Vickers Microhardness Measurements Research Articles

Experimental and theoretical investigation on the SR method grown semi-organic Piperazinium Tetrachlorozincate Monohydrate (PTZM) single crystal for optoelectronic applications

Efficient semi organic nonlinear optical (NLO) Piperazinium Tetrachlorozincate monohydrate (PTZM) [C4H12N2][ZnCL4]·H2O single crystals have been grown by slow evaporation solution technique (SEST) and Sankaranarayanan-Ramasamy (SR) method using water as solvent. Single crystal X-ray diffraction (SXRD) analysis reveals the unit cell parameters of the grown crystal. The morphology of the grown crystal was identified by the single crystal XRD analysis. The electrical properties, dielectric constant, dielectric loss and piezoelectric (d33) coefficient were determined. The etch pit density of PTZM crystal has been calculated by using the chemical etching analysis. The laser damage threshold (LDT) analysis was investigated by Nd: YAG laser and the wavelength of laser is 1064 nm. The mechanical stability of the grown PTZM crystal was studied using Vickers microhardness measurement. Utilizing quantum chemical calculations, the PTZM compound is analyzed for vibrational properties, HOMO and LUMO characteristics, NBO interactions, and the determination of first-order hyperpolarizability. The nonlinear susceptibility and first-order hyperpolarizability results provide compelling evidence and affirm the PTZM molecule’s potential as a strong candidate for nonlinear optical (NLO) applications.

Influence of intermetallic phase (TiFe) on the microstructural evolution and mechanical properties of as-cast and quenched Ti–Mo–Fe alloys

This study presents the phase analysis, microstructural characteristics, and mechanical property evaluation of the as-cast and quenched Ti–15Mo–xFe alloys with high iron content ranging from 4 to 12 weight percent. All the four alloys were produced in a vacuum-arc melting furnace. Heat treatment in the form of solution treatment was performed in a muffle furnace at a temperature of 1100 °C, with 1-h holding time and the samples were rapidly quenched in ice-brine. X-ray diffractometer (XRD) was used to analyses the phases present in each alloy whereas the optical microscope (OM) was employed to track the microstructural evolution and percentage porosity. The mechanical properties of the alloys were evaluated using a tensile test and compression test method while the micro-Vickers hardness measurements were conducted to evaluate hardness of the alloys. The XRD patterns of as-cast showed peaks belonging to the β and α″ phases and intermetallic B2 TiFe phases. The as quenched XRD peaks illustrated β phase only and Fe·Ti·O2 phases. The as-cast OM micrographs revealed equiaxed β grains, substructures, dendritic structure, and pores forming around the grain boundaries. The quenched OM showed only β equiaxed grains with pores throughout the grain boundaries. The tensile properties such as ultimate tensile strength (UTS) and elastic modulus (E) of as-cast TMF0 were 264 MPa and 79 GPa respectively and these properties changed upon quenching to 411 MPa and 66 GPa respectively. The elastic modulus of TMF1 in as-cast condition was 74 GPa. The UTS and E of TMF1, TMF2, and TMF3 in as-cast and quenched conditions were not recorded due to the fragility of the samples that failed prior to yielding any useful data. The compressive strength in as-cast and in quenched condition decreased with an increase in Fe content. The micro-Vickers hardness in as-cast and quenched conditions showed a similar trend with hardness increasing slightly upon quenching for TMF0, TMF1, and TMF3 alloys but slightly decreased in the case of TMF2. The fracture surfaces of all the as-cast and quenched alloys were comprised of ductile and brittle fracture.

Mechanical properties of Ag-added DyBa2Cu3Oy superconducting melt-textured bulks prepared by the single-direction melt growth method

Ag-added DyBa2Cu3Oy superconducting melt-textured bulks were prepared using the newly developed single-direction melt growth (SDMG) method with different pre-heat-treatment conditions. Clearly distinct microstructures were observed depending on the pre-heat-treatment conditions and thickness of the bulks. Their mechanical properties were evaluated by use of Vickers microhardness measurements at varying applied forces. Vickers microhardness increases with an increase in the applied force for each sample, up to an importantly high value of ∼9 GPa at the saturated region, indicating all the prepared bulks demonstrate the untypical reverse indentation size effect (RISE) performance. In addition, the experimental results found from the saturation regions are examined by the mechanical methods such as Meyer's law, proportional sample resistance model, elastic/plastic deformation, Hays-Kendall (HK) approximation, and indentation-induced cracking (IIC) model. According to the mechanical modelling findings, the HK and IIC models are found as appropriate mechanical models describing the hardness values for all the studied bulks exhibiting RISE feature and the true values are suggested to lie between the estimated values of HK and IIC models.

