Dynamic Ultra-micro Hardness Tester Research Articles

Mechanical strength measurement of needle-shaped CaSO4 microcrystals by a three-point bend test

A simple method for direct measurement of the mechanical strength of needle-shaped microcrystals of calcium sulfate, CaSO4, is proposed. The microcrystals, with a length from 30 to 50 μm and transverse dimensions from 1 to 3 μm, can act as reinforcing filler in various structural and building composites to improve their mechanical properties. The method is based on a three-point bend test, adapted to microscopic objects. The CaSO4 microcrystals were placed on a substrate, which was a twill-weave filter mesh consisting of intertwined steel fibers with diameter of ∼25 μm. Due to the twill weave, the mesh surface is characterized by a periodic distribution of protrusions and depressions. The protrusions act as supports for the placing of microcrystals, and the depressions provide the possibility of deformation and destruction of microcrystals under the action of an increasing vertically acting force, which is applied to the microcrystal through the indenter of the dynamic ultra-micro hardness tester. The moment of destruction of the microcrystals is observed to be dependent on the force on the displacement of the indenter. The measured values of the mechanical strength of CaSO4 microcrystals varied in a range from ∼3.5 to ∼6.0 GPa. The experimental strength values are in good agreement with the values obtained from the results of numerical analysis of the stressed state formed in the volume of CaSO4 microcrystals during the three-point bend test.

Influence of carbon target power on the tribological and electrochemical properties of NbMoSiC composite films in seawater

Because the wear and corrosion of marine engineering equipment will cause huge economic losses to enterprises every year, thus it is necessary to develop advanced protective films to ensure the normal operation of marine equipment. Here NbMoSiC composite films are deposited using DC magnetron sputtering in an argon atmosphere through varying the carbon target sputtering power, and their microstructure and mechanical properties are investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS)，Raman spectroscopy and dynamic ultra-micro hardness tester, respectively. The tribological properties of the films in air and artificial seawater are determined by a reciprocating ball-on-disc tester, while the electrochemical properties of the films in seawater were evaluated by an electrochemical workstation. The results demonstrate that the presence of Nb2C, MoSi2, free silicon, and amorphous carbon (a-C) in the NbMoSiC composite films. Particularly, Sample C250, featuring a carbon content of 35.02 at.%, exhibits higher hardness, elastic modulus, excellent wear resistance, and superior corrosion resistance. However, a further increase in carbon target sputtering power leads to escalated surface roughness and microchannels, ultimately resulting in reduced wear and corrosion performance. Electrochemical analysis reveal that the strong synergistic effect of amorphous carbon as well as the metal oxide phase formed on the surface significantly enhanced the corrosion resistance of the film in artificial seawater with a corrosion current density as low as 1.8 × 10−8 A/cm2.

TiC nano-coating and their tribological properties were deposited by doal-ion beam sputtering on the tool surface

By using the method of doal-ion beam sputtering deposition, N element is injected with ions to assist sputtering deposition of TiC to prepare the TiC nano-coating with high binding strength. SEM, XRD, dynamic ultra-micro hardness tester, friction and wear testing machine were used to characterize and analyze TiC properties. The results show that the TiC coating prepared by double ion beam sputtering deposition has high hardness, high bonding strength, good friction and wear performance, and improves tool service life.

Carbides formation in weld metal produced by recycling of titanium machining swarf

Application of titanium alloys for orthodontic implants have increase in last years and it has generated a great amount of titanium chips which are disposed as metal scrap. Titanium carbide has high hardness and can be applied as coating reinforcement against wear. Chips of titanium alloys were processed and used in the fabrication of experimental hardfacing consumables for improving the resistance of wear of mechanical components. Coatings were produced in cast steel specimens using the gas tungsten arc welding process. Microstructure was investigated by means of scanning electron microscopy. Microhardness of the coatings was analyzed by a dynamic ultra-micro hardness tester. The microstructure of the welding metal was composed of circular particles of titanium carbide surrounded by a ferritic matrix. The measures made by electron dispersive spectroscopy showed a variation in titanium amount trough the weld, where larger contents of titanium were found, and the matrix. The crystallographic analyses reinforced the formation of titanium carbides embedded in a ferrite matrix into welding metal.

