Microhardness Tests Research Articles

Elaboration and characterization of Cu–Zn–Al shape memory alloys

AbstractThe study examines Cu–Zn–Al shape memory alloys, vital in aeronautics and automotive sectors. It aims to characterize their thermo-mechanical transformations induced by composition and heat treatments, focusing on how these impact mechanical properties, especially grain size refinement. Analysis covers transformation temperatures, micro-hardness, induced transformations, and mechanical tests. Results show thermoplastic martensitic transformations, with micro-hardness aiding in identifying characteristic points. The study's novelty lies in understanding how grain size refinement affects these transformations and the role of micro-hardness in precise characterization.

Evaluation of Flexural Strength and Vickers Micro Hardness of Three Different Denture Base Resin Materials

ABSTRACT Objectives: To evaluate the Vickers hardness and flexural strength of computer-aided design/computer-aided manufacture (CAD/CAM) milled, 3D-printed, and traditional heat-polymerized denture base resins used in computer-aided design and manufacture. Materials and Methods: A total of 60 samples were fabricated from CAD/CAM milled resin (PMMA dental material-Ruthinium disc, Badia Polesine (Rovigo) Italy), CAD/CAM 3D-printed resin (NextDent Denture 3D+, Soesterberg, The Netherlands) and conventional heat-polymerized (HP) denture base resin (DBR) (Triplex hot Ivoclar-Vivadent, Liechtenstein). Based on the three different denture base resin materials (n = 10/material) (30/flexural strength and 30/microhardness), the samples were split into six groups. The 3-point bending test was used to assess flexural strength, while Vickers microhardness test was used to assess surface hardness. The acquired data was statistically assessed. Results: CAD/CAM milled resins showed appreciably greater values for both the flexural strength and surface hardness, followed by conventional HP denture base resin and CAD/CAM 3D-printed resin. Pairwise comparison for Flexural Strength and Vickers microhardness revealed significant differences between groups. Conclusion: CAD/CAM milled resins had the highest surface hardness and flexural strength compared to Conventional HP denture base resin and CAD/CAM 3D-printed resin.

Development and Taguchi optimization of HVOF sprayed Al2O3 and ZrO2 blended aluminum coating on 316L SS

Abstract A significant number of gas turbines, aircraft engines, bearings, and automotive engines operating under a wide temperature range fail frequently due to fatigue and surface oxidation. Thus, a new coating formulation 40Al-35Al2O3-25ZrO2 was deposited on 316L SS substrate through the high velocity oxygen-fuel (HVOF) thermal spray coating method. The number of passes, spray distance and oxygen flow rate were varied by using Taguchi L9 array to achieve an optimized coating with higher hardness, less porosity, and roughness. The coating phase analysis, microstructure, elemental composition, microhardness and nano hardness were examined by X-Ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), Vickers microhardness and nano indentation testing. The sample 5 prepared at spray distance of 20 cm and oxygen/acetylene ratio of 2 exhibited optimal hardness (1972 HV1), tensile strength (6.463 GPa), porosity (0.75%) and roughness (6.2 µm) due to α-Al2O3 andt-ZrO2 phases. Oxygen flowrate was the influential parameter contributing 48.71% to microhardness and 42.41% to roughness, while spray distance with contribution 51.62% was influential parameter for porosity.

Smart piezoelectric composite: impact of piezoelectric ceramic microparticles embedded in heat-treated 7075-T651 aluminium alloy

AbstractSignificant advances have been made in material synthesis in the last two decades, with a focus on polymers, ceramics, metals, and smart materials. Piezoelectric-based smart materials generate an electric voltage in response to loads, enabling distributed monitoring in critical structural parts. Friction stir processing (FSP) is a versatile approach that can enhance material performance in various engineering fields. The primary objective of the current research is to examine the sensorial properties of heat-treated AA7075-T651 aluminium plates that have been included with Lead Zirconate Titanate (PZT) and Barium Titanate (BT) particles via FSP. This study includes a comparative analysis of sensitivities with AA5083-H111 self-sensing material, metallographic and physicochemical characterization, and an assessment of the mechanical properties impacted by the incorporation of piezoelectric particles. The sensitivity of AA7075-PZT was found to be significantly higher than that of AA7075-BT. AA7075-PZT achieved a maximum sensitivity of 15.27 × 10−4 μV/MPa while AA7075-BT had a sensitivity of only 7.28 × 10−4 μV/MPa, which is 52% lower. Microhardness and uniaxial tensile tests demonstrated that the presence of particles has an influence on both mechanical strength and electrical conductivity of aluminium components, as opposed to those that do not have particles. The complete investigation intends to give significant insights into the performance and prospective uses of these innovative smart materials, therefore advancing materials science and engineering. Graphical abstract

