensile strength (UTS) increase by about 20%–30%, when the alloy is in T651 condition ( in R&D it is stated T6). Further, the average deformed layer thickness of about 450 μm has been observed. But the use of such larger diameter balls gives rise to high surface roughness. A careful trade-off between these two counteracting effects could make SSMT a viable process for increasing the specific strength and reducing the cross-section of load carrying members.

Study on the influence of process parameters of severe surface mechanical treatment process on the surface properties of AA7075 T651 using TOPSIS and Taguchi analysis

This article investigate the mechanical and wear characteristics of AA 7075 T651 alloy subjected to severe surface mechanical treatments(SSMT). The Taguchi orthogonal array and Analysis of variance are employed in identifying the influence of process parameters and their significant contribution. A Multi-criteria decision making process is adopted to identify the ideal condition for characterization analysis. The optimal value ascertained is the usage of shot diameter of 8 mm, 60 min of treatment duration and speed of revolution at 1000 rpm. It is identified that the shot diameter is the major contributing factor in improving the wear and hardness of the specimen. A maximum hardness of 235 HV is obtained with an average deformed layer thickness of 350 μm in the optimal condition. Further, the ultimate tensile strength value of 637 MPa and wear rate of 2.77 × 10–6 g m−1 is observed. The x-ray diffraction (XRD) analysis divulged an increment of 83.22% in the compressive residual stress introduced during the treatment with SSMT process. This abate corrosion rate by 17.77%. The enhancement in the wear and corrosion resistance is ascribed to the introduction of compressive residual stress and dislocation strengthening during SSMT process

Surface mechanical attrition treatment of commercially cold rolled copper plate

Severe plastic deformation such as surface mechanical attrition treatment (SMAT) transfers surface layer of metallic material into ultra-fine-grain. In this work commercially cold rolled copper plate subjected to SMAT for different time 10, 20, 30, 60 and 120 min. Significant variation of crystallite size, lattice strain and stored energy along different crystallographic planes was estimated from X-ray diffraction (XRD) with initial orientation during the SMAT process. Through the SMAT process stored energy increased while lattice parameter decreases with treatment time. The corrosion behavior of SMAT copper were comparatively investigated by electrochemical methods in 5 wt% NaCl solution. Mechanical surface treatment processes have a great influence on the surface which increase surface activities consequently improve the corrosion resistance of metal. SMAT process enhance the corrosion resistance of copper surface resulting from oxide layer growth at the treated surface. Higher impedance and lower corrosion current were observed after SMAT. The hardness (Hv) increased with increasing SMAT time and tends to be stable after 30 min of treatment. The hardness and corrosion rate values were strongly related to the samples crystallographic planes orientation.

A Comprehensive Numerical Approach for Analyzing the Residual Stresses in AISI 301LN Stainless Steel Induced by Shot Peening.

Shot peening is one of the most famous mechanical surface treatments to improve fatigue performance of metallic components, which is attributed to high amplitude compressive residual stresses. A numerical approach is developed to analyze the residual stresses in 301LN metastable austenitic stainless steel by shot peening. The material behavior is described by a proposed constitutive model in which strain-induced martensitic transformation, isotropic hardening and kinematic hardening effects are taken into account properly. Both single shot and random multiple shots peening were simulated and analyzed. A numerical method is presented with the Python programming language to make the multiple shots follow a random probability distribution. Results demonstrate that the simulated equivalent plastic strains and martensitic volume fractions agree well with the experimental ones, which verify the validity of the constitutive model. Besides, the numerical method is effective at achieving a realistic surface coverage. The maximum compressive residual stress by the Johnson–Cook model is 12% higher than that of the proposed model. Additionally, each hardening effect has an effect on the simulated residual stress. The developed numerical approach can provide a feasible simulation of the shot-peening process and makes an accurate prediction of the residual stress field in 301LN steel.