Enhanced Microhardness and Corrosion Performance of Additively Manufactured Inconel 718 Specimens through Nanostructuring by Severe Plastic Deformation

Severe plastic deformation (SPD) processes, particularly high-pressure torsion (HPT) have been increasingly applied to metallic specimens fabricated by laser powder bed fusion (L-PBF) additive manufacturing (AM) for enhancing their mechanical and functional properties through nanoscale grain refinement (≤ 100 nm). In this study. L-PBF AM-fabricated Inconel 718 (IN 718) specimens are initially subjected to 10 HPT revolutions to produce nanosized grains. Subsequently, microstructural characterisation, as well as hardness and electrochemical tests are conducted to evaluate the evolution of microstructures, hardness, and corrosion performance of the as-received and HPT-processed specimens by using various microscopy, Vickers microhardness (HV) measurements, and corrosion performance, respectively. The results reveal an average grain size of ~ 46 nm, dense dislocation networks, and nanotwins after 10 HPT processing, which contribute to the two-fold hardness increase compared to the as-received condition. Such microstructures also contributed to the overall improved corrosion performance after 10 HPT processing, as quantified by the 83% and 73% reduction in corrosion rate and pitting potential, respectively.

Effect of nano-Al2O3 particle addition on Co–P–xAl2O3 nanocomposite plating electroplated on X65 steel

PurposeThe purpose of this study is to reveal the effect of nano-Al2O3 particle addition on the nucleation/growth kinetics, microhardness, wear resistance and corrosion resistance of Co–P–xAl2O3 nanocomposite plating.Design/methodology/approachThe kinetics and properties of Co–P–xAl2O3 nanocomposite plating prepared by electroplating were investigated by electrochemical measurements, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Vickers microhardness measurement, SRV5 friction and wear tester and atomic force microscopy.FindingsA 12 g/L nano-Al2O3 addition in the plating solution can transform the nucleation/growth kinetics of the plating from the 3D progressive model to the 3D instantaneous model. The microhardness of the plating increased with the increase of nano-Al2O3 content in plating. The wear resistance of the plating did not adhere strictly to Archard’s law. An even and denser corrosion product film was generated due to the finer grains, with a high corrosion resistance.Originality/valueThe effect of different nano-Al2O3 addition on the nucleation/growth kinetics and properties of Co–P–xAl2O3 nanocomposite plating was investigated, and an anticorrosion mechanism of Co–P–xAl2O3 nanocomposite plating was proposed.

Archaeometallurgical Study of a 16th–17th Century “Rapier” Sword Manufactured in Caino (Northern Italy)

AbstractA metallurgical study was performed on a 16th–17th century “rapier” sword manufactured in Caino (northern Italy). Metallographic investigations and Vickers microhardness measurements indicate that the rapier was forged by assembling via hammer-welding different hypoeutectoid and near eutectoid steel bars. The rapier blade was heat treated by slack-quenching to increase its hardness, especially near the blade tip, improving the thrusting performance. The chemical composition of slag inclusions was analyzed by scanning electron microscopy coupled with X-ray dispersive spectroscopy. Compositional data of slag inclusions were analyzed by a multivariate statistical strategy aimed to distinguish and classify slag inclusions on the basis of their origin. It was estimated that the temperature reached during the finery and forging processes was at least 1270 °C and 1160 °C, respectively.

The Effects of Layer Thickness on the Mechanical Properties of Additive Friction Stir Deposition-Fabricated Aluminum Alloy 6061 Parts

Solid-state additive friction stir deposition (AFSD) is a thermomechanical-based additive manufacturing technique. For this study, AFSD was utilized to produce aluminum alloy 6061 (AA6061) blocks with varying layer thicknesses (1 mm, 2 mm, and 3 mm). The mechanical properties were assessed through uniaxial tensile tests and Vickers microhardness measurement, and statistical analysis was employed to investigate differences among data groups. The results revealed that the deposition layer thickness influences tensile properties in the building (Z) direction, while the properties in the X and Y directions showed minor differences across the three AFSD blocks. Furthermore, variations in tensile properties were observed depending on the sample orientation in the AFSD blocks and its depth-wise position in the part in the building direction. The microhardness values decreased non-linearly along the building direction, spread across the width of the part’s cross-section, and highlighted that the deposition layer thickness significantly affects this property. The 1 mm block exhibited lower average microhardness values than the 2 mm and 3 mm blocks. The temperature histories and dynamic heat treatment are influenced by the deposition layer thickness and depend on the location of the point being studied in the part, resulting in variations in the microstructure and mechanical properties along the building direction and across the part’s width.