Structures and properties of Ti-5Al-5Mo-5V-1Cr-1Fe after Nb implantation

In this study, Ti-5Al-5Mo-5V-1Cr-1Fe was implanted with Nb at 45 kV with dosages ranging from 1.0 × 1016 ions/cm2 to 1.0 × 1017 ions/cm2 in order to investigate their influence on the wear resistance and fatigue performance. The microstructure and elemental depth profiles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The roughness and mechanical behavior were studied using the optical 3D Infinite Focus and dynamic ultra-microhardness tester respectively. Experimental results indicated that the wear resistance against a GCr15 ball was improved after Nb implantation. Particularly, the specific wear rate of the implanted samples with a dosage of 5.0 × 1016 ions/cm2 was lowest (0.2 mm3·N−1·m−1), nearly 10% of the substrate. However, the theoretical fatigue limit of the substrate decreased after Nb implantation. The mechanisms on how wear and high-cycle fatigue properties were affected by Nb implantation with different dosages were discussed in detail.

Investigation of the Mechanical Properties of Acrylonitrile Butadiene Styrene (ABS)-Nanosilica Reinforced Nanocomposites for Fused Filament Fabrication 3D Printing

To expand the capabilities of 3D printed structures generated from commercial thermoplastic printers, this paper presents the fabrication of polymer filaments that contain inorganic nanoparticles. Nanosilica was dispersed ultrasonically into acrylonitrile butadiene styrene (ABS) and extruded into filaments for fused filament fabrication (FFF) 3D printing. The produced filaments had nanosilica compositions of 5% and 10%wt. A dynamic ultra-micro hardness tester was used in order to characterize the mechanical behavior of the filaments. Also, 3D printed tensile specimens were used to obtain the strain-strain curves and monitor the tensile strength of such structures. The morphology of the nanosilica/ABS composite was studied with a scanning electron microscope (SEM). The results from the dynamic ultra-micro hardness tester reveal that the incorporation of nanosilica particles increases the stiffness and hardness of the ABS material especially in the case of 10%wt concentration. However, for such concentration 3D printing was not possible due to the severe embrittlement of the material. 3D printed structures produced in the form of tensile specimens from the 5%wt nanocomposites display a higher breaking point stress and stiffness than those printed from the pure ABS polymer.

Evaluation of degree of conversion, microtensile bond strength and mechanical properties of three etch-and-rinse dental adhesives

Abstract This study evaluated microtensile bond strength (µTBS), degree of conversion, modulus of elasticity and ultramicrohardness of three etch-and-rinse adhesives systems. The materials evaluated were: Ambar (FGM), Optibond (Kerr) and Magic Bond (Vigodent). The degree of conversion was analyzed by FTIR/ATR. To evaluate bond strength (μTBS) in dentin, 15 teeth (n = 5) were restored and sliced to obtain the specimens (0.8mm2). The dynamic ultra microhardness tester was used to evaluate the hardness and modulus of elasticity. The Magic Bond adhesive system showed lower µTBS than Ambar and Optibond (p <0.001). For degree of conversion, comparisons between groups of adhesive systems evaluated showed statistically significant difference (p<0.001), with higher values for Ambar and Optibond when compared a Magic Bond. For modulus of elasticity and ultramicrohardness, Ambar and Magic Bond showed lower values than Optibond. The best results in all properties evaluated were obtained by the Optibond adhesive system.

Influence of carbon nanotubes functionalization on the mechanical properties of polymethacrylate nanocomposites

Nanocomposites based on poly (methyl methacrylate) (PMMA) and a copolymer of methyl methacrylate and hexyl methacrylate were investigated. The fillers were: multi walled carbon nanotubes (MWCNTs) and functionalized MWCNTs (oxidized). The samples were studied by the depth sensing indentation methods (DSI) based on measurement of load–displacement curves at a constant loading speed. The tests were performed on a dynamic ultra microhardness tester DUH-211S in accordance with ISO 14577-1. The dynamic hardness, Martens hardness, indentation hardness, indentation modulus and elastic part of the deformation work were measured. Classical Vickers hardness was also determined.It was established that the mechanical properties of the polymer matrices have been improved by adding 1% of MWCNTs in spite of their being or not functionalized. The presence of functionalized nanotubes had a particular effect upon the different polymer composites. They improved the micromechanical characteristic for PMMA composites and worsened those of copolymer composites. The following assumptions about the structural peculiarities of the composites investigated have been proposed: the reason for the different effect of the modified carbon nanotubes are the length of the side chains and different interaction; the long hexyl groups spatially hinder the contact of the ester groups with functionalized MWCNTs and thus facilitate the agglomeration of the latter.

