Surface Mechanical Treatment Research Articles

Improvement in fatigue strength of 41Cr4 steel through slide diamond burnishing

Slide burnishing (SB) is a static mechanical surface treatment based on the severe plastic deformation of the surface for which the contact between the deforming element and the surface being treated is sliding friction. SB improves the surface integrity of metal structural and machine components dramatically. This paper is devoted to improving the fatigue strength of 41Cr4 steel hourglass-shaped specimens subjected to SB with a spherical-ended deforming diamond via different combinations of basic governing parameters. Since the residual compressive stresses introduced play a significant role for the fatigue behavior of the burnished components, a comprehensive parametric study of the SB process was conducted using fully coupled thermal-stress finite element (FE) simulations. The FE model’s adequacy was proven via comparison of the FE results for the residual stresses with X-ray diffraction measurements. The results obtained show that the diamond radius and the burnishing force have the strongest effects on the residual stresses, which, in turn, have a significant influence on the fatigue strength, respectively, fatigue life. An extensive experimental investigation of the effect of the selected SB basic parameters on the fatigue limit of the slide burnished specimens was carried out using Locatti’s method. The latter is based on the Palmgren–Miner linear damage hypothesis, which is a particular case of a general cumulative damage theory. A planned experiment was carried out, with the governing factors changed among four levels. Regression analysis of the experimental results was carried out, and a model for predicting the fatigue limit was obtained. Based on the model obtained, a one-purpose optimization was carried out using a genetic algorithm. By means of the optimal basic parameters, the fatigue limit of the processed specimens was increased by 22.7%—from 440 to 540 MPa. The fatigue life increased more than 100 times over after SB with the optimal basic parameters.

Treatment of chronic periodontitis by non-surgical periodontal therapy in association with diode laser compared to conventional non-surgical therapy

Mechanical surface treatment and removal of the above and subgingival biofilm (Tartar ablation; SRP) are consideredthe most suitable tools for the treatment of periodontal inflammatory diseases, with the aim of destroying bacterialbioflim, reducing bacteria, and slowing down recolonization by pathogenic microorganisms.Often, however, the only S&RP are not enough, as there are patients who are experiencing relapses.Recently, laser therapy has been suggested as a potential tool to improve the outcome of periodontal non-surgicaltreatment.The objective of the following study was to evaluate the clinical healing of periodontal pockets treated with mechanical therapy, scaling and root planing, and diode laser application, compared to that obtained with non-surgical mechanical therapy alone.The study was designed as a randomized controlled clinical trial. Patients in the control group (13 patients) underwent conventional non-surgical therapy only, while patients in the test group (17 patients) were associated withconventional non-surgical treatment, a laser irradiation session.At baseline and after 6 months, the parameters of probing depth (PD), bleeding on probing (BOP), gingival recession(REC) were assessedThe main variable of this study was the PD (probing depth)FMPS and FMBS at follow-up improved in both groups. The FMPS baseline test group 32.59 ± 6.74 - follow up 12.00± 3.16.The baseline of the control group showed 33.00 ± 9.55, the follow up 13.15 ± 4.85 The FMBS baseline test groupfound 24.29 ± 5.01 while at follow 9.65 ± 2.69. The baseline control group 30.31 ± 7.74, Follow up 11.08 ± 2.33.There is a statistical significance. (P.VALUE 0.0001)There were no significant differences between the groups in terms of PD, CAL and BOP at baseline and at follow-up.PD Test group 4,89±1,58 3,95±0,85 0,0001Control group 5,02±1,57 4,01±0,86CAL (mm)Test group 0,89±2,29 0,77±1,91Control group 0,28±1,38 0,24±1,14REC Test group 0,19±0,49 0,19±0,51Control group 0,06±0,29 0,57±029BOP Test group 51,2% 23,5%Control group 54,0% 20,9%The results showed differences in both baseline and follow-up for REC.Test group 0,19±0,49 0,19±0,51Control group 0,06±0,29 0,57±029In intra-group analyzes, there are differences between baseline and follow-up for all values, except for REC in thecontrol group.The diode laser can be used as an appropriate device for periodontal treatments, but it can offer additional andsignificant benefits if used according to appropriate protocols and parameters, and especially if associated withnon-surgical, manual and ultrasound periodontal instrumentation, always site-specific , as it is a tool that does notreplace traditional methods.

