Microhardness Tests Research Articles

Investigating microstructure, mechanical properties, and pitting corrosion resistance of UNS S32760 super duplex stainless steel after linear friction welding

High-performance alloys such as super duplex stainless steels (SDSS) are of interest to the oil and gas industry, especially in deep and ultra-deep reservoirs where high pressures and highly corrosive environments are prevalent. SDSS have high nitrogen contents and pitting resistant equivalent number (PREN) values greater than 40, however, fusion welds of these alloys can exhibit unsuitable microstructures and defects that may result in failure during usage. Solid-state linear friction welding (LFW) offers an alternative for the effective joining of SDSS with a less detrimental effect on microstructure and properties. In this work, four LFW joints in UNS S32760 SDSS were produced and investigated by evaluating the process parameters required to achieve a high-quality joint with the desirable metallurgical, mechanical, and localized corrosion properties. These properties were assessed through metallography (optical microscopy and scanning electron microscopy), tensile and microhardness tests, and corrosion analysis according to the ASTM G48A standard. Results indicated that one specific combination of LFW parameters led to a defect-free joint, and that the mechanical properties of the weld in this case were comparable to those of the base material. Additionally, an adequate balance between ferrite and austenite phases was achieved throughout the microstructural gradients seen in the weld region. Microhardness values were below 350 HV, thus complying with the DNV–OS–F101 standard. Furthermore, no pitting corrosion was observed in this joint under the testing conditions suggested by ASTM G48A.

Assessment of structural defects and mechanical characteristics of IN718/St6 functionally graded material produced by direct laser deposition

Functionally graded materials (FGM) do not show special processing in the composite structure due to the combination of mechanical, thermal, magnetic and stress gradient properties. The aim of this study is to produce IN718/St6 FGM samples by direct laser deposition method. The product of this model should enable the development of mechanical products. Best of all, this can be done without significant reduction in texture and case to residual stress that are a consequence of rapid changes in mechanical and thermal properties in non-FGM samples. To fabricate part, direct laser deposition system equipped with a 1 kW continuous fiber laser is used, SEM/EDS analysis and microhardness testing to measure porosity, chemical composition, and quantify gradient mechanical properties is used. In this study, the cladding composition is selected from 100% IN718 to 100% St6 with a 25% change in St6 composition. To prevent the formation of defects, both single-parameter modes and individual layering are examined, considering the diverse nature of the combination. The result shows that using an individual layering structure, reduces 100% Lack of fusion defects in the IN718/St6 structure. EDS analysis confirmed that the St6 content gradually increased from the first to the fifth layer. The substrate hardness gradually increases from 200 Vickers hardness to 550 Vickers hardness, showing an almost linear trend. Moreover, by using individual layering, the coaxial structure is reduced by 55% and the relative orientation of the vertical line is reduced by 18° compared to using the St6 directly (non-FGM).

Investigation on Microstructural and Mechanical Properties of FeNiMnCrCoTi0.1 High Entropy Alloy with B Addition

High-entropy alloys (HEAs) are alloys with high potential for use in defense, aircraft, and aerospace industries due to their properties such as high strength, hardness, wear resistance, corrosion resistance, and ability to operate at high temperatures. Therefore, in this study, FeNiMnCrCoTi0.1BX (x values in molar ratio, x = 0-1) high entropy alloys were produced by arc melting technique under protective gas atmosphere using a reverse vacuum method. The microstructural properties of the produced HEAs were examined by scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analysis was also performed. The crystal lattice structure of the produced HEAs was determined by X-ray diffraction (XRD) analysis. Microhardness and compression tests were conducted to determine the mechanical properties of the produced HEAs. It is observed that the hardness of the FeNiMnCrCoTi0.1BX high-entropy alloy increases as the boron content increases. The highest microhardness obtained was 593.8 HV in the FeNiMnCrCoTi0.1B alloy. As the boron content increases, the yield stress has also increased in compression testing. The highest yield stress was determined to be 1329 MPa in the FeNiMnCrCoTi0.1B alloy.

