Surface Hardness Values Research Articles

Comparative Evaluation of The Microhardness of Artificial Teeth of Various Composition

Statement of the problem: To help physicians choose the right materials for treatment planning, it is necessary to investigate to the mechanical and physical characteristics of denture teeth made with new technology. Objective: This study aims to investigate the comparative microhardness of artificial teeth with different composition. Materials & Methods: A total of 96 specimens (n=32) were prepared using three different types of artificial teeth (conventional polymethylmethacrylate, , and nanohybrid composite) (Group CA - Conventional PMMA, Group IS - Isosite Group DCL - double cross-linked acrylic). Surface hardness values were determined using a microhardness tester (Shimadzu HMV Corporation, Tokyo, Japan) with a load of 500 g and a dwell time of 15 seconds. Three indentations were obtained for each sample and the Vickers Hardness Number (VHN) was calculated and averaged. One-way analysis of variance (ANOVA) and post-hoc Tukey HSD tests were used for statistical analysis. The statistical significance level of the data was taken as α=0.05. Results: The highest microhardness values were observed in Group IS (53.96 ± 8.5 VHN) and the lowest in Group CA (53.55±9.9 VHN). However, no statistically significant difference was found between the groups (P>0.05). Conclusions: For the durability and function of prosthetic rehabilitations performed by clinicians, the choice of artificial teeth should not be ignored, based on cost and accessibility criteria.

An assessment of the impact of L.Salvadora persica and G.Tea on the surface roughness and hardness of heat-cured acrylic-based denture soft liners.

Background: Soft denture liners are a type of dental prosthesis that functions as a cushioning material, alleviating the stress induced by the act of chewing. They offer relief to persons who encounter discomfort when wearing complete or partial dentures, particularly when these dentures are situated on rigid surfaces that support the denture. The objective of this study: is to assess the effects of including L.Salvadora persica. and green tea (G.Tea) extract powders on the surface roughness and hardness characteristics of acrylic-based soft liners. Materials & Procedures: 30 specimens were constructed using wax molds and acrylic-based heat-cured denture soft lining material. The standard curing procedure was used. The samples were separated into three equal groups: group A, the control group, with no additives in the soft-liner material; group B, with 5.12% weight percept L.salvadora persica extract powder; and group C, with 5.12% weight present green tea (G.Tea) extract powder. The samples were then prepared for surface hardness and roughness testing. Results: The results revealed that there was a non-significant rise in the mean values of surface roughness for both group B and group C, group B having the highest mean values followed by group C. When compared to the control group, the results showed a considerable rise in the mean values of surface hardness in group (B), which had the highest mean value for surface hardness, followed by group (C). Conclusion: The results of this study indicate that the incorporation of L.salvadora persica at a concentration of 1.024g and green tea (G.Tea) extract powders at a concentration of 1.024g shown a positive impact on the surface hardness of denture soft lining materials

Effect of Carburizing Temperature and Post Carburizing Treatments on Microhardness and Microstructural Evolution of Carburized Low-Carbon Steel

This paper reports the results of an experimental investigation of the effect of carburizing temperature and post carburizing heat treatments on the structural and hardness properties of pack carburized low-carbon steel. The carburizing processes were performed at temperatures of 900°C and 1035°C for 6 hours. After that, two hardening procedures were carried out. In the first hardening procedure, the specimens were directly quenched in oil from carburizing temperatures, while in the second procedure, a double quenching method using brine as a quenching medium was applied. The resultant changes in surface hardness values, carbon content, case depth, microhardness profiles, and microstructural evolution during all processes were tracked and reported. The study showed that the hardness values and carbon content of the carburized specimens increased significantly compared to an untreated specimen, also case depth values increased by two times in some hardened specimens, the increasing in these values were correlated to the changes in microstructures. The obtained results indicated that the structure and the properties of the carburized components are strongly influenced by carburizing temperature and by post carburizing heat treatments; therefore, both variables can be used to altering or modifying surface and core characteristics of the carburized steel, which make it more suitable for engineering components that require a combination of hard surface along with ductile and tough core.