Influence of Heat Treatment Parameters on the Microstructure of 17-4 PH Single Tracks Fabricated by Direct Energy Deposition

Post-fabrication heat treatment (PFHT) is one of the most applied strategies for achieving the desired microstructure and mechanical resistance on additive manufactured components because of the non-equilibrium microstructural state of the material in the as-built condition. In particular, during PFHT, 17-4 PH martensitic stainless steel is mainly strengthened by the precipitation of Cu-rich nanometric particles and Nb carbides into the metal matrix. In this work, the influence of specifically designed PFHTs on the microstructural and mechanical properties of 17-4 PH single tracks fabricated via direct energy deposition was studied. Different solubilization and aging times, as well as a direct aging strategy, were considered. Optical microscopy, X-ray diffractometry, and transmission electron microscopy were used to investigate the microstructure evolution induced by the PFHTs. Moreover, Vickers microhardness measurements were performed to evaluate the increase in mechanical strength. In all cases, the heat-treated single tracks showed a mean microhardness higher than that of the depositions in the as-built condition. In the single tracks subjected to solution treatment, followed by aging for about 100 h, the presence of both Cu-rich precipitates and Nb carbides was assessed; conversely, when directly aged from the as-built condition, only Nb carbides were detected. In the latter case, the carbides were finer and closer to each other than those in the single tracks aged after the solution treatment.

Interfacial characteristics of multi-material SS316L/IN718 fabricated by laser powder bed fusion and processed by high-pressure torsion

This study focuses on investigating the microstructure and mechanical properties across the interface of a multi-material, Austenitic Stainless Steel 316 L (SS316L) and Inconel 718 (IN718), fabricated using laser powder bed fusion (LPBF) additive manufacturing (AM) technique. Challenges such as distortion, porosity, and intermetallic formation are common in such structures. To address these challenges, high-pressure torsion (HPT), a severe plastic deformation (SPD) process, was employed to eliminate porosity and create a homogeneous microstructure. The samples underwent HPT with varying numbers of turns, namely quarter, half, one, five, and ten turns, at room temperature and under 6 GPa of pressure at a speed of 1 rpm. The process aimed to create ultrafine and nano-grains in the microstructure and reduce the defects. A comprehensive characterization approach was adopted to analyze the interface. The results showed reduced porosity, improved bonding, and enhanced material density through HPT. X-ray diffraction (XRD) analysis confirmed the retention of the austenitic face-centered cubic (FCC) phase in both materials. The dislocation density reached a saturation point of 1.85 × 1015 m−2, while the crystallite size decreased to 26 nm. Transmission electron microscopy (TEM) analysis provided insights into the microstructure, showing dislocation networks at lower torsional strain and homogenous nano-grains at higher torsional strain. Vickers microhardness and nanoindentation measurements demonstrated an increase in hardness with increasing torsional strain, with the peripheral region exhibiting rapid hardness saturation and the central region showing lower hardness due to reduced strain. Overall, this study provides valuable insights into the effects of HPT on multi-material SS316L/IN718, contributing to the understanding of their interfacial characteristics and enhanced utilization of multi-materials in various engineering applications.

Change in Mechanical Properties of Laser Powder Bed Fused AlSi7Mg Alloy during Long-Term Exposure at Warm Operating Temperatures.