Microstructure and Erosion Wear of In Situ TiC-Reinforced Co-Cr-W-C (Stellite 6) Laser-Cladded Coatings.

The article presents research results on the possibility of shaping the structure and properties of Co-Cr-W-C-Ti alloys (type Stellite 6) using laser cladding technology. Cobalt-based alloys are used in several industries because they are characterized by high erosion, abrasion, and corrosion resistance, retaining these properties at high temperatures. To further increase erosion resistance, it seems appropriate to reinforce material by in situ synthesis of hard phases. Among the transition metal carbides (TMCs), titanium carbide is one of the hardest and can have a positive effect on the extension of the lifetime of components made from cobalt-based alloys. In this article, concentration of C, W, and Ti due to the possibility of in situ synthesis of titanium carbides was subjected to detailed analysis. The provided research includes macrostructure and microstructure analysis, X-ray diffraction (XRD), microhardness, and penetrant tests. It was found that the optimal concentrations of Ti and C in the Co-Cr-W-C alloy allow the formation of titanium carbides, which significantly improves erosion resistance for low impact angles. Depending on the concentrations of titanium, carbon, and tungsten in the molten metal pool, it is possible to shape the alloy structure by influencing to morphology and size of the reinforcing phase in the form of the complex carbide (Ti,W)C.

Oxidation resistance, corrosion behavior and grinding performance of laser-deposited TaMoCrTiAl refractory high-entropy coating

In this study, TaMoCrTiAl refractory high-entropy alloy coating without defects was successfully prepared on the Ti6Al4V substrate by laser metal deposited. Microstructure and properties were investigated systematically by multiple characterization methods. The results of phase and morphology experiments indicate that the coating comprised a BCC phase and a partial Laves phase. The coating, with an average thickness of 990 μm, exhibits good metallurgical bonding with the substrate. Further observation reveals that the cladding region consists of irregular bulk crystals. The heat-affected zone has a fine grain size, whereas the substrate has coarse and uneven grains. The high-temperature oxidation test shows that the formation of an Al2O3 oxide layer enhances the coating's high-temperature oxidation resistance. According to the results of microhardness tests, the average microhardness in the coating is about 570.98 HV (1.87 times that of the substrate) due to the formation of the leave phase particles and the fine-grain strengthening. The presence of Titanium, chromium and molybdenum elements in the coating facilitates the formation of a passivation film, thereby enhancing its corrosion resistance. Furthermore, the coating exhibits the smallest grinding force (43.637 N) and the lowest roughness (0.506 μm) at an experimental temperature of 100 °C, which demonstrates that appropriately elevating the experimental temperature can decrease the grinding force and enhance the flatness of the grinding surface.

Effect of Herbal Intracanal Medicaments on Microhardness of Root Dentin: An In Vitro Study.

The use of intracanal medicaments (ICM) is crucial toreduce the microbial load in root canals. However, its application may negatively affect the physical properties of root dentine. Thus, this in vitro study was performed to investigate the effects of different herbalICM on the microhardness ofroot dentin. A total of 100 mid-root discs were randomly divided into five groups (n = 20) and treated with Aloe vera, Aloe vera + chitosan, curcumin, curcumin + chitosan, and control for 14 days. A Vickers hardness indentation machine (Laizhou Laihua Testing Instrument Factory, Yantai, China) with a load of 200 g and a dwell time of 15 seconds was used for microhardness testing before andafter treatment. The results were analyzed usingStatistical Product and Service Solutions (SPSS, version 26.0; IBM SPSS Statistics for Windows, Armonk, NY). Intragroup comparisons were executed using paired t-tests, while intergroup comparisons employed ANOVA, followed by post-hoc Tukey's tests. The Aloe vera + chitosan and curcumin + chitosan groups showed a statistically significant reduction in dentin microhardness (p < 0.05). The decrease in dentin microhardness ofthe Aloe vera and curcumin groups was non-significant (p > 0.05) and similar to that of the control. Aloe vera or curcumin alone as ICM did not affect the root dentin microhardness. The addition of0.2% chitosan to either Aloe vera or curcumin negatively affected the root dentin microhardness.