ANALISIS SURFACE HARDNESS ALUMINUM 6061 HASIL GAS NITRIDING DENGAN VARIASI HOLDING TIME

The nitriding coating process is widely applied in the industry. Gas nitriding is a technique used to improve the mechanical properties of a metal. This study aims to determine the influence of holding time variations on surface hardness and diffusion depth in aluminum alloy 6061 (Al-Mg-Si) that undergoes gas nitriding. The independent variable used in this study was holding time, namely, initial specimen (without holding time treatment), and specimens that experienced holding ranging from 1 hour, 2 hours, 3 hours, 4 hours, and 5 hours. The cooling medium used after gas nitriding was air. The highest surface hardness value was obtained in aluminum alloy 6061 specimens without holding time treatment, namely with a hardness value of 141 VHN while the lowest surface hardness value was produced by the specimen with a holding time of 5 hours. The lowest surface hardness value was 55.4 VHN. Based on the results of the EDAX composition test known that the specimen of aluminum alloy 6061 with a holding time of 5 hours diffused nitrogen element of 1.57% and oxygen element of 5.27%.

Application of 20% silver nanoclusters in polymethacrylic acid on simulated dentin caries; its penetration depth and effect on surface hardness

The aims of this study were: To evaluate the surface hardness of simulated dentin caries lesions treated with either silver nanoclusters (AgNCls) synthesized in polymethacrylic acid (PMAA) or 38% silver diammine fluoride (SDF), as well as observe the penetration of the treatment solutions into the simulated caries lesions. Dentin blocks 4 mm thick obtained from caries-free third molars were sectioned and then simulated caries lesions on the occlusal dentin surfaces were created. Each specimen (n = 8) was divided into four sections: (A) treated with 20% AgNCls/PMAA; (B) treated with SDF 38% (FAgamin, Tedequim, Cordoba, Argentina); (C) sound tooth protected by nail-varnish during artificial caries generation (positive control); and (D) artificial caries lesion without surface treatment (negative control). AgNCls/PMAA or SDF were applied on the simulated lesions with a microbrush for 10 s, then excess removed. The surface hardness was measured by means of Vickers indentation test. To trace the depth of penetration, up to 400 μm, of silver ions, elemental composition of the samples was observed using EDX, coupled with SEM, and measured every 50 μm from the surface towards the pulp chamber. Laser Induced Breakdown Spectroscopy (LIBS) was also employed to trace silver ion penetration; the atomic silver line 328.06 nm was used with a 60 μm laser spot size to a depth of 240 μm. Student’s-t test identified significant differences between treatment groups for each depth and the Bonferroni test was used for statistical analysis of all groups (p < 0.05). Mean surface hardness values obtained were 111.2 MPa, 72.3 MPa, 103.3 MPa and 50.5 MPa for groups A, B, C and D respectively. There was a significant difference between groups A and C compared with groups B and D, the group treated with AgNCls/PMAA achieved the highest surface hardness, similar or higher than the sound dentin control. A constant presence of silver was observed throughout the depth of the sample for group A, while group B showed a peak concentration of silver at the surface with a significant drop beyond 50 μm. The 20% AgNCls/PMAA solution applied to simulated dentin caries lesions achieved the recovery of surface hardness equivalent to sound dentin with the penetration of silver ions throughout the depth of the lesion.

PENGARUH PROSES PACK NITRIDING TERHADAP ANGKA KEKERASAN PERMUKAAN, KEULETAN DAN STRUKTUR MIKRO PADA BAJA SS 400

The pack nitriding process is a process of increasing the surface hardness of steel by using nitrogen with the help of organic compounds as a nitrogen source in the process. The processed steel is put into a vessel which is usually made of ceramic, glass or aluminum along with a compound used as a nitrogen source. During heating,The organic compounds used in the analysis process are generally stable at temperatures up to 570 oC and removal times of 2 to 16 hours. The purpose of the pack nitriding process is to increase the surface hardness while remaining ductile inside. In this study, nitrogen was added using a pack nitriding process after which it was quenched using water. The elimination times used were 4 and 6 hours with temperature variations of 560°C, 580°C and 600°C and presenting nitrogen for the 150 gram pack nitriding process. The highest hardness value was obtained at 580 °C with a surface hardness value of 234.84 kg/mm2 with 4 hours of removal time. And the highest impact value was shown by the specimen without treatment of 158.3 Joules. The results of testing the chemical composition of the specimens without treatment and after the pack nitriding process showed that there was an increase in the nitrogen element.