Tribological effects of varying volumetric energy density in additive manufacturing of inconel 718

Abstract This study investigates the novel effects of varying volumetric energy density (VED) ratios on the tribological characteristics of Inconel 718 alloy fabricated using Laser Powder Bed Fusion (LPBF) process. Nine VED ratios were investigated, and samples underwent non-contact surface roughness tests, Vickers microhardness tests, and residual stress analysis. Notably, this study identified specific VED conditions where superior wear resistance was achieved, contributing new insights into optimizing LPBF parameters for tribological performance. Based on preliminary analysis, samples 1, 3, and 8 were selected for ball-on-disc wear testing. Sample 8, fabricated with 330 W laser power, 50 mm/s scan speed, 0.10 mm hatch spacing, and 0.05 mm layer thickness, demonstrated superior tribological behaviour with a 32.12% and 52.11% lower friction coefficient and 31% and 29.92% less mass loss compared to samples 1 and 3, respectively. The presence of γ-Ni, γ’-Ni3 (Al, Ti), γ-FCC, and γ’-L12 phases, along with microstructural features such as columnar and cellular dendritic structures, were confirmed via SEM and X-ray diffraction analyses. This study’s novel findings contribute valuable knowledge for optimizing Inconel 718 production via LPBF, particularly in enhancing wear resistance through tailored VED settings.

Advanced neutron and [formula omitted]-ray shielding characteristics of nanostructured (90-x)Al-xGd2O3 composites reinforced by tungsten

This study introduces a composite material designed to offer exceptional mechanical strength and superior radiation shielding characteristics. By integrating tungsten into an aluminum Al-matrix with varying Gd2O3 content, we developed composites that meet the needful demands of mechanical durability and radiation protection in nuclear applications. The composites, synthesized via mechanical milling and sintering methods in planetary ball mills, have nominal compositions of (90-x)Al-xGd2O3 (x = 5, 10, 15 wt%) supplemented with 10 %W. The XRD analysis revealed phase structure transformations correlated with increased milling durations, while SEM-EDAX provided detailed morphological and elemental insights. TEM study confirmed a homogeneous distribution of nanocrystalline powders after 30 hours of milling while DSC thermographs indicated variations in thermal properties dependent on the Gd2O3 and tungsten content. The enhanced mechanical strength with higher concentrations of gadolinium and tungsten was characterized by Vickers microhardness tests. Neutron and γ-ray shielding properties were calculated using MCNP6.2 simulation code and Phy-X/PSD software. The thermal neutron macroscopic cross-section increased exponentially with higher Gd2O3 content, achieving values of 23.3 cm⁻¹ for 5 wt%, 48.4 cm⁻¹ for 10 wt%, and 73.7 cm⁻¹ for 15 wt%. Fast neutron removal cross-section also showed an increasing trend. The γ-ray linear attenuation coefficient decreased with increasing energy, but the Al-15Gd2O3-10 %W composite exhibited the highest LAC values, indicating superior γ-ray absorption capabilities. Correspondingly, the HVL values were lowest for the Al-15Gd2O3-10 %W composite. These findings demonstrate that Al-Gd2O3-W composites are promising materials for advanced industrial applications requiring robust mechanical properties and effective radiation shielding.