Investigating the Mechanical and Tribological Properties of Bio-Waste Derived Bioactive Borosilicate Glass Incorporating Strontium Oxide

Abstract The primary goal of the current research paper is to investigate the mechanical and tribological behavior of biologically active glass consisting of 31B2O3-(20-x) SiO2-24.5Na2O-24.5CaO and xSrO (in mol%). The specimens were fabricated partly using bio-waste material, in which Silica and Calcium Oxide were derived from rice husks and egg shells, respectively. The produced specimens underwent immersion in simulated bodily fluid for a week to observe their bioactive response. The bioactive behavior of the samples were examined using X-ray diffraction and FTIR spectroscopy. The compression test and hardness of the specimens were measured using universal testing machine and Vickers micro-hardness tester. Abrasion test of the specimens were performed on pin-on-disc tribometer and the worn-out surfaces were later analyzed using FESEM. The findings from FTIR and XRD analyses validated the existence of a hydroxyapatite layer on the specimen surfaces. Further, XRD data showed an increase in peak intensity after SrO was incorporated, suggesting that it played a supporting role in boosting bioactivity. The mechanical investigations indicated that the addition of SrO adversely affects both hardness and compression strength. The abrasion wear test demonstrated that BSG-5 had the highest wear rate, while BSG-0 exhibited the lowest wear rate among all specimens at a 30 mm track radius. Despite the trade-off between enhanced bioactivity and diminished mechanical strength and wear resistance, incorporating Strontium Oxide makes the glass suitable for applications prioritizing bioactivity, such as bone filling and dental contexts.

Phase transformation and mechanical properties of nanocrystalline Ti–2Fe-0.1B alloy processed by high pressure torsion

In this paper, nano-Ti-2Fe-0.1B alloys with different grain sizes were processed by high pressure torsion (HPT) deformation. The study examined the microstructural evolution of the Ti–2Fe-0.1B alloy during HPT and evaluated its mechanical properties through microhardness and tensile tests. The results of the microstructural observations revealed that the grain size of the Ti–2Fe-0.1B alloy progressively decreased from 3.14 μm in the as-annealed state to approximately 20 nm after 10 turns. In the initial state, the alloy consists of α-phase and β-phases, with a volume ratio of approximately 5:1. During the HPT process, transformations of α-phase and β-phase to ω-phase were observed. The primary reason for this is that the shear forces applied during the HPT process facilitated the phase transformation of the α-phase. Additionally, the presence of Fe element in the alloy altered the lattice compatibility between the grains of β-phase and ω-phase, thereby promoting the phase transformation of the β-phase, with the accumulated turns of HPT process, the fraction of ω-phase increased in the beginning gradually, then decreased, which reached to the maximum 80.8% in the 5 turns. This is higher than that of pure titanium and Ti–Fe alloys under the same conditions, because the proportion of the ω-phase increases with the increase in Fe content. Studies of mechanical properties demonstrated that HPT can substantially enhance the hardness of Ti–2Fe-0.1B alloys to as high as 483 HV, and the tensile strength of the Ti–2Fe-0.1B alloy was observed to increase from 725 MPa to 1568 MPa after 5 turns, which is much higher than Ti–6Al–4V subjected to the identical processing conditions. It can be ascribed to the exist of mass ω-phase as well as finer grain size in nanocrystalline Ti–2Fe-0.1B alloy.