Effect of denture cleansers on color stability and surface properties of denture base material containing titanium dioxide nanoparticles.

To investigate the effect of different denture cleansers on color stability, surface roughness, and hardness of polymethylmethacrylate (PMMA) infused with titanium dioxide nanoparticles (TiO2 NPs) at concentrations of 1% and 2% by weight on each. In this in vitro study, 90 disc-shaped specimens (10×10×2mm) were divided into 3 main groups: the non-containing nanoparticle group (0wt% concentration), 1wt% concentration, and 2wt% concentration TiO2 NPs groups. Each group was further assorted into 3 subgroups (n = 10): immersed in distilled water, oxygenating tablet (Corega), and 0.5% sodium hypochlorite. Color change, surface roughness, and hardness values were assessed after 90 and 180 days of storage. Color changes (∆E) were measured with a spectrophotometer (VITA, Easy Shade V, Germany) and assessed using the CIE L*a*b* colorimetric system and the American National Bureau of Standards (NBS = 0.92×∆E). The surface roughness and surface hardness values were measured using a profilometer device and Vickers hardness tester, respectively. First, ANOVA-repeated measurements were performed, followed by the Tukey test. The significance level in this study was considered 0.05. At all concentrations, there were significant differences in the mean color changes of samples immersed in cleansers compared to distilled water (p < 0.01). Moreover, hypochlorite caused a significant increase compared to Corega at 0wt% concentration after 90 days and at 1wt% concentration after 90 and 180 days. Evaluations also showed that the mean NBS values in all cleanser groups were in the range of appreciable change, except the water group. In addition, only hypochlorite changed the color higher than the clinically acceptable range (∆E >3.7). The mean roughness of samples immersed in hypochlorite at 0wt% concentration was significantly higher than the samples containing TiO2 NPs (p = 0.006). No significant difference was observed in surface roughness of samples containing different concentrations of TiO2 NPs immersed in different cleansers; however, hypochlorite increased the surface roughness of samples without TiO2 NPs compared to samples containing TiO2 NPs after 180 days. The immersion time in cleansers had a significant influence on the surface roughness and hardness while having no effect on the color. In general, the cleansers had a significant effect on color change in all groups compared to distilled water. The adverse effect of hypochlorite was more than Corega. The cleansers in the samples containing TiO2 NPs did not make a significant difference in surface roughness in comparison with the distilled water groups. Surface hardness of the samples was not affected in a steady pattern by the cleansers.

Evaluation of mechanical, optical, and fluoride-releasing properties of a translucent bulk fill glass hybrid restorative dental material.

Measure and compare the mechanical properties, translucency, and fluoride-releasing capabilities of EQUIA Forte HT against Fuji IX GP and ChemFil Rock. Ten specimens of each material were fabricated for compressive strength (CS), flexural strength (FS), and surface hardness analysis at 24 h and 7 days. The L*a*b* values were measured against a black-and-white background using a spectrophotometer to analyze the translucency parameter (TP). Fluoride release was recorded after 2 months of immersion in distilled water. The mean data was analyzed by 1- and 2-way ANOVA (α = 0.5). EQUIA Forte HT showed higher CS, surface hardness, and FS values (p < 0.05) compared with Fuji IX GIC, while no significant difference was found in FS values between EQUIA Forte HT and Chemfil Rock (p > 0.05). The EQUIA Forte HT exhibited significantly higher translucency in comparison to both ChemFil Rock (p < 0.001) and Fuji IX GICs (p < 0.05). An increase (p > 0.05) of fluoride release was observed for EQUIA Forte HT. The EQUIA Forte HT Glass-ionomer cements (GIC) offers enhanced translucency, improved strength, and enhanced fluoride-releasing properties compared to the traditionally used Fuji IX GIC and ChemFil Rock GICs. This material might have a wide range of clinical applications due to its improved strength and optical properties. Glass-ionomer dental restorative materials possess unique advantageous characteristics. However, its poor mechanical and optical properties have typically limited its clinical applications. Efforts to improve these properties have resulted in enhanced GICs. EQUIA Forte HT GIC offers enhanced mechanical and optical properties with potential applications in posterior and anterior restorative procedures.