Influence of post-weld rolling and artificial aging on microstructure and mechanical properties of friction stir welded 2195-T4 Al-Li alloy joints

Fiction stir welding (FSW) of a naturally aged (T4) 2195 Al-Li alloy was conducted to study the effect of post-weld artificial aging (AA) and rolling+artificial aging (R+AA) on microstructure and mechanical properties of the FSW joints. Grain features were analyzed by electron back scattered diffraction (EBSD) technology, and precipitates were characterized using transmission electron microscopy (TEM) along [011]Al and [001]Al zone axes. Mechanical properties of the joints were evaluated through micro-hardness and tensile testing. The results indicate that grain development, including grain orientation, grain boundary components and dislocation density, varies within different regions of the As-welded joints due to complicated thermal-mechanical history. The alloying elements mostly exist as Guinier-Preston zones in the base material (BM) with a few formations of δ'/β', and slightly precipitate into T1 in the heat affected zone (HAZ), form σ in the thermal-mechanical affected zone (TMAZ), as well as develop T1 and S' in the nugget zone (NZ) after FSW. The lowest hardness zone (LHZ) exhibits elevated precipitation levels, generating coarse T1 and grain boundary precipitates with evident σ and precipitate free zone. The overall precipitation level of the As-welded joints remains minor, resulting in a slight decrease in hardness at the LHZ. Post-weld AA promotes many T1 formations, enhancing the joint strength and hardness. As a result, the ultimate tensile strength (UTS) of the joints increases from 440 MPa to 506.5 MPa, while the elongation decreases from 13.5% to 3.4%. Furthermore, hardness profiles transform from a low-amplitude wave curve to a high-amplitude W-shaped curve, generating a significant LHZ due to the minimal precipitation of T1. Pre-rolling deformation can enhance dislocation density and low angle grain boundaries (LAGBs), promoting the nucleation of high-density, fine T1 during artificial aging, and especially improves precipitation ability of the LHZ, leading to an elevated hardness increment in the region after AA. Compared to the Joint-AA, both strength and elongation of the Joint-R+AA increase, obtaining 530.5 MPa and 3.9%, respectively.

Impacts of the alloying elements and thermo-mechanical processing on the phase stability, crystalline structure, microstructure, and selected mechanical properties of Ti-(10-x)Al-xV (x = 0, 2, and 4 wt%) alloys targeted as external prostheses

This study aimed to characterize Ti-Al-V alloys submitted to thermo-mechanical processes and evaluate their impact on the crystalline structure, microstructure, coefficient of thermal expansion (CTE), selected mechanical properties, and cytotoxicity. X-ray diffraction (XRD) analysis revealed a major α phase, with V acting as a β-stabilizer. The cooling rate and the plastic deformation contributed to the formation of minor martensitic αʹ and β phases, with notable variations in cell parameters. The Energy-Dispersive XRD indicated the CTE was dependent on the alloying elements. Ti-10Al and Ti-8Al-2V depicted Widmanstätten laths and basket-weave structures, while Ti-6Al-4V showed typical features of β grain boundaries. Thermodynamic predictions aligned with the observed phase compositions. Vickers micro-hardness tests yielded values surpassing those of commercially pure titanium (CP-Ti), attributed to the synergistic effects of solid solution, phase precipitation, and strain hardening effects. And, elastic modulus approximated that of CP-Ti, largely due to the α phase's predominance. The solution treatment reduced the elastic modulus compared to the hot-rolled samples due to the stress relief and αʹ and β phase precipitation. Preliminary cytotoxicity assays confirmed the non-toxicity of the samples to cell viability. These findings suggest that the solutionized Ti-10Al sample is an economically viable candidate for fabricating external prostheses.

Disclosing Connection Links between Microstructure and Mechanical Performance in Pulsating Current Gas Tungsten Arc Welding of Hastelloy B-2 Superalloy

In this study, welding a Ni-Mo-based superalloy (Hastelloy B-2) was examined in order to characterize the microstructure and mechanical performance of joints along with assessing the effects of current intensity on the microstructure and mechanical responses of different weld zones. The gas tungsten arc welding (GTAW) process was used to weld the samples using ERNiCrMo-2 filler metal. The pulsed current GTAW process was used to weld the superalloy sheets of thickness of 1 mm with background current (Ib) of 20 A and 40 A and peak current (Ip) of 80 A and 60 A. Tensile and Vickers microhardness tests were conducted to evaluate the effect of pulsed current on mechanical properties of the welds along with chemistry and microstructure characterizations. Finally, the fracture surfaces after the tensile test were studied using SEM fractography analysis. The results indicated that increasing Ib and decreasing Ip led to low heat input and high cooling rate resulting in a high thermal gradient. This caused microstructure transition from the columnar dendrites to the coaxial ones in the weld zone; molten metal convection in the fusion zone led to fine grains in the weld zone during welding time. Moreover, a significant decrease in the amount of molybdenum carbides at the interdendritic regions of the weld metal was observed under these conditions. The tensile strength of the weld metal was higher than that of the base metal resulting in the fracture of all welds from the base metal. Additionally, the microhardness results indicated a significant increase for the weld metal compared to both heat-affected zone (HAZ) and base metal. The higher mechanical properties of the weld metal is attributed to the increase in background current and decrease in peak current leading to a fine grain microstructure. Fractography following the tensile test showed a completely ductile fracture.