Experimental Investigation on the Effect of Shot Peening and Deep Rolling on the Fatigue Response of High Strength Fasteners

Shot-peening and deep rolling are mechanical surface treatments that are commonly applied to enhance the fatigue performances of components, owing to their capacity to generate compressive residual stresses and induce work hardening. However, literature is still poor of published data concerning the application of these treatments to high strength steels fasteners, although these represent a class of components among the most widespread. In the present work, the impact of deep rolling and shot-peening performed in the underhead radius of two set of fasteners made of 36NiCrMo and 42CrMoV for fatigue life enhancement has been investigated. The experimental tests consisted of six combinations of shot-peening and deep rolling, including the non-treated state. Two test campaigns have been sequentially carried out with different process parameters and treatment sequences. The results always showed a beneficial impact of the deep rolling on fatigue, especially for the 42CrMoV steel. Conversely, the effect of the shot-peening strongly depended on the selected set of parameters, alternatively leading to an improvement or a worsening of the fatigue life in relation to the level of induced surface roughness.

Improvement of Fatigue Strength of Additive Manufactured Metals by Solid-Liquid-Gas Interfacial Phenomena Induced by Pulse Laser

Although additive manufactured (AM) metals are attractive materials, the fatigue strength of AM metals are considerably weak comparing with that of wrought materials. The mechanical surface treatment such as shot peening can improve the fatigue strength of metallic materials. Recently, a novel mechanical surface treatment using solid-liquid-gas interfacial phenomena induced by pulse laser has been developed. In the present paper, in order to demonstrate the improvement of fatigue strength of AM metals by solid-liquid-gas interfacial phenomena, titanium alloy Ti6Al4V manufactured by electron beam melting EBM was treated by submerged pulse laser and tested by a plane bending fatigue test. The key factors were investigated by evaluating the relation between the fatigue properties and mechanical properties of the surface treated by submerged laser peening, cavitation peening and shot peening.

High Speed Orbital Drilling Optimization and Fatigue Life Enhancement by Orbital Roller Burnishing for Aluminum Alloy

<div class="section abstract"><div class="htmlview paragraph">Orbital drilling has proved to be advantageous to achieve aeronautical-level quality drilling (surface roughness, geometry control…) fully adapted for complex assemblies in a single operation. However, compared to conventional drilling method, this process leads to a drastic change in structure’s fatigue life probably due to a non-optimised level of residual stress. The control of the mechanical behaviour of parts obtained by orbital drilling is the goal of the European-CleanSky collaborative R&D project RODEO (Robotized Orbital Drilling Equipment and Optimized Residual Stresses, GA no.738219). In this work, an orbital drilling unit (ORBIBOT) allowing high speed machining conditions was developed by PRECISE France, that can be integrated on a lightweight industrial robot. Cutting parameters were determined through an original Tool-Material Couple optimization strategy dedicated to orbital drilling, developed with MITIS Engineering and carried out on 2024-T351 Aluminum alloy. In order to enhance the mechanical behaviour of the system (fatigue, surface hardening…), an innovative mechanical surface treatment has been introduced for investigations: orbital roller burnishing, performed right after orbital drilling. The burnisher follows a helical path around the hole axis. Orbital burnishing and its associated tool have been patented by PRECISE (N°FR16 60693). A comparative study between axial drilling, orbital drilling and orbital drilling+burnishing was done in terms of hole diameter, surface roughness, burr height, fatigue life…. Performances and quality levels obtained by using orbital drilling (with or without burnishing) are significantly different compared to conventional drilling. On open-hole samples, a significative fatigue life improvement was exhibited using orbital drilling, even more important with burnishing. Tests were performed also on filled-hole configurations. The innovative coupling of orbital drilling and burnishing tools suggested by PRECISE offers new high-speed machining opportunities, especially in the controlled strain hardening and residual stresses domains.</div></div>

Fabrication of composite modified layer on aluminium alloy by surface mechanical nano-alloying combined with nitriding

A composite modified layer was fabricated on 6061 aluminium alloy by means of surface mechanical nano-alloying treatment (SMNAT) combined with nitriding treatment. The microstructure, mechanical properties and interfacial bond of composite modified layer were investigated systematically. The experimental results showed that a Fe coating with thickness of 40–65 μm could be fabricated on the surface of 6061 aluminium alloy by means of SMNAT for 1 h. The mean grain size of top surface layer in Fe coating is about 15 nm. After nitriding, a composite modified layer was generated and its microstructure is depended on the nitriding temperature. The phase structure of modified layer on samples after nitriding at 450 °C, 550 °C and 640 °C is Fe2-3N/Fe(N), Fe2-3N/Fe(N) and Fe2-3N/Fe2Al5, respectively. The properties measurements showed that the surface hardness of 6061 aluminium alloy was greatly enhanced by SMNAT combined with nitriding treatment. The hardness increased with increase of nitriding temperature. Additionally, the mechanical properties match and interfacial bond strength of layer-substrate on the N450 and N550 samples is better than those on the N640 sample. This paper offers a novel method to prepare a gradient modified layer on aluminium alloy for improving surface properties.