Perbandingan Kekerasan Permukaan Resin Komposit Nanofiller Setelah Perendaman Dalam Obat Kumur Beralkohol Dan Non Alkohol

Tooth decay is a major problem for dental and oral health in the surrounding environment. Process Degenerative diseases that start in the enamel and spread to the dentin are part of a disease known as dental caries. Composite resin is a material used for restorations. One of the mechanical properties of nanofiller composite resin, namely surface hardness, can affect the durability of composite resin. The cause that can affect the surface hardness of the composite is the use of mouthwash. Mouthwash, both alcoholic and non-alcoholic, can help maintain healthy teeth and mouth. The aim of this research was to determine the comparison of the surface hardness of nanofiller composite resin after immersion in alcoholic and non-alcoholic mouthwash. Materials and methods used are Experimental Laboratories with the Post-test With Control Group Design research design used. A total of 30 nanofiller composite resin samples were soaked for 24 hours in three different groups, namely group I which received distilled water as a control, group II which received mouthwash with 21.6% alcohol, and group III which received mouthwash without 0% alcohol. The Vickers hardness test is the test method used. The results of this research are that the Kruskal-Wallis test and the Mann Whitney U follow-up test show that the surface hardness comparison is not significant for the nanofiller composite resin in the distilled water and alcohol mouthwash groups, namely (p-value&gt; 0.05), and the surface hardness comparison is significant. on nanofiller composite resin occurred in the alcoholic and non-alcoholic mouthwash immersion group (p-value &lt;0.05). Conclusion: There is a comparison of the immersion surface hardness of alcoholic and non-alcoholic mouthwash in nanofiller composite resin. Soaking alcoholic mouthwash causes the surface hardness value to be very low.

Effects of Various Beverages and Tooth Brushing on Microhardness of Restorative Materials Used in Pediatric Dentistry

Purpose. The objective of this study was to assess the impact of beverages and tooth brushing on the microhardness of different restorative materials. Materials-methods. Disk-shaped samples of compomer (Dyract XP), glass ionomer cement (GIC) (Ionofil Molar AC), and composite resin (Filtek Z250) were prepared. The samples were randomly allocated to four groups and conditioned in various beverages (cheery juice, cola, chocolate milk, and distilled water) for 3 hours per day over 60 days. Each group was further subdivided to a brushing and a non-brushing subgroup. In the brushing group, samples were brushed once daily with toothpaste and an electric toothbrush. The surface hardness of the samples was measured at baseline and after 60 days. Results. The microhardness of composite resin group increased in all solutions (p&amp;lt;0.05). The compomer group exhibited a decrease in microhardness after immersion in cola and cherry juice (p&amp;lt;0.05). The surface hardness of the GIC was measured to be lower in all solutions (p&amp;lt;0.05). Brushing had no effect on the microhardness in any of the groups (p&amp;gt;0.05) Conclusion. Filtek Z250 composite exhibited better surface hardness values than compomer and GIC. Cola and cherry juice decreased the microhardness of compomer and GIC.

Surface modification of grey cast iron by laser cladding for automotive brake disc application

In this research, Laser Cladding (LC) of three different alloys powders, two iron-based (AISI 4140 and SS420) and a Cobalt-based (Stellite 6) was performed on a Grey Cast Iron (GCI) substrate. The Stellite 6, SS420, and AISI 4140 cladding samples were tested against a semi-metallic composite brake pin for friction and wear study using a pin-on-disc friction test rig (under dry-sliding conditions). The surface wettability tests were performed on GCI, and cladding discs showed Stellite 6 and AISI 4140 were hydrophobic while SS420 and GCI were hydrophilic. Stellite 6, SS420, and AISI 4140 had surface hardness values of 542.16 HV1, 689.56 HV1, and 719.50 HV1, respectively. The friction test indicated that AISI 4140 and Stellite 6 cladding discs could produce a stable Coefficient of Friction (CoF) and friction layer coverage. SS420 could not maintain a constant CoF for the entire test duration as the plowing effect of the wear particles damaged the friction layer created on its surface. Stellite 6's average CoF value was closest to that of the GCI disc, whereas AISI 4140 and SS420 were found to have a higher average CoF. The LC on grey cast iron reduced its wear rate, with AISI 4140 being the most wear-resistant cladding, followed by SS420 and Stellite 6, respectively. All three cladding layers exhibited three-body abrasive wear, with the rolling mechanism dominating the AISI 4140 surface and sliding on the remaining two.