Al-Si-Mg alloys are most commonly used to produce parts by laser powder bed fusion for several industrial applications. A lot of papers have already focused on the effects induced by conventional heat treatments on the microstructure and mechanical properties of AlSi10Mg alloys, rather than on AlSi7Mg. Nobody has investigated thermal stability during long-term direct and artificial aging heat treatments of AlSi7Mg. This study investigates the changes in mechanical properties induced by long-term exposure (512 h) at 150 and 175 °C (the operating temperature of AlSi7Mg) after (i) the laser powder bed fusion process performed on a pre-heated build platform (150 °C), and (ii) heat treatments to the solution at 505 °C per 0.5 and 4 h. Thermal stability was evaluated through both Vickers microhardness measurements to obtain the aging profiles, and tensile tests to evaluate the mechanical properties in specific conditions. An optical microscope was used to investigate the microstructure. It was found that aging at 175 °C confers the same effects induced by a secondary aging heat treatment on as-built samples and, simultaneously, the worst effects on the solution heat treated AlSi7Mg alloy after long-term exposure. The AlSi7Mg DA at both 150 °C and 175 °C showed the same Vickers microhardness (~95 HV0.5), UTS (~300 MPa), and YS (~200 MPa) values for the longest exposure times because the fine and cellular α-Al matrix confers higher stiffness and strength despite the over-aged conditions. On the other hand, the coarsening effects that affected the precipitates during aging at 175 °C, as well as the formation of the precipitate-free zones along the grain boundaries, justified the highest detrimental effects induced on the SHTed samples.

Development of Multi-Component B-C-N Diffusion Coating on Wrought AISI M2 High-Speed Steel Substrate

The present investigation has been carried out to study the microstructure evolution and microhardness of the multi-component B–C–N diffusion coatings developed on wrought AISI M2 high-speed steel substrate at 560 and 650 °C for 1 and 4 h for both temperatures. The microstructure of the coatings was studied using scanning electron microscopy, energy dispersion spectroscopy and X-ray diffraction analysis. Vickers microhardness measurements were also performed. The investigations showed that varying conditions of the thermochemical treatment resulted in a variety of coatings which exhibited varying microstructure, phase composition and microhardness.

High-speed laser cladding: new developments for wear and corrosion protection

Fusion-bonded and low-diluted overlay welded coatings are frequently very thick (>1mm), which results in high material consumption (kg/m2) and expenses. High-speed laser cladding is a novel process, which can produce thin fusion-bonded and low-diluted coatings with high coverage rates and low heat input. Coating materials utilized in high-speed cladding have varied from soft Ni-based superalloys to harder martensitic stainless steels and base materials from low alloy steels to austenitic stainless steels. The ultimate objective has been to develop crack-free alternatives to environmentally hazardous hard-chrome plating. In this paper, high-speed laser cladding was used to fabricate relatively thin Ni-based coatings on various cast irons for corrosion protection and Ni-based hard-faced coatings reinforced with chromium (Cr3C2) and tungsten carbides (WC/W2C), for the first time, onto low-alloy structural and quenched & tempered steels for wear applications. Obtained coatings were characterized with X-ray diffraction (XRD), optical (OM), and scanning electron microscopy (SEM). Corrosion performances were explored in long-term salt spray tests. Mechanical and wear properties were tested with Vickers microhardness measurements and three-body dry-sand rubber wheel abrasion tests (RWAT). It was shown that soft low-diluted Ni-based coatings protected the cast iron base materials in salt spray tests. Ni-based hard-faced coatings with hardness up to 1200 HV1 exhibited high wear resistance in low-stress three-body abrasion better than hard-chrome plated coating, which was attributed to the high volume fraction of hard carbide reinforcements.

Effect of Sn Addition on the Microstructure and Age-Hardening Response of a Zn-4Cu Alloy

The aim of this research is to assess the influence of Sn inclusion on the microstructure evolution and age-hardening response of a Zn-4Cu alloy. This is the first study to correlate the age-hardening response to the microstructure of Zn-4Cu alloy reinforced with different Sn contents. A series of Zn-4Cu-Sn alloys were successfully fabricated with different Sn concentrations in the range of 0.0–4.0 wt.% using permanent mold casting. The microstructure of Zn-4Cu-Sn alloys was investigated by means of a scanning electron microscope (SEM) attached with an energy dispersive spectroscope (EDS) and X-ray diffraction (XRD) line profile analysis. At room temperature, the Vickers microhardness measurements were used to assess the age-hardening response of alloys. The results show that the microhardness of the Zn-4Cu (ZC) binary alloy increases a little bit from 76 to 80 HV as the aging time increases from 2 to 128 h, respectively. For aging times up to 16 h, the microhardness of all Sn-containing alloys decreases but then increases again. The lowest hardness belongs to the ZC-1.5Sn alloy, and the Sn-Zn-3.0Sn alloy has the highest; the other alloys fall somewhere in between. At high aging times (64 and 128 h), the microhardness of all Sn-containing samples increased continuously with an increasing Sn content from 0.0 to 3.0 wt.%. When the Sn-containing alloys (3.5 and 4.0 wt.% Sn) were aged for 64 and 128 h, the hardness declined by 7.94% and 8.90% compared to their peak aging hardness values, respectively. By considering the structural changes that occur in the Zn-4Cu-Sn alloys, the reasons for the observed variations in microhardness data with increasing Sn content and aging time were elucidated. X-ray diffraction (XRD) data was analyzed to determine the zinc matrix’s lattice parameters, c/a ratio, and unit cell volume variations.

