Changes In Hardness Research Articles

Surface modification of fly ash by waste engine oil under mechanical activation enhanced the sustainable service life of asphalt

Oxidative aging of asphalt leads to changes in its molecular structure and chemical composition, deteriorating the properties. Therefore, extending the service life of asphalt materials is essential for environmental protection and sustainable development. In this study, waste engine oil (WEO) with similar components and chemical composition to asphalt was used to modify the fly ash (FA) surface by a high-energy ball grinding process to produce a well-compatible compound fly ash modifier (CFAM). This process achieved ultra-refinement and surface modification in one step, enhancing the chemical bonding and anchoring force between FA and asphalt, thereby effecting the ageing resistance of the asphalt. Dynamic light scattering tests showed that the oil grinding process enhanced the stability of CFAM, whose median particle size (654 nm) increased by only 103 nm after four months of storage. Thermogravimetric (TG), BET tests showed that the FA surface was grafted with a large amount of WEO, and the CFAM after de-oiling and rinsing had a WEO content of 1.39 wt%, which gave it excellent compatibility with asphalt. The nano-indentation and Fourier transform infrared spectroscopy (FTIR) experiments showed that CFAM reduced the changes in micro hardness, modulus of elasticity, carbonyl content and sulfoxide group content of asphalt before and after ageing and provided an excellent anti-ageing effect. The oil grinding process activated the reactivity of the FA that could chemically bond with the carboxylic acids in the asphalt, stabilizing the chemical components of the asphalt and delaying the ageing of the asphalt, thus achieving sustainable service of the asphalt.

Experimental research of the explosive welding of metal plates with different initial hardness

ABSTRACTThe results of studies of explosively welded NiCr-alloy (Cr20Ni80) + titanium alloy (OT4/VT20) composites are presented. The main parameters of explosive welding have been calculated. The wavy profile parameters and peel strength of composites after explosive welding in various modes was determined. It is shown that the change in the structure and properties of the welded joint is due to both the change in the initial hardness of the titanium alloy and the change in the collision point velocity. It was established that the molten metal are heterogeneous mixtures based on Ni(Cr,Ti) and Ti(Ni,Al) solid solutions and NiTi and Ni3Ti intermetallics. FEM modeling was carried out to determine the lifetime of the molten metal in the liquid state during the welding process. The calculated values of the molten metal cooling rates are 107–1010 K/s. Due to these values both stable crystalline and unstable (amorphous) phases are formed.

Magnolol Loaded on Carboxymethyl Chitosan Particles Improved the Antimicrobial Resistance and Storability of Kiwifruits.

Magnolol is a natural compound extracted from the traditional Chinese medicine Magnolia officinalis, which exhibits antimicrobial properties. However, magnolol is insoluble in water and consists of a phenolic hydroxyl group, which is volatile; these factors hinder its application. In this study, a safe and environmentally friendly method to improve the microbial resistance and storability of harvested fruits is developed using the water-soluble carrier carboxymethyl chitosan (CMCS) and magnolol. Magnolol was loaded on CMCS particles to form Magnolol@CMCS antimicrobial particles, a preservation coating agent. Magnolol@CMCS particles effectively solved the problems of water insolubility and agglomeration of magnolol and reduced the size distribution D50 value of magnolol from 0.749 to 0.213 μm. Magnolol@CMCS particles showed greater toxicity against Staphylococcus aureus, Escherichia coli, and Botryosphaeria dothidea than that of magnolol alone, with effective medium concentration (EC50) values of 0.9408, 142.4144, and 8.8028 μg/mL, respectively. Kiwifruit treated with the Magnolol@CMCS solution showed delayed changes in fruit hardness and soluble solid and dry matter contents and significantly higher ascorbic acid (vitamin C) and soluble total sugar contents and sugar:acid ratios compared with that of the control fruit. In addition, no disease spots were observed on fruit treated with the Magnolol@CMCS solution within 7 days after inoculation with B. dothidea. In conclusion, Magnolol@CMCS particles showed antimicrobial activity on harvested fruits, effectively delayed the hardness and nutritional changes of fruits during storage, and improved the storability of kiwifruit.