Mechanical Properties of 3D-Printed Occlusal Splint Materials.

Data regarding the mechanical properties of three-dimensionally (3D) printed materials for occlusal splint manufacturing are scarce. The aim of the present study was to evaluate the flexural strength and surface hardness of modern 3D-printed occlusal splint materials and compare them with two control groups, namely, milled and conventional cold-polymerized occlusal splint materials. A total of 140 rectangular specimens were manufactured for the present study. The specimens were prepared in accordance with the International Organization for Standardization standards (ISO 20795-1:2013). Five 3D-printed (NextDent Ortho Rigid, Dental LT Clear, Dentona Flexisplint, Cosmos Bite Splint, and ProArt Print Splint), one milled (ProArt CAD Splint), and one cold-polymerized (ProBase Cold) occlusal splint materials were used to determine flexural strength and surface hardness values. The three-point flexure test was used for the determination of flexural strength values, while Vickers hardness was measured to determine surface hardness. Ten specimens (n = 10) of each material were tested using these procedures. One-way ANOVA and Tukey's post-hoc test were used to analyze the obtained results (α = 0.05). The values of flexural strength ranged from 46.1 ± 8.2 MPa to 106 ± 8.3 MPa. The Vickers hardness values ranged from 4.9 ± 0.5 VHN to 20.6 ± 1.3 VHN. Significant differences were found among the tested materials (p < 0.0001). The milled and cold-polymerized materials yielded higher values for both flexural strength (only one 3D-printed resin had comparable results to cold-polymerized acrylics) and surface hardness. There are differences in the mechanical properties of the various tested occlusal splint materials. The flexural strength of most of the 3D-printed materials and their surface hardness values are still inferior when compared to the milled or cold-polymerized materials.

Surface roughness and surface hardness changes in composite resin provisional crown before and after brushing with whitening toothpaste

Objective: To determine the surface roughness and surface hardness difference in composite resin provisional crown before and after brushing with whitening toothpaste.&#x0D; Material and Methods: This was a pre- and post-test group design experimental study. In this study, the sample was a composite resin provisional crown based on bis-acryl. The number of samples in this study was 32 samples, 16 for the surface roughness test and the other 16 for the surface hardness test. Each sample was brushed using a V8-Brushing Machine Modified, then tested for surface roughness and hardness using a Profilometer and Vickers Hardness Tester.&#x0D; Results: The paired T test was used to analyze the results statistically. There was a significant difference between the groups before and after brushing with whitening toothpaste. (p&lt;0.05).&#x0D; Conclusion: After simulated brushing with whitening toothpaste, there was a change in the the provisional crown material surface roughness and hardness value.

Catalytic infrared blanching and drying of carrot slices with different thicknesses: Effects on surface dynamic crusting and quality characterization

This study investigated the effects of catalytic infrared (CIR) as an emerging dry-blanching and dehydration technique on carrot quality and textural properties, and the dynamic surface crusting during blanching was studied under the optimal CIR conditions. Results showed that the surface crusting was observed under all selected conditions and expressed as surface hardness values of carrot slices, which increased over CIR time and slice thickness, reaching 25.29%–38.20% of fresh tissue. Micrographs displayed that cell structure of the carrot surface crust collapsed, and cell deformation degree decreased from the surface to the inside tissue. The cell quantitative parameters were extracted using image processing, and the information on the surface crust of carrot slices was visible through the cell area, perimeter, roundness, and elongation factor. Results showed that the crust cell area and perimeter were higher than the non-crust part, while the roundness and elongation factor was lower than the non-crust tissue. Industrial relevanceCatalytic infrared (CIR) heating, an emerging dry-blanching and dehydration technique, is employed in various fruits and vegetables and has gained more attention due to its prompt attributes of high efficiency and energy-saving. The findings of this study explored the texture properties of carrot slices subjected to CIR treatment, especially the formation mechanism of the surface crusting due to thermal processing, which can provide basis and assistance for the CIR application in the fruit and vegetable processing industry and for regulating the practical producing conditions.