The treatment of chronic periodontitis by non-surgical periodontal therapy in association with diode laser compared to conventional non-surgical therapy

Mechanical surface treatment and removal of the above and subgingival biofilm (Tartar ablation; SRP) are considered the most suitable tools for the treatment of periodontal inflammatory diseases, with the aim of destroying bacterial bioflim, reducing bacteria, and slowing down recolonization by pathogenic microorganisms. Often, however, the only S&RP are not enough, as there are patients who are experiencing relapses. Recently, laser therapy has been suggested as a potential tool to improve the outcome of periodontal non-surgical treatment. The objective of the following study was to evaluate the clinical healing of periodontal pockets treated with mechanical therapy, scaling and root planing, and diode laser application, compared to that obtained with non-surgical mechanical therapy alone. The study was designed as a randomized controlled clinical trial. Patients in the control group (13 patients) underwent conventional non-surgical therapy only, while patients in the test group (17 patients) were associated with conventional non-surgical treatment, a laser irradiation session. At baseline and after 6 months, the parameters of probing depth (PD), bleeding on probing (BOP), gingival recession (REC) were assessed The main variable of this study was the PD (probing depth) FMPS and FMBS at follow-up improved in both groups. The FMPS baseline test group 32.59 ± 6.74 - follow up 12.00 ± 3.16. The baseline of the control group showed 33.00 ± 9.55, the follow up 13.15 ± 4.85 The FMBS baseline test group found 24.29 ± 5.01 while at follow 9.65 ± 2.69. The baseline control group 30.31 ± 7.74, Follow up 11.08 ± 2.33. There is a statistical significance. (P.VALUE 0.0001) There were no significant differences between the groups in terms of PD, CAL and BOP at baseline and at follow-up. PD Test group 4,89±1,58 3,95±0,85 0,0001 Control group 5,02±1,57 4,01±0,86 CAL (mm)Test group 0,89±2,29 0,77±1,91 Control group 0,28±1,38 0,24±1,14 REC Test group 0,19±0,49 0,19±0,51 Control group 0,06±0,29 0,57±029 BOP Test group 51,2% 23,5% Control group 54,0% 20,9% The results showed differences in both baseline and follow-up for REC. Test group 0,19±0,49 0,19±0,51-Control group0,06±0,29 0,57±029 In intra-group analyzes, there are differences between baseline and follow-up for all values, except for REC in the control group. The diode laser can be used as an appropriate device for periodontal treatments, but it can offer additional and significant benefits if used according to appropriate protocols and parameters, and especially if associated with non-surgical, manual and ultrasound periodontal instrumentation, always site-specific , as it is a tool that does not replace traditional methods.

Low velocity impact of hybrid stacked steel plates

Designing and manufacturing high strength, low weight parts with enhanced impact resistance is highly sought after in the transportation industry. The most common methods to improve strength-to-weight ratios of impact targets is a composite material composition or a favorable geometric design. An alternative method to improve impact performance is functionally gradient mechanical properties in a single material by hybrid additive stacking. In this study, low velocity impact tests were conducted on hybrid stacked 1070 steel plates where individual layers were subjected to shot peening (SP) to functionally grade mechanical properties. Hybrid additive stacking refers to secondarily processing preferential layers within a stacked build volume by cold working to achieve favorable compressive residual stresses and localized work hardening. Incorporating SP on preferential layer intervals during stacking is a radically different approach to increase the strength-to-weight ratio and impact performance of metals. Cold working individual layers by peening achieves functionally gradient mechanical properties in a single material without the need for multi-material composite manufacturing. The objective of this work was to investigate the impact strength and energy absorption from stacking shot peened and non-shot peened layers to form a hybrid target. Identifying favorable stacking sequences provides insight on how to design a hybrid structure that incorporates a mechanical surface treatment (e.g., shot peening) to outperform conventional and composite targets. Results showed energy absorption improved by incorporating stacked shot peened layers and was dependent on the sequence. The improvement in impact performance was attributed to the shot peening induced compressive residual stresses and increased friction incorporated within predefined layers.