Effect of Fluoride-Releasing Adhesive Systems on the Mechanical Properties of Eroded Dentin.

The aim of the study was to evaluate the effect of erosive pH cycling with solutions that simulate dental erosion on Martens hardness (HMV) and elastic modulus (Eit) of dentin restored with fluoride-releasing adhesive systems. Twenty-seven bovine dentin slabs were restored with three adhesive systems: Adper Single Bond 2 total-etch adhesive system, One Up Bond F and Clearfil SE Protect fluoride-containing self-etching adhesive systems. The restorations were made with Filtek Z250. The HMV and Eit values at distances of 10, 30, 50 and 70 µm from the interface were evaluated using a dynamic ultra microhardness tester before and after immersion in deionized water, citric acid and hydrochloric acid (n=9). Data were submitted to repeated-measures ANOVA and Fisher's PLSD tests (=0.05). After erosive cycling, HMV values of dentin decreased in all groups. For dentin restored with Adper Single Bond 2, the lowest values were found closer to the hybrid layer, while for One Up Bond F and Clearfil SE Protect, the values remained unaltered at all distances. For dentin restored with fluoride-releasing adhesive systems, a decrease in Eit was found, but after 30 µm this difference was not significant. The acid substances were able to alter HMV and Eit of the underlying dentin. For fluoride-releasing adhesives, the greater the distance from bonded interface, the lower the Eit values. The fluoride in One Up Bond F and Clearfil SE Protect was able to protect the underlying dentin closer to the materials. In this way, the fluoride from adhesive systems could have some positive effect in the early stages of erosive lesions.

Torsional Fretting Wear Behavior of Duplex DLC Coatings Deposited on Ion Nitriding Treated LZ50 Steel

Duplex ion nitriding/DLC coatings were prepared on LZ50 steel. Characterizations were detected by scanning electron microscopy, atomic force microscope, Raman spectroscopy, dynamic ultra-micro hardness tester, and profilometer. The torsional fretting wear behaviors of DLC coatings and substrate LZ50 steel against GCr15 steel ball in dry conditions were studied under angular displacement amplitudes within a range of 0.1°–5°, constant normal load of 50 N, and rotational speed of 0.8° s−1. DLC coatings presented dense structure and high hardness. Compared with the substrate, DLC coatings removed the mix fretting regime and shifted the slip regime to low angular displacement amplitudes. The friction torques of DLC coatings were lower than that of the substrates. In the partial slip regime, the damage of DLC coatings was low. In the slip regime, the damage mechanism combined with delamination, abrasive wear, and graphitization. The DLC coatings exhibited good capability for anti-torsional fretting damage.

Thermal Degradation and Microhardness Analysis of Polyene with Modified Oil Resin

Thermal degradation of polyene synthesized from recycle polyvinyl chloride (PVC) and hardness of polyene coated with modified oil has been studied by thermogravimetric analysis (TGA) and microhardness test. The synthesized polyene from reaction of recycle PVC were varied from 30 minutes, 1 hour, 2 hours and 4 hours and their thermal stability has been analyzed. From differential thermal gravimetric, DTG curve, polyene from two hours reaction showed the highest degradation temperature up to 445°C due to degradation of polyene sequences. Microhardness test performed by Shimadzu DUH 211/DUH-211S dynamic ultra microhardness tester according to ASTM E384 showed that polyene derived from 2 hours PVC with modifed oil resin resulted in the highest microhardness ~ 107.99 MPa.

Influence of Nanostructured Fibers on Properties of Building Composites

Currently, interest in nanotechnology concept for cement composites is steadily growing. Results of investigations of the concrete surface, reinforced with nanostructured mineral fibers by using atomic force microscopy (AFM) and dynamic ultra-micro hardness tester (DUMHT) of the specific areas of surface are presented. For comparison plain concrete and concrete with addition of single mineral fibers investigated as well. The analysis of the obtained data has shown that as a result of the directed microdisperse structurization provided by nanoinitiators on a surface of fibers, increase strength and deformation characteristics of a material. The main objective of this paper is to research the mechanisms of pattern formation surface of the concrete contained the High-modulus basalt microfiber (HMBMF) as a solid carrier for nanoparticles.