ANALYSIS OF RESIDUAL STRESS BY X-RAY DIFFRACTION AND STUDY OF MICROSTRUCTURE IN WELDED JOINT OF ASTM A-36 MARINE STEEL

ASTM A-36 marine steel is one of the most used and classified as a medium strength carbon steel. Its characteristics and purpose are in common applications and in metallic structures in general, sawmills, walkways, agricultural machinery and implements, road, rail and oil implements. It is used in angles, round, flat and square bars and I, U and T profiles. In this work, 10 mm sheets, with a V chamfer, were welded using the MIG/MAG process and X-Ray Diffraction measurements were carried out to study of residual stresses caused by the welding process. Then samples were taken for metallography and microscopy in the Scanning Electron Microscope (SEM). They were also performed in the three regions of the weld: base metal (MB); thermally affected zone (ZTA) and in the molten zone (ZF) Brinell hardness tests, to determine the energy stored in the regions of the weld bead. Vickers Microhardness measurements were also made at the ZTA, as it is a very narrow range, to give more precision to the hardness measurements. The X-Ray Diffraction test showed that the air-cooled samples are compressive and the water-cooled samples are tensile. The micrographs of the samples, in the region of the weld, showed that the ferritic phase prevailed in the molten zone. It was also observed the precipitation of carbides and alloying elements, in addition to the presence of martensite. It is concluded, therefore, that the results for the MIG/MAG welding were satisfactory and recommended for the welding of ASTM A-36 Steel.

Comparison of Neutron Radiation Response of Conventionally Wrought Versus Additive Manufacturing Production Methods in Alloy 625

A point of study in the characterization of additive manufactured (AM) alloys is whether or not AM microstructure responds to external stimuli differently from conventionally manufactured alloys. Samples of Alloy 625, a nickel-based superalloy of interest, were produced by both additive manufacturing and conventional wrought methods. Samples of differing sizes were subjected to one of two different types of neutron fields during irradiation: fast neutron or reactor-spectrum neutron. Vickers microhardness measurements and transmission electron microscope images were used to analyze the differences between samples before and after they were subjected to the neutron fields. Results showed differing responses between the two fabrication methods.

YSZ–Al2O3 thermal barrier nanocomposites coatings: Electrophoretic deposition and characterization

AbstractThis paper presents the development of yttria‐stabilized zirconia–alumina (YSZ–Al2O3) nanocomposite coatings deposited on Inconel 738LC superalloy substrates using the electrophoretic deposition technique. To prepare stable suspensions of YSZ and Al2O3 nanoparticles, a mixture of 75 mL acetone and 25 mL ethanol was used as a medium with .4 g/L iodine as a dispersant. The effects of Al2O3 concentration on suspension stability, electrical conductivity, and pH were studied in detail to optimize the suspension chemistry. The deposition kinetics were systematically investigated as a function of suspension concentration, deposition voltage, deposition time, and iodine concentration () to optimize the process parameters. The as‐dried coatings deposited at Vd = 10 V for 90 s were uniform, crack‐free, and sintered at 1150°C for 4 h. The microstructure, phase composition, hardness, and adhesion strength of the coatings were analyzed using scanning electron microscopy, X‐ray diffraction, Vickers microhardness measurements, and conducting shear loading tests, respectively. The results showed that adding Al2O3 to YSZ reduces porosity, crack density, and sintering temperature while stabilizing the tetragonal phase and retarding the martensitic transformation and crack formation. Among the studied coatings, the YSZ–20 wt.% Al2O3 nanocomposite coating deposited at Vd = 10 V for 90 s exhibited the most improved microstructural features, hardness, and adhesion strength.