Moisture Content and Mechanical Properties of Bio-Waste Pellets for Fuel and/or Water Remediation Applications

The current research is focused on the mutual comparison (mechanical properties, response to humidity) of agro-waste composite materials. The purpose of this work is directed at the valorization of agro-waste biomass products and to investigate their mechanical stability for transport or other applications (in dry and wet states). Three different types of agro-waste (oat hull (Oh), torrefied wheat straw (S), and spent coffee grounds (SCG)) were blended with kaolinite (K) and chitosan (CHT) at variable weight ratios to yield ternary composites. Mechanical properties were represented by measuring hardness (in compression mode) and elastic modulus (under tension mode). Young’s (elastic) modulus was measured both for dried and hydrated samples. The pelletized materials were prepared in two forms: crosslinked (CL) with epichlorohydrin and non-crosslinked (NCL). The hardness of the Oh pellets was poor (75 N) and decreased by four times with greater agro-waste content, while crosslinking affected the hardness only slightly. S pellets had the highest level of hardness at 40% agro-waste content (160 N), with a concomitant decrease to 120 N upon crosslinking. SCG pellets had the least change in hardness for both CL and NCL specimens (105–120 N). The trends of Young’s modulus were similar to hardness. Hydration caused the elastic modulus to decrease ca. 100-fold. In general, S and SCG composites exhibit the greatest hardness and Young’s modulus compared to Oh composites (CL or NCL) in their dry state.

Immediate implant placement with flap or flapless surgery: A systematic review and meta-analysis.

To assess the impact of mucoperiosteal flap elevation for single immediate implant placement (IIP) on buccal hard and soft tissue changes, and on clinical, aesthetic and patient-reported outcomes. Two independent reviewers conducted an electronic literature search in Pubmed, Web of Science, Embase and Cochrane databases as well as a manual search to identify eligible clinical studies up to June 2022. Randomized controlled trials (RCTs) comparing IIP without flap elevation to IIP with flap elevation were included for a qualitative and quantitative analysis. The primary outcome was horizontal buccal bone change. Secondary outcomes were implant survival, vertical buccal bone change, pain, and clinical and aesthetic parameters. Out of 1029 records, 5 RCTs were selected reporting on 140 patients who received 140 single immediate implants (flapless: 68; flap: 72). Patients had a mean age ranging from 30 to 67 years and were followed between 6 and 12 months. Four RCTs pertained to (nearly) intact alveoli. Risk of bias assessment yielded low risk for two RCTs and high risk for three RCTs. Meta-analysis demonstrated a mean difference of 0.48 mm (95% confidence interval [CI] [0.13, 0.84], p= .007) in horizontal buccal bone change between surgical approaches, favouring flapless surgery. Meta-analysis failed to demonstrate a significant difference in implant survival between the groups (RR 1.00, 95% CI [0.93, 1.07], p= .920). Given the scarcity of data, meta-analyses could not be performed on other secondary outcomes. Available studies were consistent in the direction of the effect favouring flapless surgery for vertical buccal bone change as well as for pain. Clinical and aesthetic parameters were underreported. Based on CBCT data, flapless surgery resulted in more buccal bone preservation at immediate implants. However, the clinical relevance of this finding is unclear, since clinical and aesthetic outcomes were underreported.