Investigation of mechanical, tribological and magnetic properties after plasma nitriding of AISI 316L stainless steel produced with different orientations angles by selective laser melting

In this study, AISI 316L stainless steel samples were produced with different orientations (0°, 45°, and 90°) using selective laser melting (SLM). In addition, plasma nitriding of the samples produced with SLM was performed at 400 °C for 4 h. The effect of different orientation on the structural, mechanical, tribological, and magnetic properties of 316L stainless steel was investigated. The same measurements also were made after the plasma nitriding process. The results showed that the phase composition and microstructure of the non-nitriding and nitridied samples were affected from the built orientation. Especially the XRD peaks shifted to the left with a decrease in the orientation angle. It was obtained that the highest modified layer thickness was measured from the samples produced with an angle of 0°. It was observed that the surface hardness, residual stress, wear resistance and antimagnetization tendency values of nitridied samples were higher than the non-nitriding samples. Furthermore, these values tended to increase with the decrease in build orientation angles.

The Effects of Cross-Linking Agents on the Mechanical Properties of Poly (Methyl Methacrylate) Resin.

Cross-linking agents are incorporated into denture base materials to improve their mechanical properties. This study investigated the effects of various cross-linking agents, with different cross-linking chain lengths and flexibilities, on the flexural strength, impact strength, and surface hardness of polymethyl methacrylate (PMMA). The cross-linking agents used were ethylene glycol dimethacrylate (EGDMA), tetraethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol diacrylate (TEGDA), and polyethylene glycol dimethacrylate (PEGDMA). These agents were added to the methyl methacrylate (MMA) monomer component in concentrations of 5%, 10%, 15%, and 20% by volume and 10% by molecular weight. A total of 630 specimens, comprising 21 groups, were fabricated. Flexural strength and elastic modulus were assessed using a 3-point bending test, impact strength was measured via the Charpy type test, and surface Vickers hardness was determined. Statistical analyses were performed using the Kolmogorov-Smirnov Test, Kruskal-Wallis Test, Mann-Whitney U Test, and ANOVA with post hoc Tamhane test (p ≤ 0.05). No significant increase in flexural strength, elastic modulus, or impact strength was observed in the cross-linking groups compared to conventional PMMA. However, surface hardness values notably decreased with the addition of 5% to 20% PEGDMA. The incorporation of cross-linking agents in concentrations ranging from 5% to 15% led to an improvement in the mechanical properties of PMMA.

Synthesis and characterisation of single and duplex ZnO/TiO2 ceramic films on additively manufactured bimetallic material of 316L stainless steel and Ti6Al4V

Selective laser melting (SLM), one of the Laser Powder Bed Fusion (LPBF) additive manufacturing methods, has enabled the layered production of Ti6Al4V/316L layered samples, thanks to the layer-by-layer construction. Although 316L and Ti6Al4V are used in many engineering applications, their wear performance is limited. This study aims to improve the tribological and electrochemical properties of Ti6Al4V/316L layered samples. Thus, ZnO, TiO2 monolayer, composite, and ZnO/TiO2, TiO2/ZnO multilayer ceramic films on Ti6Al4V/316L layered surface sample, were coated via the sol-gel dip-coating process. The structural, morphological, and tribological properties of ZnO-TiO2 ceramic films were analyzed via x-ray diffractometer, Scanning Electron Microscopy (SEM), and 3D profilometer. The tribological properties of these coatings were examined using a reciprocating tribo-tester, and the electrochemical properties of samples were evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Structural and mechanical results indicated that ZnO and TiO2 films (monolayer, composite, and multilayer-coated) have higher surface roughness and hardness values than additively manufactured Ti6Al4V/316L layered models. Both single and multilayer ZnO and TiO2 ceramic-coated films improved the wear resistance of the Ti6Al4V/316L substrate. Also, The best tribological and corrosion resistance was acquired for the multilayer film (ZnO/TiO2) among all the coated models.