Effect of Various Surface Treatments on Ti-Base Coping Retention.

Mechanical surface roughening of the titanium-abutment base is necessary to increase the pull-off bond strength of the lithium disilicate abutment material. Additional chemical surface treatment may further increase the bond strength, but the effects are product specific.

Surface Integrity and Oxidation of a Powder Metallurgy Ni-Based Superalloy Treated by Laser Shock Peening

Laser shock peening (LSP) is a mechanical surface treatment which can induce large compressive residual stresses and microstructural changes in a material by using repetitive shocks from laser pulses. In this work, the surface integrity (surface microstructure, topography, hardness and residual stress) of a LSP-treated powder metallurgy Ni-based superalloy was investigated for the first time. LSP treatment introduced large plastic deformation especially at a depth of about 100 μm from the surface, which increased the local hardness. The residual stress from the surface to the interior of the sample was investigated by synchrotron x-ray diffraction. The maximum compressive stress reached 400 MPa at the surface, while the depth of the compressive stress is about 0.7 mm. Lastly, the oxidation behavior of the treated and untreated samples was evaluated by thermal exposure at 700°C for 312 h. The LSP treatment decreased the thickness of the oxide layer, thereby showing improved oxidation resistance.

Influence of Nanocrystalline–Amorphous Composite Layer on Tensile Properties of Pure Titanium

Ultrasonic shot peening (USP) is a mechanical surface treatment that induces rapid surface nanocrystallization and partial amorphization. The USP treatment can improve the surface properties but may also influence the integral mechanical performance, e.g., tensile properties. In this study, the tensile properties of USP-treated pure titanium plates were determined. The investigation of microstructures (before and after tensile tests) and the fracture morphology was performed by XRD, SEM and HRTEM methods. According to the experimental results, the influence of the nanocrystalline–amorphous (NC–A) composite layer on ultimate tensile strength (UTS), yield strength, fracture elongation and the fracture mode was studied and discussed. Besides, the relationship between surface hardness and UTS of the USP-treated titanium plates was analyzed and a predictive model for determination of the UTS of the USP-treated pure titanium plate using surface hardness and thickness of NC-A layer or USP parameters was established. The experimental and calculated results are in good agreement with the correlation coefficient of 0.9714.

Effects of High-Temperature Deep Rolling on Fatigue, Work Hardening, and Residual Stress Relaxation of Martensitic Stainless Steel AISI 420

The deep-rolling, mechanical surface treatment was modified by applying heat during operation on the martensitic stainless steel AISI 420. Fatigue performance of the high-temperature deep-rolled condition was investigated and compared with the non-surface-treated and room-temperature deep-rolled conditions. Thermal and mechanical relaxation behaviors of residual stresses and work-hardening states were investigated. Annealing processes were carried out at a temperature range of 300-600 °C, with soaking times between 0.1 and 104 min for thermal relaxation. Fatigue tests were carried out at given stress amplitudes of 517-600 MPa, with the different number of cycles for the mechanical relaxation. The residual stresses and work-hardening states were determined using x-ray diffraction with the sin2Ψ method. It was found that the thermal relaxation can be described with the Zener–Wert–Avrami function. The relaxation mechanism was changed from the volume diffusion of the room-temperature deep-rolled condition to the dislocation-cored diffusion of the high-temperature deep-rolled condition. The mechanical relaxation of compressive residual stresses was higher than that of the work-hardening states. The residual stresses of the high-temperature deep-rolled condition are more stable than those of the room-temperature deep-rolled condition under cyclic loading.