Geochemical extraction of ceratopsian remains from ironstone

ABSTRACT Ironstone surrounds many fossils and has a hardness that provides a significant challenge to fossil conservators globally. There are various forms of ironstone, with the carbonate forms of siderite and silicates most often containing vertebrate fossils and potentially preserved soft tissues. The ironstone itself is much harder than the fossils preserved within, leading to the mechanical preparation of the fossils––typically using pin vises or airscribes––being time-consuming and presenting the risk of damage. Existing chemical methods for softening ironstone to prepare the fossils have varied success and also pose a risk of damaging the fossil itself. Here we show that carbonic acid can soften ironstone without damaging permineralized bone or potentially preserved soft tissues. Carbonic acid treatments reduced the hardness of ironstone without causing any significant change in hardness, color, chemical composition, or weight to permineralized ceratopsian bones or a modern cervid bone that retained nonmineralized internal tissues. In addition, we found that solutions of sodium hydroxide and hydrogen peroxide were viable for softening ironstone to remove from the permineralized bone when preserved soft tissue recovery is not a priority. The treatments proposed in this study are important as they are applicable to a range of preparation scenarios, are cost-efficient, are relatively safe to handle, and cause no damage to permineralized fossil bones. Putting these methods into practice can lead to more efficient and safe preparation of fossils in ironstone.

Effect of Tempering Temperature on the Microstructure and Mechanical Properties of 42CrMo4 Steel

This paper investigated the effects of tempering temperature (200°C, 400°C, 600°C or 800°C) on microstructures, mechanical properties, and residual stress of 42CrMo4 steel. Microstructures were characterized by OM and SEM techniques. The results show that the change in tempering temperature leads to a change in austenite, resulting in a change in hardness and toughness. The specimen showed the best combination of mechanical properties under the heat treatment condition of a tempering temperature of 600°C. The hardness, yield strength, tensile strength, area shrinkage, and elongation reached 312.74HV, 759MPa, 898MPa, 60%, and 18%, respectively. The experimental results provide a reference for the selection of the heat treatment process of 42CrMo4 steel.

Management of Root Sensitivity following Socket Shield Technique with Anterior Single Immediate Implant Placement and Provisionalization.

Maintaining facial soft tissue contour and inter-implant papilla are challenging for implants in the esthetic zone. To counteract the inevitable hard and soft tissue changes after tooth extraction, the socket shield technique (SST) has been advocated as means to maintain the facial and/or interproximal osseous and gingival architecture. Because SST is a technique-sensitive procedure, various complications related to SST have been reported. This article presents a unique complication after a socket shield procedure and a novel management of the complication. Int J Periodontics Restorative Dent 2023;43:157-165. doi: 10.11607/prd.5426.

Influence of functional groups in chemical reactivity and optoelectronic properties of novel glycidyl nitrate copolymers (GNCOP): a DFT study.

Nowadays, propulsion materials are receiving increased attention as an important component in electric motors. So, awareness of their chemical reactivity and geometric and electronic structures can help to make materials with higher quality and efficiency. In this study, we have proposed novel glycidyl nitrate copolymers (GNCOPs) and meta-substituted derivatives as propulsion materials. Based on density functional theory (DFT) method, chemical reactivity indices have been calculated for predicting their behavior in burning process. Adding functional groups changes reactivity of the GNCOP compound, especially, in the -CN functional group, chemical potential, chemical hardness, and electrophilicity change -0.374, +0.007, and +1.342eV, respectively. In addition, these compounds have dual properties in interaction with oxygen molecule. Optoelectronic study in time-dependent DFT framework shows that there are three peaks with significant excitations. In conclusion, adding functional group into the GNCOPs can introduce new materials with high energetic properties.

Food Hardness Modulates Behavior, Cognition, and Brain Activation: A Systematic Review of Animal and Human Studies.