The effect of cryogenic treatment on a high Co bearing DIN 1.2888 steel used as die in hot forging process

Abstract Hot work steels used as dies in metal forming processes must endure harsh conditions, typically achieved through a martensitic structure. However, retained austenite can persist after martensitic transformation, negatively impacting mechanical properties. Cryogenic treatment (CT) refines martensite, reduces retained austenite, and increases fine carbide density, thus enhancing performance. DIN 1.2888, a hot work tool steel with high cobalt content (~10%) and low carbon content (~0.2%), is less studied concerning the effects of CT. The objective of this study was to investigate how cryogenic treatment affects the mechanical and microstructural properties of DIN 1.2888 steel. Samples underwent conventional heat treatment (HT) and CT at -100, -140, and -180°C for 6 hours, followed by double tempering. Various analytical methods, including X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Vickers Microhardness tests, were used to examine the samples. Wear mechanisms were evaluated through pin-on-disc tests under different loads, and impact toughness was measured both at room temperature and the working temperature of dies (350°C). Results indicated that lowering the cryogenic treatment temperature resulted in a slight increase in hardness values from 507HV for the heat-treated sample to 529HV for the sample treated at -180°C. Additionally, the impact toughness improved significantly, with values rising from 12.35J for the heat-treated sample to 23.44J at 350°C for the cryogenically treated sample at -180°C. Wear rates also decreased by approximately 50%, particularly at higher cryogenic treatment temperatures. The improvement in wear resistance was attributed to finer carbide precipitation and a more homogeneous distribution of carbides. These findings suggest that deep cryogenic treatment has a positive effect on DIN 1.2888 steel by decreasing retained austenite and increasing fine carbide density, leading to enhanced mechanical properties and extending the lifespan of the steel in die applications.

Boronize Coatings Studied with a New Mass Transfer Model.

This study examined the development of Fe2B (diiron boronize) coatings on the surface of 35NiCrMo4 steel through the thermochemical surface hardening process called boronizing. The morphology and thickness of the boronize coatings were assessed using Scanning Electron Microscopy (SEM) and optical microscopy (OM). A novel mathematical mass transfer model was developed to estimate the diffusion coefficients of boron in hard coating. The presence of uniformly distributed boronize coatings with a typical sawtooth pattern on the surface of the substrate was confirmed. The boronize coating's chemical composition and phase constituents were analyzed utilizing X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The study confirmed the presence of a single-phase boronize coating (Fe2B). Furthermore, microhardness tests indicated that the boronized specimen's surface demonstrated an average hardness of approximately 1953 HV. The wear study were conducted using the pin-on-disk method under dry debonding conditions at room temperature to estimate the coefficient of friction (COF) of the boronized (average ≈ 0.35) and untreated (0.725) specimens. The results revealed approximately 200% improvement in wear resistance due to the boronized coating. The empirical validation of the mathematical model was carried out for two additional boronizing conditions at 1223 K for 3 h and 1273 K for 1.5 h, resulting in an estimated percentage error of around 2.5% for both conditions. Additionally, an ANOVA analysis was performed, taking into account the temperature and time factors. The findings indicate that both factors exert a substantial influence on the dependent variable (u), with temperature (T) contributing 64.68%, time (t) contributing 27.37%, and the interaction of both factors (T × t) contributing 5.13%.

Effects of Various Solutions on Color Stability and Surface Hardness of Nanohybrid Dental Composite Under Simulated Oral Conditions.