Influence of Shot Peening Treatment in Erosion Wear Behavior of High Chromium White Cast Iron

High alloy white cast irons (WCI) play an important role in many industrial fields such as mining, cement industry, or grinding due to their high hardness and wear resistance. In all these processes, white cast iron components must work under erosion and abrasion conditions. Many investigations have been carried out with the aim of improving the mechanical properties of this type of alloys. Wear resistance depends on the mechanical properties, mainly hardness. Thus, the WCI are typically heat treated in order to modify its microstructure, improving its tribological and wear behavior. The aim of this study is to propose a mechanical surface treatment, shot peening, as an alternative to global heat treatments, due to its capacity to induce phase transformation and microstructural modification, at the same time that it improves the mechanical properties of materials. Characterization of different treated samples was performed by means of microstructural characterization, X-ray diffraction analysis, SEM observation, hardness and roughness measurements, and erosion tests. The results show that shot peening treatment is able to transform residual austenite and increase hardness in the top surface layer of the material. Both effects contribute to improve the erosion wear behavior of the WCI.

Mechanical Surface Treatments of AISI 304 Stainless Steel: Effects on Surface Microrelief, Residual Stress, and Microstructure

The surface roughness, residual stress, and microstructure of AISI 304 stainless steel specimens after laser shock peening (LSP), water jet cavitation peening (WjCP), water jet shot peening (WjSP), and multi-pin ultrasonic impact treatment (UIT) were studied in this work. Compared to the initial state, the surface roughness (Ra) was, respectively, decreased by approx. 5.5, 7.8, 38.2, and 91.1% after the LSP, WjCP, WjSP, and UIT processes. The volume fraction of e-martensite of ~ 3-5% was observed in all treated specimens except for the LSP-treated ones. The volume fraction of α′-martensite was increased in the following sequence: WjCP (~ 5%), LSP (~ 5%), WjSP (~ 25%), UIT (~ 50%). The studied mechanical surface treatments promote a significant reduction in grains size of both austenite (~ 15-20 nm) and martensite (~ 20-37 nm) leading to essential hardening. All studied processes result in the formation of compressive residual stresses (− 377…693 MPa) and the improvement in the bearing curve parameters. The microhardness estimated accounting for the contributions of different hardening mechanisms to the yield strength magnitude correlates well with the experimental data. The grain boundary hardening and dislocation hardening are concluded to be the most influential mechanisms.

High-performance fiber reinforced concrete as a repairing material to normal concrete structures: Experiments, numerical simulations and a machine learning-based prediction model

High-performance fiber reinforced concrete (HPFRC) has been reported as a repairing material to normal concrete (NC) structures due to its predominant mechanical performance. Here, we investigate the debonding behavior between HPFRC and NC subjected to direct shear loading. HPFRC specimens are fabricated and experimentally calibrated to determine the compressive and bending (i.e., flexural) strengths. HPFRC-NC samples are fabricated using two bonding strategies, i.e., mechanical surface treatments with and without chemical agent. Direct shear loading is applied to test the HPFRC-NC debonding behavior. A finite element (FE) model is developed to predict the direct shear debonding response. The FE model is validated by the experimental observations and then used to characterize the debonding behavior with various geometric and material parameters, as well as bonding interface treatments. Subsequently, a robust machine learning model is developed to formulate the shear debonding strength of HPFRC-NC with those influencing parameters. Design examples are presented to illustrate the efficiency of the proposed machine learning model in describing the debonding response of HPFRC-NC. A sensitivity analysis is further conducted to investigate the contribution of the chosen predictors to the debonding behavior of HPFRC-NC. The reported HPFRC and machine learning-based prediction model provide powerful tools to address repairing issues in various existing normal concrete structures.