Food hardness is one of the dietary features that may impact brain functions. We performed a systematic review to evaluate the effect of food hardness (hard food versus soft food diet) on behavior, cognition, and brain activation in animals and humans (PROSPERO ID: CRD42021254204). The search was conducted on 29 June 2022 using Medline (Ovid), Embase, and Web of Science databases. Data were extracted, tabulated by food hardness as an intervention, and summarized by qualitative synthesis. The SYRCLE and JBI tools were used to assess the risk of bias (RoB) of individual studies. Of the 5427 studies identified, 18 animal studies and 6 human studies met the inclusion criteria and were included. The RoB assessment indicated that 61% of animal studies had unclear risks, 11% had moderate risks, and 28% had low risks. All human studies were deemed to have a low risk of bias. The majority (48%) of the animal studies showed that a hard food diet improved behavioral task performance compared to soft food diets (8%). However, 44% of studies also showed no differential effects of food hardness on behavioral tests. It was also evident that certain regions of the brain were activated in response to changes in food hardness in humans, with a positive association between chewing hard food, cognition performance, and brain function. However, variations in the methodologies of the included studies hindered the meta-analysis execution. In conclusion, our findings highlight the beneficial effects of dietary food hardness on behavior, cognition, and brain function in both animals and humans, however, this effect may depend on several factors that require further understanding of the causality.

Three-dimensional volumetric assessment of hard tissue alterations following horizontal guided bone regeneration using a split-thickness flap design: A case series

ObjectivesTo analyze morphological, volumetric, and linear hard tissue changes following horizontal ridge augmentation using a three-dimensional radiographic method.MethodsAs part of a larger ongoing prospective study, 10 lower lateral surgical sites were selected for evaluation. Horizontal ridge deficiencies were treated with guided bone regeneration (GBR) using a split-thickness flap design and a resorbable collagen barrier membrane. Following the segmentation of baseline and 6-month follow-up cone-beam computed tomography scans, volumetric, linear, and morphological hard tissue changes and the efficacy of the augmentation were assessed (expressed by the volume-to-surface ratio).ResultsVolumetric hard tissue gain averaged 605.32 ± 380.68 mm3. An average of 238.48 ± 127.82 mm3 hard tissue loss was also detected at the lingual aspect of the surgical area. Horizontal hard tissue gain averaged 3.00 ± 1.45 mm. Midcrestal vertical hard tissue loss averaged 1.18 ± 0.81 mm. The volume-to-surface ratio averaged 1.19 ± 0.52 mm3/mm2. The three-dimensional analysis showed slight lingual or crestal hard tissue resorption in all cases. In certain instances, the greatest extent of hard tissue gain was observed 2–3 mm apical to the initial level of the marginal crest.ConclusionsWith the applied method, previously unreported aspects of hard tissue changes following horizontal GBR could be examined. Midcrestal bone resorption was demonstrated, most likely caused by increased osteoclast activity following the elevation of the periosteum. The volume-to-surface ratio expressed the efficacy of the procedure independent of the size of the surgical area.

Property-Graded Stainless Steel 316L by Selective Laser Melting: Characterization & Design

Abstract The purpose of this research work is to characterize and inform the design of (mechanical) property-graded bulk structures made from a single metallic alloy via a laser powder bed fusion (LPBF) process, with an end goal of creating repeatable/reproducible functionally-graded additively manufactured (FGAM) parts. This paper specifically investigates the manufacture of stainless steel (SS) 316L structures via a pulsed selective laser melting (SLM) process, and the underlying causes of property variations (within a functionally-acceptable range) through various material characterization techniques. For this, a design of experiments spanning the volumetric energy density (VED) based process parameter design space was utilized to investigate the range of functionally-acceptable physical/mechanical properties achievable in SS 316L. Five sample conditions (made via different process parameter combinations) were down-selected for in-depth microstructure analysis and mechanical/physical property characterization; these were suitably selected to impart a wide and controllable property range (209–318 HV hardness, 90–99.9% relative density, and 154–211 GPa modulus). It was observed that property variations resulted from combinations of porosity types/amounts, martensitic phase fractions, and grain sizes. Based on these findings, property-graded standard test specimens were designed and manufactured for further investigation—tensile specimens having a monotonic hardness change along its gauge length, four-point bending specimens with varying elastic moduli as a function of the distance from the neutral axis, and Moore’s rotating beam fatigue specimens with moduli variations based on the distance from the center. Altogether, this work lays the foundation for understanding and designing the local and global mechanical performance of FGAM bulk structures.