This study evaluated effects of various solutions on color stability and surface hardness of a nanohybrid dental composite in simulated oral environments. Sixty-four composite disks were fabricated and randomly allocated into eight groups (n = 8 per group): Artificial saliva (AS), Biotene (B), passion fruit juice (PFJ), orange juice (OJ), Sprite (S), Coca-Cola (CO), apple cider vinegar (ACV), and cranberry juice (CJ). Specimens were immersed in respective solutions at 37°C for 28 days. Surface microhardness was assessed using Vickers microhardness test, and color alterations were quantified using SpectroShade Micro spectrophotometer. Measurements were taken 24 hours after initial polymerization and after 28-day immersion period. Statistical analysis was performed using mixed model ANOVA. After 28 days, specimens exhibited significant changes in microhardness and color. Polished surfaces showed microhardness decreases of 21.9-35.5%, with ACV and CJ causing largest reductions. Non-polished surfaces unexpectedly showed increased microhardness (11.2-17.4%). Color changes were more pronounced on polished surfaces, with CO and CJ causing maximum alterations. Statistical analysis revealed significant interactions between surface treatment, staining media, and immersion time (p < 0.05). All experimental groups demonstrated significant changes, highlighting composite materials' susceptibility to environmental factors. Even well-polymerized and polished surfaces underwent alterations, emphasizing necessity for periodic follow-up and maintenance polishing in esthetic restorations. The present research emphasizes significance of oral environmental factors on composite restoration longevity and esthetics, advocating for patient education on dietary impacts and tailored maintenance strategies to preserve restoration quality. How to cite this article: Shetty P, Jayakumar HDN, Pulickal TJ, et al. Effects of Various Solutions on Color Stability and Surface Hardness of Nanohybrid Dental Composite Under Simulated Oral Conditions. J Contemp Dent Pract 2024;25(7):669-676.

Tribological and corrosion characteristics of aluminium–copper alloys reinforced with alumina nickel aluminide cermet powder

Aluminium–Copper (Al-10Cu) alloys are widely used for structural components in the aviation sector. This study focuses on the synthesis and characterisation of Al-10Cu alloy reinforced with Al2O3-30(Ni-20Al) cermet particles to evaluate their microstructural, mechanical, tribological and corrosion properties. The Al-10Cu alloy was cast with varying percentages of cermet (2% and 4%) using a controlled casting process. Comprehensive microstructural analyses, including optical microscopy, SEM and EBSD, were performed to assess the grain structure and cermet distribution. The mechanical properties were evaluated through Vickers microhardness and tensile testing, while tribological performance was assessed using a Pin-on-Disc tribometer. Corrosion resistance was investigated through exfoliation and immersion corrosion tests. The results indicated significant improvements in microhardness and wear resistance with the addition of cermet particles, while the tensile strength showed a complex interplay between ductility and brittleness. Corrosion tests revealed enhanced resistance in cermet-reinforced specimens. This study demonstrates the potential of Al2O3-30(Ni-20Al) cermet as an effective reinforcement for aluminium alloys to achieve superior performance in structural applications.

Effects of deposition strategies on microstructure and mechanical properties of wire arc additive manufactured CoCrFeNiMo0.2 high-entropy alloy

High-entropy alloys (HEAs) have great potential for application in various fields due to their excellent performance. However, there are few reports on wire arc additive manufacturing of HEAs. In this study, CoCrFeNiMo0.2 HEA solid wire was prepared and used for WAAM based on cold metal transfer for the first time. Different deposition strategies (namely single-pass (SP), oscillation (OS), and multi-parallel pass (MPP)) were used to prepare metal wall samples of different thicknesses. The HEA samples' microstructure with different deposition strategies were explored by optical and scanning electron microscopy, as well as the electron backscatter diffraction method. Microhardness and tensile tests were used to evaluate the mechanical properties of different samples. The results prove that SP and MPP samples exhibit rougher surfaces due to heat accumulation. The OS sample has the best molding and an effective deposition ratio of up to 91.5 %. The composition of columnar grain grown along the deposition direction with strong {100}<001> cubic texture in both SP and OS samples. Therefore, these two samples have similar mechanical properties, and the mechanical performance in the vertical direction is better than that in the horizontal direction. Due to the complex internal thermal effects and remelting effects between welds, the internal structure of the MPP sample exhibits no obvious preferred orientation. Therefore, the anisotropy of mechanical properties is significantly alleviated.