Surface nanocrystallization of aluminium alloy by controlled ball impact technique

A novel surface modification process namely controlled ball impact peening was developed for synthesizing a nanostructured surface layer and to impart compressive residual stresses on metallic materials in order to enhance the overall surface properties. This article demonstrates the microstructural evolution, surface hardening and introduction of the residual stresses in the ball impact peened aluminium alloy surfaces, AA6063-T6. Hardened steel balls were impinged in controlled manner inducing high strain rates on the aluminium samples which are precisely moved using independent programmable logic controlled linear actuators in the controlled ball impact peening process. Mechanical properties of the nanocrystalline surface layer were investigated using dynamic ultra micro-hardness tester. The hardness of the nanocrystalline surface layer is (~1.3GPa) improved compared to the matrix (~0.58GPa) and the depth of the hardened layer is about ~350μm depending upon the peening conditions. The amount of compressive residual stress developed by the treatment is also studied using depth sensing indentation method. The surface compressive residual stresses induced in the ball impact peened samples is about 70–127% of yield strength of the target material depending upon the peening conditions. X-ray diffraction analysis and transmission electron microscope analysis revealed the formation of nanograin crystalline structure on the ball impact peened surface layer. The mean grain size of the peened sample determined by transmission electron microscope is about 8±2nm in the top surface layer. High strain rate and repeated directional loading imparted in the contact zone generates the various dislocation activities and microstructural features which were responsible for the formation of the randomly oriented nanostructured grains on the metallic materials. With increasing strain, the various microstructural features produced in the ball impact peened aluminium samples are deformation twins, multiple shear bands, high density dislocation and dislocation pile-up at the grain boundaries as investigated by transmission electron microscope. Grain refinement on the ball impact peened aluminium surfaces resulted in the formation of high density dislocation associated with the subdivision of original grains into subgrains. The peening coverage and number of overlapping impacts depend upon the sample travelling velocity, which in turn affects the hardness, compressive residual stresses induced and grain size formed for a given ball diameter and impact velocity.

Heat Treatment Effects on Mechanical Properties of Atmospheric Plasma Sprayed FexB Coatings on Al Substrate

In this work, we draw attention to determination of heat-treatment effects on mechanical properties of atmospheric plasma sprayed (APS) FexB coatings on aluminum substrates by micro-indentation technique. With this regard, iron boride powders of Fe-18.8B-0.2C-0.5Si-0.8Al (wt.%) were deposited onto Al substrates by APS in order to improve the mechanical properties of Al surface. As-sprayed coatings are composed of mainly FexB and iron matrix supersaturated with boron owing to the rapid solidification of molten droplets flattened on a substrate. It was observed that APS coatings exhibited characteristic wavy layered structure having porosity, inclusions, and semi-melted particles. The postfurnace treatment of APS coatings was carried out at temperatures ranged from 450 to 550°C in an argon atmosphere. The post-treatment applied for APS deposits led to increase in hardness of 40% without showing cracks. Furthermore, micro-mechanical properties of FexB coatings were examined by Shimadzu Dynamic Ultra-Microhardness Tester for estimating Young’s modulus and hardness due to load—unload sensing analysis by applying different loads such as 160, 320, and 640 mN to determine load and indentation depth dependency of APS FexB on Al substrate for each samples, in details.

An investigation into the mechanical and tribological properties of plasma electrolytic oxidation and hard-anodized coatings on 6082 aluminum alloy

Abstract A ceramic coating on AA6082 aluminum alloy prepared by plasma electrolytic oxidation (PEO) has been studied and compared against a sulphuric acid hard-anodized coating on the same alloy. Surface morphology and microstructures of the coatings have been examined by scanning electron microscopy. X-ray diffraction is used to determine the phase composition of the coatings. The adhesion strength of the coatings has been evaluated using a scratch test method. The coating's mechanical properties such elastic modulus and hardness data have been generated using a dynamic ultra-microhardness tester. Sliding wear tests with different loading rates are performed on the coatings in order to assess their wear resistance. Test results show that the PEO treated samples exhibit significantly better mechanical properties compared to hard anodized samples. The elastic modulus and hardness of the PEO coating are 2–3 times greater than of the hard anodized coating and subsequently, an improved wear resistance of the PEO coating has been achieved. The mechanical properties of the coatings and their relations to their tribological performance are discussed.