The effect of various treatment parameters in duplex plasma nitrided and diamond-like carbon coating on high-cycle fatigue and fretting fatigue lifetimes of piston pin 16MnCr5 steel

This paper investigates the impact of duplex plasma nitriding and diamond-like carbon (DLC) coatings on the pure fatigue and fretting fatigue properties of 16MnCr5 steel extracted from industrial piston pins used in combustion engines. Two different nitriding and DLC coating processes were performed: "DLC-A" and "DLC-B". The Raman spectrometry and microhardness tests were utilized to evaluate the formation of DLC coating on the sample. Subsequently, the pure and fretting fatigue tests (at 350 MPa and under 100 Hz of the frequency) were performed on as-cast and DLC-coated specimens to obtain the effect of coatings on the fatigue behaviors of the 16MnCr5 steel. Finally, the formation of the DLC layer and the fracture mechanisms were also briefly investigated using field-emission scanning electron microscopy. Then, the obtained results demonstrated that DLC coating ("DLC-B") increased the fatigue lifetime of 16MnCr5 steel by 47.7 % and 85.3 % in pure and fretting fatigue conditions, respectively. This layer can improve the surface properties of engineering materials and components, which can enhance the fatigue lifetime by increasing microhardness and compressive residual stress, reducing wear and friction, and improving adhesion between the substrate and coating. However, due to the white layer, the “DLC-A” improperly enhanced the material performance.

Study on the Tribological Properties of DIN 16MnCr5 Steel after Duplex Gas-Nitriding and Pack Boriding.

DIN 16MnCr5 is commonly used in mechanical engineering contact applications such as gears, joint parts, shafts, gear wheels, camshafts, bolts, pins, and cardan joints, among others. This study examined the microstructural and mechanical properties and tribological behavior of different surface treatments applied to DIN 16MnCr5 steel. The samples were hardened at 870 °C for 15 min and then quenched in water. The surface conditions evaluated were as follows: quenched and tempered DIN 16MnCr5 steel samples without surface treatments (control group), quenched and tempered DIN 16MnCr5 steel samples with gas-nitriding at 560 °C for 6 h, quenched and tempered DIN 16MnCr5 steel samples with pack boriding at 950 °C for 4 h, and quenched and tempered DIN 16MnCr5 steel samples with duplex gas-nitriding and pack boriding. Microstructure characterization was carried out using metallographic techniques, optical microscopy, scanning electron microscopy with energy-dispersive spectroscopy, and X-ray diffraction. The mechanical properties were assessed through microhardness and elastic modulus tests using nanoindentation. The tribological behavior was evaluated using pin-on-disc tests following the ASTM G99-17 standard procedure under dry sliding conditions. The results indicated that the surface treated with duplex gas-nitriding and pack boriding exhibited the highest wear resistance and a reduced coefficient of friction due to improved mechanical properties, leading to increased hardness and elastic modulus.

The effects of adding Si3N4 as a nitrogen source on the properties of Ni-Free Co-28Cr-6Mo-xN alloy powders developed by mechanical alloying

Co-Cr-Mo alloys, which also contain Ni, are often used as materials for implants in orthopedic surgery due to their excellent mechanical properties and resistance to corrosion. However, when these alloys are implanted into the body, they can release nickel ions into the host tissues, which can pose health risks over time. To address this issue, nitrogen can be substituted for nickel. This study involves the synthesis of cobalt-based alloy powders, following the chemical composition specified by ASTM F1537, using different percentages of silicon nitride as a nitrogen source via the mechanical alloying method in an argon atmosphere. The effects of increasing silicon nitride content on the particle morphology, particle size, phase transformations, microstructure, and hardness of the synthesized powders were investigated using XRD, SEM, TEM, and microhardness tests. The results obtained from the X-ray diffraction analysis indicate that the alloying process was conducted effectively. It was observed that the silicon nitride underwent decomposition, and a portion of its nitrogen reacted with chromium to form the chromium nitride phase. Additionally, it was observed that an increase in the silicon nitride content resulted in a decrease in crystallite size and an increase in lattice strain. Adding silicon nitride in varying percentages resulted in crystal sizes within the nanometer range. The SEM results indicated that the size of powder particles decreased with an increase in the content of silicon nitride, and there was a more uniform distribution of particle sizes, with less variation in size. The TEM images showed that all percentages of silicon nitride resulted in a fine-grained polycrystalline phase, where the size of the crystallites decreased with an increase in the amount of silicon nitride. The corresponding SAED patterns supported this observation. Moreover, the hardness of the material increased as the silicon nitride content increased.