Surface hardening of 36 NiCrMo 6 steel by ball burnishing process

This work aims to characterize the 36 NiCrMo 6 steel in monotic traction. The tested samples were subjected to mechanical surface treatment (MST) by diamond ball burnishing. This process allow it possible to modify the physical and geometrical properties of the material. The stress-strain diagram obtained were processed and digitalised. The hardening domain was modelled and rational curves were established, taking into account the stresses triaxiality. Thus, the work hardening exponent of material considered was evaluated. The effect of ball burnishing on this exponent has studied in proceeding a comparative manner between burnished and machined surface. The results obtained show that by applying the optimal parameters for burnishing, the work hardening exponent of pre-machined surface layer can be increased by 10%, where nB = 0.407 (nT = 0.312 machined surface).

Effect of Surface Mechanical Treatments on the Microstructure-Property-Performance of Engineering Alloys.

Fatigue is a dominant failure mechanism of several engineering components. One technique for increasing the fatigue life is by inducing surface residual stress to inhibit crack initiation. In this review, a microstructural study under various bulk (such as severe plastic deformation) and surface mechanical treatments is detailed. The effect of individual microstructural feature, residual stress, and strain hardening on mechanical properties and fatigue crack mechanisms are discussed in detail with a focus on nickel-based superalloys. Attention is given to the gradient microstructure and interface boundary behavior for the mechanical performance. It is recommended that hybrid processes, such as shot peening (SP) followed by deep cold rolling (DCR), could enhance fatigue life. The technical and scientific understanding of microstructural features delineated here could be useful for developing materials for fatigue performance.

Experimental investigation into the effects of deep cold rolling on the surface quality and hardness of brass C38500

In the current study, the effect of deep cold rolling (DCR) as a mechanical surface treatment on the surface quality of C38500 brass alloy is investigated. To this end, the surface roughness and hardness of the raw material is measured firstly using the roughness and hardness tester. A simple tool is designed and fabricated for performing the treatments using surface pressure induced by a small ball. DCR process is accomplished by different kinds of balls to determine the effects of ball hardness on the surface roughness and hardness. Then roughness and hardness tests are carried out for the treated specimens. Results show about 93% and 8.4% improvement for surface roughness and hardness regarding to best conditions, respectively. Also, subsurface hardness shows this treatment can shift the hardness curves to higher values. It is also obtained that different materials for ball and its surface quality as well as different rolling depths caused various results. The minimum surface scratches (roughness) of ball leads to high quality treated specimen. Higher ball hardness causes as well more deformation on the surface of specimen similar to higher rolling depth.

Use of an Abrasive Water Cavitating Jet and Peening Process to Improve the Fatigue Strength of Titanium Alloy 6Al-4V Manufactured by the Electron Beam Powder Bed Melting (EBPB) Additive Manufacturing Method

Metal components made by additive manufacturing have large inherent surface roughness, and, as such, their strength and fatigue life can be reduced significantly versus wrought products. In order to improve these properties, a novel mechanical surface treatment that introduces compressive residual stress while simultaneously reducing the surface roughness is proposed. The proposed treatment uses cavitation peening combined with an abrasive slurry. The impact of the kinetic energy-charged abrasive particles, induced by collapsing water cavitation vapor bubbles, produces compressive residual stress, while the abrasive reduces the surface roughness. Plane-bending fatigue tests were carried out to determine the effectiveness of this treatment on the fatigue life and strength of titanium alloy Ti6Al4V manufactured by electron beam melting. It was demonstrated that the fatigue strength of an as-built specimen was improved from 169 MPa to 280 MPa by the proposed treatment.

Impact of the Process Parameters, the Measurement Conditions and the Pre-Machining on the Residual Stress State of Deep Rolled Specimens

Mechanical surface treatments, e.g., deep rolling, are widely spread finishing processes due to their ability to enhance the fatigue strength of the treated materials with means of cold working and inducement of favorable compressive residual stresses. Despite of the clear advantages of deep rolling, the controlled generation of compressive residual stresses is still a challenging task, as the process can be influenced by the pre-machining stress state of the treated material. Additionally, the exact characterization of the induced residual stress field is impacted by the specific characteristics of the applied measurement technique. Therefore, this paper is focused on the X-ray diffraction residual stress analysis of deep rolled specimens, pre-machined to achieve rough or polished surface. The deep rolling process was realized as a single-trace to avoid the influence of the other process parameters and the resulted residual stress field on the surface and in depth was investigated. Additionally, the surface residual stress profiles were determined using two different measuring devices to analyze the impact of the different measurement conditions.