Papers by Keyword: Hardness

Abstract: The chemical composition of the metal and carbide phase, hardness, and common mechanical properties of cast iron, ICH28H2 cast iron, a type of high-chromium white cast iron, and the dependence of hardening, annealing, and tempering process types were studied. Therefore, annealing and hardening heat treatments were employed, and the results were compared to measurements in the as-cast state. The metal matrix exhibited content within the range of 16.8% to 19.7% Cr and 71.9% to 76% Fe, while the carbide phase showed 63.4% to 64.7% Cr and 23% to 24.8% Fe. The Cr carbide in high Cr white iron primarily appeared as (Fe, Cr)7C3 type, leading to the calculated chemical formula of the eutectic carbide as (Fe2Cr5)C3. The as-cast white iron displayed a hardness of 53 HRC, which increased marginally to 56.2 HRC after hardening. This suggests that the 28% Cr white iron alloy does not exhibit a significant hardness enhancement compared to the cast state, attributed to its high Cr content. The hardness of the metal phase directly influences the overall hardness change of the alloy, while the carbide hardness is dependent on its Cr content. Abrasive wear studies revealed that 28% Cr white cast iron exhibited superior wear resistance in the as-cast state compared to the hardened state, aligning with research indicating that cast iron demonstrates optimal wear resistance in its cast state.

Abstract: TIG (Tungsten Inert Gas) welding has more and more application options. To always create new ways of optimization, a more in-depth study of the effects on the components subject to joining is necessary. The paper includes a study on the hardness resulting in the specific areas of the welded joint, using TIG welding with high frequency pulsed arc, applied to join some stainless-steel plates. The relative variation of the hardness was determined and analysed, in correlation with the process parameters. The study is part of the research on obtaining a good energy efficiency in the welding process, based on the requirements imposed on the quality of the joints.

Abstract: In the present study, it is aimed to investigate the influence of quench rate on the hardness and electrical conductivity that obtained after artificial aging by using Jominy End Quench test method. The Jominy End Quench test bars were solution heat treated at 560°C for 3 hours. After solution heat treatment, water, spray, and air quenching medias were used in order to obtain different quench rates. After the quench, quench rate determination, hardness and electrical conductivity measurements were performed for three different quenching medias. Then, artificial aging heat treatment were applied to all samples at 180°C for 8 hours to understand the effect of quench rate on aging process. The relationship between quench rate, hardness and electrical conductivity have presented.

Abstract: In this study, the impact of heat treatment and Equal Channel Angular Pressing (ECAP) processing routes on refining the microstructure, hardness, and corrosion resistance of Al-7.5% S alloy in a 3.5% NaCl solution was examined. The alloy underwent T5 and T6 heat treatments, followed by ECAP processing via routes A and Bc in a mold with a channel angle of 120° at room temperature. The results indicate that dendritic α-Al grains transformed to globular and fiber shapes after processing routes Bc and A, respectively. Both processing routes fragmented coarse and brittle Si particles into smaller sizes in the eutectic phase. The use of a combination of heat treatment and the Equal Channel Angular Pressing (ECAP) process significantly improved the hardness and corrosion resistance of the samples. The hardness of the heat-treated samples increased considerably from 68 to 116 and 129 HV after three and four passes, respectively. Reducing the area ratio between the noble silicon particles and the less noble eutectic aluminum phase greatly enhances the resistance of alloy to pitting corrosion.

Abstract: Ti-6Al-4V ELI (Ti64 ELI) has been widely used as metal-based biomedical implants as it has ductility and fracture toughness that surpasses the commercial Ti-6Al-4V. Casting process is one of the most cost-effective ways to produce near-net-shape Ti64 ELI implants. Nevertheless, previous study has found that grain coarsening occurred in an as-cast Ti64 ELI, which lowered its mechanical properties. To improve the properties, in this work, the samples were heat-treated in three different temperatures that varied above and below β-transus temperature for 30 minutes and then water-quenched. Following the solution treatment, each sample was artificially aged in 500 °C for four hours and left cooled inside the furnace. Hardness Vickers, microstructure, and XRD analyses were conducted to determine the effect of solution treatment regarding to its phase and properties. The result of microstructure observation showed transformation in different temperatures. The highest result of hardness value was obtained in the solution treatment variation of 1050 °C, which was 474 HVN. The XRD pattern showed that the intensity of the α/α’ phase of temperatures 850 °C, 950 °C, and 1050 °C were 92.84%, 72.65%, and 86.78%, respectively, with the intensity of the β phase were 7.16%, 27.35%, and 13.22%. The corrosion resistance performance was measured by the potentiodynamic polarization method using Ringer’s solution with pH ± 7,4 and the best corrosion resistance result was 0.093 mmpy in variation 950 °C as β phase was predominantly appeared in this temperature.