Fabrication of porous pure magnesium by MgH<sub>2</sub> produced by mechanical milling and spark plasma sintering (MM-SPS) process

Pure magnesium (Mg) powders with stearic acid added as process control agent (PCA) were mechanically milled (MMed) using a vibration ball mill. The MMed powders were consolidated into bulk materials by the spark plasma sintering (SPS). Changes in hardness, thickness and solid-state reactions of the SPS materials have been examined by hardness measurements, vernier caliper and an X-ray diffraction (XRD), respectively. The Vickers hardness of the SPS material decreased with increasing sintering temperature. Minimum value of Vickers hardness was 17 HV. The thickness of the SPS material increased with increasing sintering temperature. However, little effect of sintering time on the thickness was observed. In the SPS materials, the formation of MgH2 by solid phase reaction was observed during sintering. During sintering, MgH2 was decomposed to produce hydrogen gas; and it contributed to expand the SPS materials. Porous pure magnesium could be formed using only the MM-SPS process without the addition of a foaming aid.

In situ nanomechanical characterization of hydrogen effects on nickel-based alloy 725 under different metallurgical conditions

• In-situ nanoindentation test was used to study the H effect on alloy 725 • Both solution-annealed and precipitation-hardened alloy 725 were tested • H effect on surface integrity and nanomechanical properties were studied in detail • Different H behaviors were compared based on H content and microstructure The effect of hydrogen on the surface morphology and nanomechanical properties of Ni-based Alloy 725 under solution-annealed (SA) and precipitation-hardened (API) conditions was thoroughly studied. The investigation involved in situ nanoindentation testing, microscopy characterization, statistical analysis, and numerical simulation approaches. The results showed the distinctive effects of hydrogen on the pop-in and hardness in the SA and API samples. For the SA sample, hydrogen mainly dissolved as solid solute in the matrix, causing enhanced lattice friction on the dislocation motion and increasing the internal stress via lattice expansion. Thus, an enhanced hardness, a reduced pop-in width/load ratio, and numerous surface steps were detected in the presence of hydrogen. For the API sample, the strengthening γ’’ phases were the stress concentrators, and the dislocations nucleated heterogeneously, demonstrating indistinctive pop-in phenomena. Furthermore, the precipitates in the API sample affected the trapping behavior of hydrogen, thereby resulting in the hardness change, which reflected the competition between solution hardening in the matrix and vacancy softening mechanism in precipitates.

Effect of low-temperature degradation treatment on hardness, color, and translucency of single layers of multilayered zirconia

Statement of problemEvaluating the effect of low-temperature degradation (LTD) on multilayered zirconia blocks is important for the long-term life of zirconia restorations. PurposeThe purpose of this in vitro study was to analyze the changes in color, translucency, and hardness of a single layer of multilayered zirconia after an LTD treatment. Material and methodsNinety multilayered 10×10×1.0-mm zirconia specimens (3M Lava Esthetic) were designed using Auto CAD 2006 (Autodesk) and divided into 6 groups (n=15) based on LTD (no treatment, LTD treatment) and the inherent layer type (incisal, transition, and body). The hardness of each specimen was measured using a microVickers hardness tester. The CIELab color coordinates were measured using a spectrophotometer, and the data were used to calculate the color difference and translucency (TP). Data were analyzed using 2-way ANOVA and the Scheffé test (α=.05). ResultsLTD treatment did not alter the hardness of multilayered zirconia (P=.572). A significant difference was found in the hardness between the layers of multilayered zirconia (P<.001). LTD treatment did not alter the b∗ or L∗ values (P=.773, P=.701) but did change the a∗ values (P<.001). On LTD treatment, the a∗ value was found to decrease. The L∗, a∗, and b∗ values differed based on the respective layer within the material (P<.001). As layers progress from the incisal to the body, the L∗ value decreased and the a∗ and b∗ values increased. In all groups, the color difference values were highest in the following order: the incisal and transition layers < the transition and body layers < the incisal and body layers. On LTD treatment, the color difference between the layers decreased. The LTD treatment did not affect the TP value (P=.208), but the TP value for each layer showed a significant difference (P<.001). ConclusionsLTD treatment did not affect the optical properties or hardness of the multilayered zirconia. The hardness of the multilayered zirconia increased from the incisal to the body layer. In multilayered zirconia, the brightness decreased from the incisal to the body layer, and red and yellow color changes were observed. The TP of multilayered zirconia increased from the incisal to the body layer.