Co-deposited Zn-submicron sized Al 2O 3 composite coatings: Production, characterization and micromechanical properties

In this study, co-deposition of zinc (Zn)-submicron sized alumina (Al 2O 3) particles via electrodeposition method was investigated. Composite coatings were produced using different coating parameters such as current density, pH, temperature, agitation type, and ceramic powder content of the bath solution. Structural and microstructural properties of the coatings were characterized by X-ray diffractometer (XRD) and scanning electron microscopy with electron dispersive spectroscopy (SEM–EDS). Mechanical properties of the coatings were evaluated by dynamic ultra-micro hardness (DUH) tester, a micro-indentation technique, in detail. It was found that, co-deposition of submicron sized Al 2O 3 particles and Zn metal was successfully achieved via electrodeposition method without any chemical interaction between the ceramic particles and the electrolyte. Comparison of SEM images belonging to the coatings fabricated to those of the reference coatings revealed that homogenous grain structure was obtained. Finally, a boost in the micromechanical properties of the coatings was gained by changing the effective co-deposition parameters such as current density and particle content in the electrolyte.

Indentation creep of composite resins

Creep behavior of restorative materials is an important mechanical property. Indentation creep of 6 different composites was evaluated at ageing times of 15 min and 1 week using a Dynamic Ultra-Microhardness Tester. The influence of water on indentation creep was slso assessed. The results were as follows: 1. All the composites showed creep and the amount of creep was different among the composites at 15min. and 1 week. 2. Water absorption increased creep. 3. All the materials showed a decrease in creep with time when stored in air. 4. Under scanning probe microscopy, the ridges of the diamond triangular pyramid indenter were sharp and the three sides of indentation were bow-shaped toward the center of indentation.

Multiscale analysis of stress distribution in teeth under applied forces

Objectives The present study aimed to clarify stress distribution in teeth under an external applied load using microindentation and multiscale simulation. Methods Anisotropic material properties of enamel and dentin were measured using a microindentation method with a dynamic ultra microhardness tester. The numerical model was constructed using the finite element mesh superposition method with a microscale (enamel rods), mesoscale (teeth), and macroscale (bone). Multiscale simulation was used to analyze different scale structures. A concentrated load (10 N) was applied to the labial surface of the central incisor. Results The results revealed stresses of 5 MPa (normal stress) and 6.5 MPa (shear stress) in the enamel sheath at the center of the labial region compared to 1.4 MPa (normal stress) and 21.4 MPa (shear stress) in the cervical region. Significance These results suggest that shear stresses in the enamel sheath may play significant roles in stress transmission.

Preparation and property characterization of PAA/Fe3O4 nanocomposite

PAA/Fe3O4 nanocomposites were prepared by mixing nano-Fe3O4 and polyacrylic acid (PAA) ethanol solution and then evaporating the solvent. The materials were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscope (FTIR), thermogravimetry analysis (TGA), dynamic ultra-micro hardness tester (DUMHT) and superconducting quantum interference device (SQUID) magnetometer. Results showed that PAA coordinated with nano-Fe3O4 to form a cross-linking structure. The presence of nano-Fe3O4 enhanced the thermal stability of the nanocomposite. The elasticity and hardness of the nanocomposite increased, and the indentation depth reduced with the increase of Fe3O4 content in the composites. The nanocomposites showed superparamagnetic properties at 300 K.

Structural Characteristics of the Modern Sintered Tool Materials

Within the project framework the structure and properties was investigated of the cemented carbides, cermets and oxide ceramics using the scanning electron microscope (SEM). The X-ray qualitative microanalysis and surface distribution analysis of elements in the investigated materials were made using the EDS X-ray energy dispersive radiation spectrometer. The roughness measurements of the developed materials were made in two orthogonal directions. The Ra parameter was assumed to be the value describing surface roughness. The microhardness tests using the Vickers method were made on the dynamic ultra microhardness tester. The measurements were made in the „load - unload” mode.