Performance of low shrinkage Bis-EFMA based bulk-fill dental resin composites

ObjectivesThe purpose of this study was evaluating the performance of new Bis-EFMA based bulk-fill composites with common methacrylate based composites and commercial dental composites. MethodsThe Bis-EFMA monomer was synthesized and the novel Bis-EFMA based bulk-fill composites were prepared. The resin composite samples were co-cultured with human gingival epithelial cells and human dental pulp stem cells to test the biocompatibility. The edge adaptation was observed under a combination of stereoscope and scanning electron microscope. The internal hardness was measured using a Vickers microhardness tester after one-time filling of cavities prepared in extracted teeth. After friction and wear test on the surface of the resin composites, the surface morphology and volume wear of each group were measured by the optical profilometer. The color stability was measured by a colorimeter. ResultsDirect contact with human gingival epithelial cells and human dental pulp stem cells did not cause significant changes in their growth density and morphology, indicating good biocompatibility of Bis-EFMA group (p > 0.05). The continuous margin proportion of the Bis-EFMA group was as good as commercial bulk-fill composites (p > 0.05). The sectional microhardness results showed that the Bis-EFMA group had the highest microhardness. After the friction and wear test, the volume wear of the Bis-EFMA group was minimal, indicating its good wear resistance and mechanical strength. Color changes in all resin groups after 28 days of immersion were within the clinically acceptable range. SignificanceThe addition of Bis-EFMA demonstrated excellent biocompatibility, edge adaptation and color stability comparable to commonly used clinical bulk-fill composites, along with preferable mechanical strength, friction and wear resistance. Bis-EFMA based bulk-fill composites have the potential to be employed as a bulk filling material in commercial dental composite applications.

Microstructure, mechanical properties and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x= 0, 0.5, 1.0) Y alloys

Microstructure, mechanical properties, and bio-corrosion behavior of Mg–2Zn-0.3Ca-x (x = 0, 0.5, 1.0) wt.% Y series alloy have been investigated using microstructure observation, microhardness testing, tensile testing, immersion tests, and electrochemical measurements in simulated body fluid (SBF). The results show that the second phase's type, volume fraction, and distribution change with Y microalloying in the Mg–Ca–Zn alloys. The Mg–2Zn-0.3Ca (alloy 1) mainly comprises α-Mg and Ca2Mg6Zn3 phases. However, the amount of the Ca2Mg6Zn3 phase gradually decreases, and phases I (Mg3YZn6) and W (Mg3Y2Zn3) are also formed in Mg–2Zn-0.3Ca-0.5Y (alloy 2) and Mg–2Zn-0.3Ca–1Y (alloy 3), respectively. Furthermore, an increase in Y content to 1% refines the grains of alloy 1 leading to the improvement of microhardness (66.7 ± 4.2 HV), yield strength (141 ± 7 MPa), and ultimate tensile strength (385.7 ± 18 MPa) in alloy 3. The coarse and discontinuous eutectic phases (α-Mg + Ca2Mg6Zn3) in alloy 1 leads to accelerating the galvanic corrosion near the grain boundary. Moreover, polarization tests show that the addition of the rare earth element Y up to 0.5% in the alloy 2 leads to decreased corrosion current density (4.04 × 10−3 A cm−2) and the best anti-corrosion property as the result of formation of a protective corrosion product film.

Effect of preheating before rolling on the microstructural and mechanical properties of lamellar Al/Ti/Al composite produced by roll bonding

This study explores the effect of preheating before rolling on the microstructural and mechanical properties of an AA5052/Ti/AA5052 lamellar composite fabricated by roll bonding. The roll bonding was done in two ways: conventional rolling and preheating before rolling. Preheating was done before rolling for 7 min at 350 °C. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness, and tensile tests were used for microstructural and mechanical investigations. By performing preheating, the strength increased from 468 MPa to 511 MPa, elongation changes were insignificant, and hardness decreased in aluminum and titanium layers from 108 to 100 HV and 234 to 212 HV, respectively. By preheating, aluminum diffusion in titanium and metallurgical connection occurred. Therefore, SEM showed better bonding in preheated specimens.