Elevated-temperature wear behavior of Ti6Al4V alloy: microstructural evolution and properties change in subsurfaces and mild-severe wear transition

Dry sliding wear behavior of Ti6Al4V alloy was studied at elevated temperatures of 50 °C–400 °C. The constituent phases and morphologies of worn surfaces were examined to evaluate the roles of oxide layers and wear mechanisms in mild-severe wear transition (M-SWT). Microstructural evolution and hardness change in subsurfaces were also investigated to reveal the most fundamental reason for M-SWT. The results showed that M-SWT happened via severe plastic deformation (SPD) within 20 °C–350 °C, while mild wear prevailed via a protective mechanically mixed layer (MML) containing multiple oxide phases at 400 °C. Large surface plastic deformation and frictional heat activated dynamic recrystallization (DRX) softening in subsurface, which resulted in M-SWT. The critical load for M-SWT presented an approximate linear relationship with testing temperature within 20 °C–250 °C, from which a critical temperature of 555.8 °C for M-SWT was obtained by linearly fitting method. It was thought as the critical temperature for DRX realization in surface layer, and it was utilized to calculate the transition loads at 300 °C and 350 °C.

Development Optimization and Evaluation of Fast Disintegrating Tablets of Antiepileptic Drug Carbamazepine

Background: The main objective of present research work is to formulate the Carbamazepine as Fast Disintegrating tablets to give fast relief and an increase in the patient compliance. Carbamazepine, an antiepileptic, belongs to BCS Class-II and used to control some types of seizures in the treatment of epilepsy and Neuropathic Pain by blocking use-dependent sodium channels.&#x0D; Methods: The powdered materials were compressed by direct compression technique using super disintegrants like sodium starch glycollate, croscarmellose sodium and starch, Magnesium Stearate and Di Calcium Phosphate are used as lubricant and diluents/fillers respectively.&#x0D; Result and Discussion: Totally nine formulations were designed and are evaluated for hardness, friability, thickness, assay, wetting time, Disintegration time, in-vitro drug release. From the Results concluded that all the formulation were found to be with in the Pharmacopeial limits and the In-vitro dissolution profiles of all formulations were fitted in to different Kinetic models, the statistical parameters like intercept (a), slope (b) &amp; regression coefficient (r) were calculated. The optimized formulation was characterized with the help of Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared Spectroscopy (FTIR) studies show no interaction between the drug and the excipients. The stability study was conducted as per the ICH guidelines and the formulations were found to be stable, with insignificant changes in hardness, drug content and disintegration time.&#x0D; Conclusion: These results revealed that fast disintegrating tablets of the poorly soluble drug, carbamazepine, showing enhanced dissolution and, hence, better patient compliance.

Evaluation of Changes in Soft and Hard Tissues of TMJ among Class II Division 2 Patients after Prefunctional Orthodontics and Twin Block Functional Appliance Therapy: A Prospective MRI Study.