Mirrored symbols, opposite effects: Impact of Ga and Ag additions on the martensite decomposition of the Cu81Al19 alloy

Although the presence of martensite is desirable in several applications of increasingly complex Cu-rich Cu-Al alloys, there is a lack of understanding about the effects of alloying in its stability. Martensite decomposition was investigated in as-quenched Cu81Al19, Cu79Al19Ga2, and Cu79Al19Ag2 alloys (compositions in atomic percentage) by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry, and Vickers microhardness measurements. It was found that the similarity of crystalline structure between alloying element and host phase, as well as the interactions between ternary addition atoms and Al interfere with the stages of the martensite decomposition during heating. The Ga addition refined the microstructure, resulted in the precipitation of other phases, and favored the eutectoid reaction in the Cu81Al19 alloy. The Ag addition increased the tendency for martensite ordering, stabilized the β1 phase, and induced the precipitation of Ag particles from martensite on heating. Possible technological consequences arising from these results were also discussed.

Superconducting and Mechanical Properties of the Tl0.8Hg0.2Ba2Ca2Cu3O9−δ Superconductor Phase Substituted by Lanthanum and Samarium Fluorides

This study investigated the impact of samarium and lanthanum fluorides (SmF3 and LaF3) on the physical and mechanical properties of Tl0.8Hg0.2Ba2Ca2−xRxCu3O9−δ−yFy superconducting phases (specifically the (Tl, Hg)-1223 phase), where R = Sm and La, with 0.00 ≤ x ≤ 0.10. The superconducting samples were synthesized using the solid-state reaction method. X-ray diffraction (XRD) verified the formation of the (Tl, Hg)-1223 phase without altering its tetragonal structure. Scanning electron micrographs (SEM) reveal the improvement of the grain size and inter-grain connectivity as Sm and La contents increased up to x=0.025. The electrical properties of (Tl, Hg)-1223 were studied using I-V and electrical resistivity measurements. Improved superconducting transition temperature (Tc) and transport critical current density (Jc) were observed up to x=0.025, beyond which they decreased substantially. Vickers microhardness (Hv) measurements were performed at room temperature to investigate their mechanical performance with various applied loads (0.49–9.80 N) and times (10–90 s). For both substitutions, the mechanical properties were enhanced up to an optimal value at x=0.025. All samples exhibited normal indentation size effect (ISE) behavior. The proportional sample resistance (PSR) model best explained Hv values among five theoretical models. Dislocation creep was the primary creep mechanism in the samples, according to indentation creep studies.

Study of the Structural, Electrical, and Mechanical Properties and Morphological Features of Y-Doped CeO2 Ceramics with Porous Structure

In this work, ceramic samples of cerium oxide doped with yttrium were investigated. The concentration of a dopant Y(NO3)3 varied from 5 to 25 wt% in the initial charge. In the course of the experiment, a simple method was developed to obtain ceramics with a porosity of ~20% via one-step annealing in air in a muffle furnace. For comparison, samples with two annealings were also synthesized to determine the effects of pores on electrical, structural, and mechanical characteristics. The obtained samples were examined via X-ray powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy, dielectric spectroscopy, and Vickers microhardness measurements. The substitution of Ce4+ ions with Y3+ ions led to a significant decrease in the lattice parameter, average crystallite size, and average grain size, with a simultaneous increase in the lattice defectivity, dielectric constant, electrical conductivity, and microhardness values. It is shown that samples with a dopant weight fraction of 0.05–0.15 and one-step annealing have favorable electrical and mechanical characteristics for energy applications as porous materials with ionic conductivity.

Effect of Two Different Ultrafast Curing Exposure Durations on the Surface Hardness of Bulk Fill Composite - An In-Vitro Study.

The aim of the present study is to assess the microhardness of resin-based composites (RBCs) cured with ultrafast curing mode at two different exposure durations. This is an experimental in-vitro study. Forty-five cylindrical composite specimens were prepared to a dimension of 5 mm height and 4 mm diameter. Curing was done using three different exposure modes and duration with dual mode LED curing light as follows: Group I: Ultrafast curing mode for 1 second at 2300 mW/cm2 (n = 15); Group II: Ultrafast curing mode for 3 second at 2300 mW/cm2 (n = 15) and Group III: Standard exposure mode for 20 second at 1000 mW/cm2 (n = 15). Vicker's microhardness measurement was done on both the curing and non-curing sides of the specimen using a motorised diamond-faced micro-indenter (Wilson Wolpwert, Germany) using a load of 50 gram and a dwell time of 30 second. Kruskal Wallis ANOVA was used to test for difference between the three groups followed by Mann-Whitney U test for post-hoc analysis. The microhardness values of the composite cured with a conventional curing unit were significantly higher than the ultrafast cured specimens. Low-intensity conventional curing lights were found to perform better than the high-intensity ultrafast curing units.