On the mechanisms of charge weld evolution in aluminum extrusion

This study aims to provide new insights into the governing mechanisms of material property evolution within the charge weld zone in the hot extrusion process of aluminum profiles. A set of 6xxx series aluminum alloy tubular profiles was produced through carefully designed industrial experiments of billet-to-billet extrusion. The evolution of material integrity within the charge weld zones was experimentally characterized by microhardness tests, optical microscopy, scanning electron microscopy (SEM), and drift-expansion tests. The experimental analyses reveal that the material integrity of charge welds gradually increases from the onset to the end, primarily driven by the ‘local’ pressure history experienced. Towards the end of the charge weld zone, grooves and holes, and oxide particles gradually vanish, leading to enhanced material integrity. A through-process finite element (FE) model was developed using QForm-Extrusion software to analyze the thermo-mechanical history of charge weld formation, providing a deeper understanding of how material properties evolve and the underlying mechanisms governing this evolution. The model was experimentally validated in terms of the extrusion load and distribution of the charge welds in extruded profiles. Overall, the new insights gained in this study offer valuable knowledge for enhancing the process and quality control in billet-to-billet extrusion, as well as reducing in-process scrap towards more sustainable production of aluminum profiles.

Effects of different LED light curing units on the degree of conversion and microhardness of different composites: FT-IR and SEM-EDX analysis

The aim of this study was to evaluate the degree of conversion (DC), Vickers microhardness (VHN), main components and surface properties of a microhybrid and two bulk-fill composite resins polymerized with second and third generation light emitting diodes (LED). Sixty cylindrical specimens of Filtek™ Bulk-Fill, everX Posterior (bulk technique) and Filtek Z250 (incremental technique) were prepared in plexiglass molds (5 mm in diameter and 4 mm in thickness) and cured with second-generation LED (Woodpecker LED.B) and third-generation LED (Valo) resulting in six groups (n = 10). DC was determined using Fourier transform infrared spectroscopy (FT-IR), and VHN with Vickers microhardness tester. The main components were identified by means of energy-dispersive X-ray spectroscopy (EDX) microanalysis; whereas filler particles and surface properties were analyzed by scanning electron microscopy (SEM). VHN and DC data were analyzed using two-way ANOVA, followed by t-test with Bonferroni correction for pairwise comparison (p < 0.05). When DC and VHN values were evaluated, after polymerization with second and third generation LED, there was a statistical difference in bulk-fill composites, while there was no statistical difference in microhybrid composite. While, the highest DC and VHN values were obtained after polymerization of Filtek Z250 with Valo, the lowest DC and VHN values were obtained with Filtek Bulk-Fill with Woodpecker LED.B. The degree of conversion and microhardness are affected by the structure of the composite resin and LEDs.

Copper metallization of carbon fiber-reinforced epoxy polymer composites by surface activation and electrodeposition

The application of polymer metallization in lightweight and high-strength materials for the sporting goods, automotive, aerospace and construction sectors has attracted considerable attention. The present study aims to deposit a thin, uniform copper (Cu) layer on an epoxy‑carbon fiber (epoxy-Cf) composite material for lightweight, high-frequency radio reflector applications (Ka-Band and higher frequencies) required in space missions. In this work, a surface-activated electroplating technique in which the surface of the substrate is activated with a Sn/Ag system, followed by conventional electroplating is studied. Surface activation deposits layers of conducting metal ions on the surface of the epoxy-Cf composite, which significantly improves the electrical conductivity of the composite surface. The subsequent electrodeposition takes place from a CuSO4 solution with a pH value of 4 at three different current density values of 0.05 A/dm2, 0.5 A/dm2 and 1 A/dm2. The presence and abundance of metallic Cu over epoxy-Cf composite were confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. The morphology and elemental composition of the coating were characterized by scanning electron microscopy equipped with energy dispersive spectroscopy. With current density and coating thickness, morphology of the deposit changed from cauliflower-like to spherical along with grain refinement. Microhardness test shows a hardness of 330 HV and the pull-off adhesion test gave a bond strength of 1.69 MPa for 27.56 μm thick copper deposit. A major challenge encountered during the deposition of Cu is the oxidation of the metal followed by immediate tarnishing. This issue has been effectively addressed by employing benzotriazole solution as a protective agent.