No study has been conducted to explore soft and hard tissue changes brought by functional appliances within the temporomandibular joint (TMJ) after correction of class II division 2 (div 2) malocclusion. Hence, we planned this study to evaluate the mandibular condyle disk-fossa relationship before and after prefunctional and twin block therapy using a magnetic resonance imaging (MRI) scan. This prospective observational study was conducted among 14 males treated with prefunctional appliances for 3-6 months, followed by 6-9 months of fixed mechanotherapy. MRI scan was evaluated for changes in the TMJ at baseline after completion of prefunctional phase and after completion of functional appliance therapy. At pretreatment, there was a flat contour on the posterosuperior surface of the condyles and a notch-like projection on its anterior surface. After functional appliance therapy, slight convexity appeared on the posterosuperior surface of the condyle and the prominence of the notch was reduced. There was a statistically significant anterior shift of condyles both after prefunctional and twin block treatment. The meniscus on both sides had significantly shifted posteriorly over three stages with respect to the posterior condylar (PC) plane and Frankfort horizontal (FH) plane. The superior joint space had significantly increased with significant linear glenoid fossa displacement between pre and posttreatment stages. Prefunctional orthodontics induced favorable changes in TMJ soft and hard tissues of patients, but they were not sufficient to place the soft and hard tissues in their normal positions. A functional appliance phase is needed to place the TMJ in their respective normal positions. Patel B, Kukreja MK, Gupta A, et al. Evaluation of Changes in Soft and Hard Tissues of TMJ among Class II Division 2 Patients after Prefunctional Orthodontics and Twin Block Functional Appliance Therapy: A Prospective MRI Study. Int J Clin Pediatr Dent 2022;15(5):479-488.

Martens hardness of Constantan thin films on (100) Si wafer: Improvement in contact area function in nanoindentation

This work presents a mechanical study by nanoindentation of Constantan thin films deposited by cathodic sputtering technique with an intermediate thin adhesion layer of titanium on a (100) silicon wafer substrate. A methodology based on a modified contact area function is proposed for a suitable processing of the nanoindentation data in order to extract the Martens hardness both of the substrate, titanium layer and Constantan films. The raw data of the substrate Martens hardness have been studied using the most useful models among them those of Nix & Gao, Li & Bradt and Bull & Page showing a significant indentation size effect. However, when considering the tip defect length in the Martens hardness computation, the corrected values are found constant and no indentation size effect occurs. Within this objective, an accurate determination of the tip defect length is required. Its value has been determined both with a correlation between the contact area function of Oliver & Pharr and the improved model of Chicot et al. and also with the self-calibration method proposed by Chicot et al. The tip defect length is afterwards implemented in the model of Jönsson & Hogmark modified by Rahmoun et al. for the hardness determination of the titanium layer and the Constantan thin films. As a main result, the Martens hardness of the titanium layer and of the substrate are found equal to 8 GPa thus allowing to neglect the influence of the titanium layer in the film hardness determination. As a main result, the hardness of the 4 Constantan films is constant whereas the substrate hardness changes with the film thickness. This unexpected behavior is related to the brittleness of the substrate where cracks are observed at the interface and by the film compacting which is trapped between the rigid indenter and the hard substrate.

Surface Hardness Modification of Selective Laser Melted Ti6Al4V Parts by Sliding Friction Diamond Burnishing

Selective laser melting (SLM) is a frequently used additive manufacturing technology for creating metallic, especially Ti6Al4V parts. After the production by SLM usually postprocessing is necessary for several reasons. Here the sliding friction diamond burnishing is applied as postprocessing procedure.In this paper an experimental study of surface hardness improvement of selective laser melted Ti6Al4V ELI cylindrical parts is demonstrated. The surface is modified by sliding friction diamond burnishing as postprocessing machining. The design of experiment method was applied to investigate effect of five factors (two SLM and three machining parameters) on surface hardness modification.It is shown that both SLM and postprocessing factors makes significant effect to the surface hardness improvement, most important ones are laser power, laser scan speed during manufacturing, and the burnishing force as factor of postprocessing. Empirical formulas are fit to measurement data, and visualized by surface plots. Relationship between factors and the surface hardness improvement is strongly nonlinear. In the investigated parameter window burnishing force has always positive effect to surface hardness improvement.Electron microscopic investigations show that change in surface hardness can be related to four main morphological changes: compression of the surface by plastic deformation of protrusions, attenuation of valleys, formation of inner cavities and creation of small protrusions by diamond tool. This paper is an extended paper of a conference paper published in the proceedings book of the XXXI. International Welding Conference (Kecskemét, Hungary).