An evaluation of the effect of the chemical and mechanical surface treatment of the glass fibre posts on the retention of the composite resin core material: An in-vitro study

An evaluation of the effect of the chemical and mechanical surface treatment of the glass fibre posts on the retention of the composite resin core material: An in-vitro study - APRD- Print ISSN No: - 2581-4796 Online ISSN No:- 2581-480X Article DOI No:- 10.18231/j.aprd.2019.025, IP Annals of Prosthodontics and Restorat

Heat transfer and convection of evaporating sessile droplets in transition from superhydrophilic to superhydrophobic structured wall: Optimization of functional properties

Abstract The free convection and heat transfer of evaporating water droplets on a textured wall have been studied. The analysis of the influence of micro- and macrotextures on the heat transfer coefficient has been performed. Structured surfaces were created by two different methods: mechanical surface treatment and laser exposure. The behavior of heat transfer on a structured wall was compared with that on a smooth surface. The wettability of the wall varied over a wide range of contact angles (the transition from a superhydrophilic to a superhydrophobic surface was considered). Simple relations have been obtained to estimate the separate influence of several key factors (the drop height, the surface area of the wetted spot of the drop, the convection velocity in the liquid and the temperature difference in the drop). The obtained data are important for designing heat exchangers with structured walls and for optimizing the functional properties.

Improving the high temperature oxidation resistance of Ti-β21S by mechanical surface treatment

The improvement of the high temperature oxidation resistance of titanium alloys is currently a technological challenge. Mechanical surface treatments as shot-peening (SP) have shown their ability to improve the behaviour of pure zirconium and titanium. However, shot-peening treatments can induce a significant surface contamination. Laser shock peening (LSP) appears as a good alternative. Here, we have investigated the effect of SP and LSP treatments on the HT oxidation behavior of Ti-β21S. Samples treated by these methods have been compared to untreated ones for long exposures (3000 h) at 700 °C in dry air. The samples placed in a furnace at 700 °C were periodically extracted to be weighed. The results have been compared to that of pure commercial titanium (Ti-α) samples studied in the same conditions. The higher performances of the Ti-β21S alloy, and the beneficial effect of the SP treatment, and even more of the LSP one, on the HT oxidation resistance of Ti-β21S have been clearly shown. The effect of the mechanical treatments on the microstructure of the Ti-β21S samples and the changes induced by the long duration exposure at high temperature have been mainly studied by scanning electron microscopy combined with energy and wavelength dispersive spectrometry.

Complementary Machining: Effect of tool types on tool wear and surface integrity of AISI 4140

Abstract Complementary Machining is a process strategy for the time-efficient mechanical surface treatment of metallic workpieces. The characteristic of Complementary Machining is that after machining, a mechanical surface treatment is carried out using the cutting tool. The cutting tool moves over the workpiece surface in opposite direction to the machining process and induces an elastic-plastic deformation in the surface layer. Previous investigations have shown the possibility to achieve life-enhancing surface layer states in turning of AISI 4140 with Complementary Machining and to achieve fatigue strengths comparable to those after shot peening. In this paper, the influence of the tool types and process parameters, such as the feed rate, on the resulting topography and the tool wear, represented by changes of cutting edge microgeometry, during Complementary Machining of AISI 4140 are investigated based on the previous investigations. In addition to different substrates of the cutting insert, the focus of the investigations is also on the influence of tool coating. Both the tool wear and the resulting topography were analyzed tactilely and correlated with the process parameters. The results show a clear influence of the used substrate of the cutting insert and coating on the tool wear and the resulting topography.

Repair strength and surface topography of lithium disilicate and hybrid resin ceramics with LLLT and photodynamic therapy in comparison to hydrofluoric acid.