Optimizing weld strength and microstructure in CP-titanium and 304 stainless steel friction welds with chromium interlayer

This study investigates the effect of a Cr-interlayer on the hardness and friction-welded joint strength between CP-titanium and 304 stainless steel. Rotary friction welding, with its adjustable parameters such as upset pressure, is the preferred method for this dissimilar joint. Due to the difference between these two base metals, a metallic interlayer like chromium, is crucial for controlling the formation of intermetallic compounds (IMCs). Welding was conducted at three different upset pressures, both with and without the Cr-interlayer. Tensile and microhardness tests were performed, complemented by phase analysis and microstructural characterization using XRD and SEM. Our findings reveal that employing a chromium layer and higher upset pressures enhances strength while reducing the presence of brittle IMCs in the welds. At the CP-titanium side, dynamic recrystallization occurs due to increased heat generation at the interface and strain occurred by materials flow, facilitating IMC formation, especially evident at 250 MPa upset pressure. Interestingly, relatively higher strength at 150 MPa is attributed to the absence of IMCs. Conversely, higher strength results at 350 MPa due to from the flow of softened material, effectively purging IMCs from the weld zone. Notably, both β-titanium and chromium-based IMCs form in the presence of the chromium interlayer, resulting in decreased joint hardness and increased overall ductility. In conclusion, our study's findings contribute to bridging the gap between theoretical strength and practical application, significantly advancing joint performance.

Analysis of Stress Corrosion Cracking Growth Rate in the Heat-Affected Zone of 316L Based on the Heterogeneity of the Mechanical Properties

The heterogeneity of the microstructure and mechanical properties of safe-end dissimilar metal welded joints (DMWJs) presents a challenge to the quantitative prediction of the stress corrosion cracking (SCC) growth rate directly from laboratory data. This study investigates the effect of the heterogeneity of the mechanical properties of the 316L-welded heat-affected zone (HAZ) in safe-end DWMJs on the SCC tip stress-strain field and the SCC growth rate. First, based on the analysis of microstructures in localized regions within the 316L-welded HAZ and the acquisition of material mechanical properties through microhardness testing, a user-defined material subroutine was developed to characterize the heterogeneous material properties within the 316L-welded HAZ. Then, using this finite element model with an inhomogeneous distribution of the mechanical properties of the material, the crack tip strain rates (CTSRs) at different locations within the 316L-welded HAZ were obtained. In conjunction with the FRI model, the SCC growth rates at various locations within the HAZ were determined. The results show that the closer to the 52Mw/316L fusion boundary within the 316L-welded HAZ, the greater the yield strength of the material and the higher the CTSR and predicted SCC growth rates at the characteristic distance.

The Effect of Human Blood and Platelet-rich Fibrin on the Surface Microhardness of Hydraulic Calcium Silicate-based Cements

Objectives: This study aimed to compare the effect of human blood and platelet-rich fibrin (PRF) on the surface microhardness of hydraulic calcium silicate-based cements (OrthoMTA and RetroMTA). Materials and Methods: Two types of mineral trioxide aggregate, OrthoMTA and RetroMTA, were mixed and placed into cylindrical molds. The lower surfaces of all cements were exposed to saline. The upper surfaces of cements were exposed to human blood, PRF, or phosphate buffer saline (PBS). After storage for 7 days in fully saturated humidity at 37°C, the microhardness of cement surface exposed to blood, PRF, or PBS was measured using the Vickers microhardness test. The data were analyzed using two-way analysis of variance and post hoc Tamhane’s T2 test. The significance level was set at P&lt;0.05. Results: Exposure to blood and PRF significantly decreased the surface microhardness of OrthoMTA and RetroMTA. The microhardness of PBS-contacted cements was significantly higher than that of blood or PRF groups (P&lt;0.001). The microhardness values for OrthoMTA exposed to PRF were significantly higher than the blood group (P=0.020). There were no significant differences between RetroMTA contacted with blood or PRF groups (P=0.985). When exposed to blood or PBS, RetroMTA had a significantly higher microhardness than OrthoMTA (P&lt;0.001 for blood, P=0.002 for PBS). Conclusion: Exposure to blood or PRF decreased the surface microhardness of both cements. Blood-contaminated RetroMTA showed significantly higher surface microhardness than OrthoMTA contacted with blood. No significant difference was found between PRF-contacted OrthoMTA and RetroMTA.