Tribological behavior of PDC-cutter including cemented carbide and polycrystalline diamond composites produced by HPHT for drilling applications

In this study, the tribological behavior of PDC-cutter including WC particles/Ta-20Nb binder composite as substrate and polycrystalline diamond composite as PCD layer produced by high pressure-high temperature (HPHT) for drilling applications was investigated. To examine the metallurgical behavior, phase analysis, hardness of substrate and PCD layer, and tribological behavior, scanning electron microscopy, X-ray diffraction, Vickers microhardness, and wear tests were used, respectively. Due to the HPHT of the manufacturing process, the high hardness of the interfaces, especially for the WC/Ta-20Nb was achieved, which had ∼28% higher hardness than the diamond grits/Ta-20Nb binder. Therefore, no obvious porosity was observed in the interfaces and the composites were completely densified because the particles had good retention strength. The wear results showed that the tribological behavior of PCD layer/granite or marble pairs was directly influenced by the binder content, with samples having a lower binder content showing superior wear performance. Additionally, worn surface investigations demonstrated that adhesive and abrasive wear mechanisms were present in all pairs, with their intensities being strongly correlated with the binder concentration.

A new experimental methodology for investigating the impact of subsequent welding passes on the properties of the austenitic stainless clad steel plates welded joint: part I – a substrate case study

In this study, the influence of the applying repeated thermal cycling during welding on the microstructural transformations and mechanical properties in Austenitic Stainless Clad-Steel Plates (ASCSP) has been investigated, particularly in the substrate. For this purpose, a novel methodology was used, by filling the entire groove length and gradually shortening the subsequent passes. Afterwards, microstructural characterization of different zones in the welded joint was conducted using optical microscope. Results showed a decrease in acicular ferrite (AF) in the Weld Metal Substrate (WM-S) from the root pass (10 kJ/cm) to the second pass (13.5 kJ/cm). This decrease continued until a total disappearance by the third pass due to a heat input of 17.8 kJ/cm. Vickers micro-hardness test was used to investigate the effect of the subsequent passes on the mechanical properties of the joint. Micro-hardness examination confirms the metallurgical results. It was revealed that micro-hardness variations are influenced by AF percentage and pro-eutectoid ferrite levels.

Study the Structure and Properties of TiO&lt;sub&gt;2&lt;/sub&gt;/HAp Coating onto Ti-6Al-4V Alloy Using Electrophoretic Deposition

In the present study, (TiO2/HAP) and TiO2 coatings were fabricated with electrophoreticdeposition on substrate for titanium alloy. This study aims to increase improve this alloyantibacterial properties by coating the surface with a bio ceramic (TiO2 and TiO2/HAP)nano-powders. Coating on Ti-6Al-4V with an electrophoretic deposition(EPD) technique,ideal conditions of 20V and a deposition time of (4 min). The surface properties of coatedsubstrates, such as, micro-hardness, surface roughness and wettability antibacterial test wereevaluated and compared to that of the uncoated substrate. The results showed that theelectrophoretic deposition is a favorable technique to make a bio coating on Ti-6Al-4Vsubstrate with excellent properties and structure for applications biomedical.The average micro-hardness of the TiO2/HAP coated sample is 1024 HV compared withthat of uncoated substrates is 80 HV. The average thickness of TiO2/HAP coating isdetermined to be (18µm) on the substrate surface at factor deposition time (4 min). The resultsof previous research indicate that the high wettability and surface roughness at the micronscale were for the synergistic effect of reduction on cell adhesion and growth.