The aim was to compare the repair bond strength and surface topography of lithium disilicate ceramics (LDC) and hybrid resin ceramics (HRC) using different surface conditioning treatments [low level laser therapy (LLLT), photodynamic therapy (PDT), hydrofluoric acid (HF) with silane and air abrasion (AA) and silane]. Sixty specimens each of LDC and HRC were used. Discs were prepared for each group (6 × 2 mm), conditioned using different regimes. Specimens in group 1 and 5 were laser irradiated using Er,Cr:YSGG (ECYL), group 2 and 6 were conditioned using methylene blue photosensitizer (PDT), group 3 and 7 surface was treated with hydrofluoric acid and silane (HFA-S), group 4 and 8 conditioned with Al2O3 air abrasion and silane (AA-S). A Porcelain Repair Kit was used according to manufacturer recommendation in all samples. Peak universal bond adhesive was rubbed on ceramic surface and then bonded with composite resin. For shear bond strength testing the specimens were placed in a universal testing machine. A stereomicroscope at 40x magnification was used to analyse failure pattern. Five specimens in each group after surface treatment were evaluated for surface changes and topography using scanning electron microscopy. The mean repair bond strength was calculated using ANOVA and Tukey's post hoc test at a significance level of (p < 0.05). The highest repair bond strength was observed in group 3 (LDC) (20.57 ± 3.58 MPa) (HFA-S), whereas, the lowest score was displayed in Group 2 (LDC) using methylene blue photosensitizer (MBPS) (12.18 ± 1.08 MPa). Similarly, in HRC the highest repair SBS was presented in group 8 (AA-S) (20.52 ± 2.51 MPa) and the lowest SBS values were exhibited by PDT treated group 6 (13.22 ± 0.62 MPa). A combination of mechanical and chemical surface treatments should be used in order to achieve adequate repair bond strength between resin composites and ceramic interface of LDC and HRC.

Effect of mechanical surface treatments on the high temperature oxidation of pure titanium: the role of nitrogen

The mechanically treated high temperature (700°C) oxidation of commercially pure titanium was studied for long exposures (3000 h). The treatments studied here are the shot-peening and the laser-shock peening. The mass gain was measured by discontinued weighing. SEM and Raman imaging revealed strong differences between laser-shock peened, shot-peened and untreated oxidized samples. The laser treatment leads to thin compact and protective oxide layer while the shot-peened and untreated samples exhibit cracked oxide layers. The distribution of light elements like carbon, oxygen and nitrogen was revealed by Ion Beam Analysis. The presence of nitrogen located at the interface between the oxide scale and the metal was revealed on laser-shock peened samples. It is supposed the nitrogen slows-down the oxygen diffusion into the metal. The extent of the oxygen-enriched metal is also smaller on LSP samples, which improves the ductility of titanium.

Improve Surfaces properties of ABS Products fabricated by fused deposition modeling (FDM) 3D Printing

FDM (fused deposition modeling) 3D printing products often suffer from high surface roughness and low durability compared to conventional methods. In this paper, the effect of surface treatment after printing and coating with a layer of metal on its properties has been studied, The mechanical surface treatment methods (sandpaper) and chemical (solvent treatment) were compared and their effect on the adhesion strength of the deposited metal layer on the surface. The surface of the ABS product was coated with a layer of metal, the effect of both treatment and coating on the mechanical properties of printing products was studied. The results showed a clear decrease in surface roughness after surface treatment, where surface roughness decreased by 92%, and the best result was when grinding with sandpaper (2000 Grit) was Ra 0.35 μm. The tensile strength after acetone surface treatment was improved by 50% and after coating the product with a layer of metal by 56.25%. The adhesion test of the surface-deposited metal (CROSS-CUT) was conducted, and the result showed that the best adhesion durability was when the surface was treated with acetone vapor before coating.

Smoothing, deep, or mixed diamond burnishing of low-alloy steel components – optimization procedures

Diamond burnishing (DB) is a static mechanical surface treatment based on severe surface plastic deformation aimed at significant improvement in the surface integrity and operating properties of the treated component. Very often, DB is unjustifiably perceived of as typical smoothing burnishing. In the present article, it is shown that DB can be conducted as smoothing, deep, or mixed burnishing depending on the particular combination of process governing factors employed. Optimizations of the DB process for 41Cr4 steel under different criteria are conducted in order to obtain the optimal parameters of different DB processes. The choices of governing factors and objective functions (roughness and fatigue limits), which are obtained on the basis of planned experiments and regression analyses, are fully justified. By means of one-objective optimizations, the uncompromising optimum values of the objective functions and the corresponding optimum values of the governing factors of smoothing and deep DB processes are obtained. A new optimization procedure for solving a multi-objective optimization task is developed in order to obtain compromise optimal values simultaneously with the objective functions and governing factors of the mixed DB process. In order to highlight the advantages of the proposed optimization procedure, the multi-objective task solution is compared with the results obtained via some known methods, i.e., the compromise weight vector and function of the losses methods.