Comparative Evaluation of Ion Release and Uptake of Fluoride Varnish Containing Dicalcium Phosphate Dihydrate and Casein Phosphopeptide-Amorphous Calcium Phosphate – An Experimental Approach.

The effectiveness of fluoride varnish may be restricted due to inadequate bioavailability of phosphate and calcium ions in the oral cavity. Dicalcium phosphate dihydrate and Casein phosphopeptide–amorphous calcium phosphate have exhibited ability to enhance absorption of calcium and fluoride. The present study aims to compare the remineralization potential of fluoride varnishes containing DCPD and CPP-ACP. Materials and Method: The ion release, precipitation and surface microhardness of enamel blocks were compared following topical application of various Floride varnishes. Thirty enamel blocks were divided into 3 groups following randomization that included: NaF varnish (Group A), CPP-ACP NaF varnish (Group B) and DCPD- NaF varnish (Group C). Pre- and post-treatment microhardness was evaluated using Vickers Microhardness Tester. UV-Vis Spectroscopy assessed the fluoride release at 2 hrs, 4 hrs and 6 hrs. The uptake of fluoride, calcium and phosphates were determined using SEM-EDX. The statistical significance was tested with One-way ANOVA variance for normality followed by post-hoc tests (p ≤ 0.05). Results: All the groups showed statistically significant increase in microhardness post-treatment (Group A: p=0.03, Group B, C: p=0.00). The mean increase in VHN was Group B (53.67) &gt; Group C (34.75) &gt; Group A (27.40). No significant difference in the F release was noted over time (p=0.00). The fluoride release over all three time intervals was Group C &gt; Group B &gt; Group C. Fluoride, Calcium and Phosphates showed highly significant differences between groups (p=0.00) with Group C &gt; Group A&gt; Group B. Conclusion: The novel NaF-DCPD Varnish displayed a promising remineralization potential, however it cannot be conclusively considered to be superior to the commercially available NaF-CPP ACP Varnish. Further in-vivo investigations need to be undertaken to determine the efficacy of NaF-DCPD varnish to determine its feasibility in clinical practice.

Surface modification of high-speed steel (HSS) drills by plasma nitriding and cathodic cage tin deposition

Cutting tools made of high-speed steel have significant economic and technological importance. To enhance their productivity, thermochemical treatments are sought to improve both surface mechanical and tribological properties. Plasma nitriding and thin film deposition are widely employed for this purpose. In this study, modifications were made to M2 high-speed steel drills through plasma nitriding at temperatures of 400°C and 450°C. Cathodic cage TiN plasma deposition was also performed, varying the dwell time at a fixed temperature of 450°C. Characterization techniques included optical microscopy, X-ray diffraction (XRD), Vickers microhardness testing, and scanning electron microscopy (SEM). Performance tests were carried out to evaluate the behavior of the drills in relation to wear when machining AISI 1020 steel. It was observed that longer deposition times promote more uniform and thicker layers, and higher nitriding temperatures result in thicker nitride layers. An increase in hardness was noticeable in all deposition and nitriding treatments, with the nitrided samples exhibiting the highest hardness. During performance tests, the cathodic cage plasma TiN deposition demonstrated greater potential for application in HSS drills, with a treatment lasting 4 h providing the best results.

Effects of Electromagnetic Field on Microstructure and Properties of Ni‐ Based Coatings Reinforced by WC in‐Situ

The in situ WC‐reinforced Ni60 laser cladding layer‐assisted electromagnetic field is prepared on the H13 steel surface. The microstructure and phase of the cladding layer are analyzed by scanning electron microscope, energy disperse spectroscopy, and X‐ray diffractometry, the hardness and wear resistance of the coating are tested by microhardness tester and ring‐block friction and wear tester. The results indicate that more WC particles are generated with the increase in the magnetic field strength and current value, and many uniformly distributed eutectic carbides are formed in the coating, which makes the structure more uniform and dense. The average microhardness of the coating reaches 786.5HV when the electromagnetic intensity is 20 mT‐9 A, and the wear amount after 90 min is 35.2 mg, which is 65.7% of the nonelectromagnetic‐assisted WC/Ni60 coating and only 28.6% of the substrate, the wear resistance is obviously improved. The change in the structure and the improvement in microhardness and wear resistance are the result of the combined action of the directional Lorentz force generated by the electric field and the inductive Lorentz force generated by the magnetic field.