Different responses of wheel–rail interface adhesion and wheel surface damage induced by an out–of–round wheel tread

The out–of–roundness of wheel treads are an inherent degradation characteristic of the wheels of railway vehicles, and the interface behaviour of the wheel and rail caused by out–of–roundness features has essential research value in high–speed train running safety and quality. Sliding–rolling contact wear testing was conducted to evaluate the effect of the out–of–round wheel on the wheel–rail damage behaviour, by using a twin–disc setup. The effects of four wheels, three wheels of different eccentricities and one normal wheel were taken as a control group. The characteristics of the wheel–rail interface adhesion, wheel surface damage and compressive residual stress (CRS) distribution were compared and analysed. The results showed a dramatic increase in the fluctuation amplitude of the wheel–rail vertical force of the eccentric wheels, and the adhesion coefficient of the wheel–rail interface significantly decreased. Furthermore, eccentric wheels dramatically accelerate the wear loss of the rail used as a counterpart during wheel–rail rolling contact. The surface damage behaviour of the eccentric wheels is obviously different along the circumferential direction, and non–uniform wear was observed. The damage mechanism of the worn surface presented varying characteristics, which could be divided into a severely damaged zone (located at the maximum of the rolling radius rmax) and a slightly damaged zone (located at the minimum of the rolling radius rmin). The surface contact stress of the severely damaged zone was high, this finding can be explained by the extremely rough worn surface caused by the severe fatigue delamination characteristics and the initiation and propagation of fatigue cracks in the severely damaged zone. Furthermore, the values of surface hardness and residual stress were relatively low. By contrary, an adhesion layer was observed on the worn surface of the slightly damaged zone. The adhesion layer protects worn surface in the slightly damaged zone was relatively flat, and the CRS was relatively high.

Pengaruh Variasi Holding Time pada Proses Pack Carburizing dengan Arang Tempurung Kelapa Barium Carbonat Terhadap Sifat Fisik dan Mekanik Baja ST 42

Iron-based production machine components are chosen to support productivity. Steel is a metal material that is easily found on the market, but it has not fulfilled the desires of consumers in the market. This steel can be hardened by heat treatment (heat treatment). The surface treatment process is carried out to obtain the desired hardness, this can be done by increasing the carbon (C) element in the steel material, the carbon content in the standard steel structure is 0.3% - 0.59% the carbon content will have an effect. on hardness, one way to increase the element carbon (C) in steel and increase the hardness on its surface is by carburizing. This research will examine the hardness level of low carbon steel by using a pack carburizing process with different times of 2; 2.5 and 3 hours and the quenching process with pure water media.. The purpose of this study was to determine the effect of holding time on the pack carburizing process with coconut shell charcoal - barium carbonat on the hardness value of ST 42 steel. Besides that for effect of holding time on the pack carburizing process with coconut shell charcoal on the microstructure. There are differences in the surface hardness and microstructure values ​​ before and after the carburizing process. Where the highest hardness value occurs at a holding time of 3 hours with a hardness value of 872.9 HVN or an increase of 382% of the raw material and is supported by the dominance of the martensite phase which is more and more evenly distributed. Compared to the ST 42 steel raw material before the pack carburizing process was carried out, the hardness value was 174.8 HVN. A dominant microstructure consisting of a ferrite phase and a little bit of pearlite dominance.

Characteristics of ASTM A36 steel mechanical properties in pack carburizing with carburizing agent coconut shell charcoal and goat bone powder mixed

In the study the specimens were ASTM A36 low carbon steel pack carburizing at 950℃, soaking time variations of 1, 2 and 3 hours. The carburizing agent is a mixture of coconut shell charcoal and goat bone powder (Capra aegagrus hircus). The size of the powder is 100 mesh, with variations in weight percentage between goat bone powder and coconut shell charcoal: 10%:90%, 20% : 80%, and 30% : 70%. Furthermore, the impact test, hardness, microstructure test and composition test were carried out, to determine the mechanical properties of the specimens. The results of the study show, soaking time and the composition of the carburizing agent affect the mechanical properties of the specimen The lowest impact toughness of 0,0576 joules/mm2 was obtained by the specimen at a soaking time of 1 hour, the composition of the carburizing agent (% wt goat bone powder: coconut shell charcoal) 20% : 80%. The highest surface hardness value was 854.734 Kg/mm2 at 3 hours soaking time with 10%:90% carburizing media composition. The results of microstructure observations showed that in specimens treated with pack carburizing ferrite structure, pearlite turned into martensite.