Dynamics of Nonlinear Processes of Corrosion of Non-Nikel Titanium Shape Memory Alloy

Research of dynamics of nonlinear corrosion processes of non-nickel titanium shape memory alloy Ti-20Nb-10Ta is performed. Samples were placed in mediums imitating physiological liquids, with ðÍ from 1.68 to 9.18. 3 types of samples were used: in an initial state, after thermal (annealing) and surface mechanical treatment. After annealing, there is a slight narrowing of the X-ray peaks, which indicates stress relief. New phases are not allocated. The alloy is a substitution solution with a b-Ti lattice. The greatest release of titanium ions was observed in solution with the sourest environment and samples after annealing. Release of niobium and tantalum ions in solution with any acidity was not observed.

Graphite surface profile with different polishing treatment

Graphite is a fascinating material to study in nanotechnology. Surface profile and roughness of the graphite are some of the most important parameters to determine many physical and mechanical behaviors including friction or bonding condition. To acquire certain surface profile, mechanical polishing treatment is one of the easiest ways that can be applied. In this work, graphite is polished by three different grades of sandpapers (P800, P400, and P220) and cellulose-based paper. The surface properties are observed by a laser microscope and various surface roughness parameters were quantified. The sequential polishing process employed in this work is able to modify the surface roughness and might improve the physical properties. This work sheds light on the importance of the mechanical surface treatment on graphite.

Post-processing of the Inconel 718 alloy parts fabricated by selective laser melting: Effects of mechanical surface treatments on surface topography, porosity, hardness and residual stress

The turbine blade test parts were manufactured by the selective laser melting (SLM) process using a nickel-based pre-alloyed Inconel (IN) 718 powder. Various mechanical post-processing techniques, such as barrel finishing (BF), shot peening (SP), ultrasonic shot peening (USP), and ultrasonic impact treatment (UIT), were applied to improve the surface layer properties of the SLM-built specimens. Effects of mechanical surface treatments on surface topography, porosity, hardness, and residual stress were studied. In comparison with the SLM-built state the surface roughness (Sa = 5.27 μm) of the post-processed specimens were respectively decreased by 20.6%, 26.2%, and 57.4% after the BF, USP, and UIT processes except for the SP-treated ones. The Sz parameter was reduced in all treated SLM-built specimens except for the SP-treated ones. The surface microhardness of the SLM-built specimen (~390 HV0.025) was increased after the BF (by 14.2%), USP (by 23.8%), UIT (by 50%), and SP (by 66.5%) processes. The deepest hardened layers were formed after the UIT and SP processes. Residual porosity of the SLM-built specimen was decreased by 23.1%, 40.6%, 55%, and 84% after the BF, SP, USP and UIT processes, respectively. The UIT process formed a densified subsurface layer of significantly reduced porosity (0.118%). All mechanical surface treatments successfully transformed the tensile residual stresses generated in SLM-built specimen into the compressive residual stresses (−201.4...510.7 MPa). The thickness of hardened, densified and compressed near-surface layers ranges from ~80 μm after BF to ~140 μm after USP, and ~180 μm after SP and UIT processes, which correlates to the accumulated energy and deformation extent of the treated surface. The effect of the accumulated energy on the outcomes of the applied surface treatments is also addressed.

Improvement in surface properties of Si wafer by mechanical surface treatment

In the present study, a monocrystalline silicon (Si) wafer was treated by ultrasonic nanocrystal surface modification (UNSM) to enhance the efficiency and service life of Si-based devices by reducing reflectivity and improving surface properties, respectively. Microstructure, surface reflection, surface free energy and dry tribological characteristics of Si wafer before and after UNSM were systematically investigated. A silicon nitride (Si3N4) ball with a diameter of 5 mm was used as a counterface. The wear resistance was enhanced by 23% after UNSM in comparison with that of the as-received Si wafer. The reduction in reflectivity is due to roughened surface, while the improvement in tribological characteristics due to the strengthening. Thus, it is recommended that a UNSM can be potentially used as an alternative mechanical surface treatment for thin Si wafers.