Abstract: Wire-arc additive manufacturing is a method of 3D printing metal using welding techniques. However, due to heat, the mechanical properties of the deposited material may be affected. Various methods have been proposed to mechanically improve the properties. In this study, cold deformation was introduced to enhance the properties. The effects of a few parameters, including welding speed, wire feed rate, heat input, thickness ratio, and types of material, were studied. Based on the result, the hardness, tensile, and wear properties of the manufactured part improved, while other properties, like impact toughness, had a lower value. Based on the preliminary result, cold deformation shows potential alternatives for part repair or reconstruction of worn or broken parts.

Abstract: Titanium Nitride coating has attracted much interest in increasing the hardness of aluminum alloys. This study aims to investigate the effect of Ar: N gas mixture and time on increasing the hardness of aluminum alloys using DC sputtering. Preparation of TiN thin films on aluminum alloy substrates using flowing gas mixture parameters and time. First, the layer of TiN was deposited on the sample with a gas mixture of 90Ar:10N; 80Ar:20N; 70Ar:30N; and 60Ar:40N (%) for 60 minutes. Then the optimum gas mixture that produces the highest surface hardness is used in the second process with time variations of 30, 60, 90, and 120 minutes. The results showed that the highest hardness was achieved in a gas mixture of 70Ar:30N and 60 minutes. The TiN phase formed on the aluminum surface was identified by XRD, while the surface morphology was observed by SEM. Compared with untreated samples, the hardness of treated samples increased significantly.

Abstract: To minimize the cost of production and enhancement pipe quality, this research aims to gain insights into the physical and mechanical characteristics of high-performance polypropylene random filled with rigid inorganic calcium carbonate particles at various content levels, with a specific focus on how the toughness of PPR changes. Virgin Polypropylene Random PPR, a new material extracted from a homopolymer polypropylene, is used as a matrix with 10, 20, 30, 40, and 50 wt. % of CaCO₃. The density, melt flow rate, tensile strength, tensile strain, modulus of elasticity, and hardness are used to evaluate the quality of the material. The results showed that the density, the modulus of elasticity, and the hardness increased with increasing the percentage of CaCO₃. As the percentage of CaCO₃ increased, the melt flow rate decreased. The tensile strength and strain increased to 28.7 MPa and 533.25%, respectively at 20 wt.% of CaCO₃, with 14.8% and 6.65% reaching gains compared to the virgin PPR (25 MPa and 500%). The enhancement of the mechanical properties is thanks to the presence of stiffer and rigid particles of CaCO₃ that act as a reinforcing agent. Moreover, when CaCO₃ is well dispersed, it forms a strong bond with the polypropylene matrix, and facilitates the transfer of stress from the matrix to the fillers, resulting in increased stiffness. The optimum percentage of CaCO₃ to add into the inner layer of extruded PPR pipes is at a composition of the filler of 20 wt. %.

Abstract: Nanotitania is a well-acceptable material in biomedical applications due to its excellent biocompatibility. However, its other performances in terms of physical properties, mechanical properties and specific wear rate have been the keen interest of researchers. The study aims to modify dental composite formulation by adding nanotitania filler in different mass fractions and study to investigate its influence on physical and mechanical properties. A conventional monomer matrix consisting of Bisphenol A-Glycidyl methacrylate (BisGMA), Urethane dimethacrylate (UDMA), Triethylene glycol dimethacrylate (TEGDMA), Camphor Quinone (CO), Ethyl-4-dimethylaminobenzoate (EDMAB) was first added and modified with varying nanotitania filler fractions (0,0.5,1,1.5 wt. %). The performance of newly formulated composites was investigated in four major parameters like apparent porosity, hardness, compressive strength and specific wear rate. All tests are performed as per ISO4049 standard which are requirements for fabrication, characterization, direct/indirect restoration of dental composite, inlays, onlays, veneers, crowns and bridges. Specific wear rate was estimated using pin on disk tribometer under constant load of 20N. Due to its extremely hard and brittle nature, the micro-hardness and compressive strength of resin composite on adding 0.5 wt.-% of nanotitania filler fraction (DC0.5TiO₂) were increased by 68% and 16% respectively. Using a pin on disc tribometer, a wear assessment has been performed and it was found that under constant wear parameters and distilled water environmental conditions, the specific wear rate was decreased by 26 % on adding 0.5 wt.-% mass fraction of nanotitania. Nanotitania indicated excellent performance based on mechanical and wear properties and hence, it can be suggested to use nanotitania as a novel filler of dental composite for the replacement of other non-biocompatible ceramic filler.

Abstract: Asbestos-based brake shoes are being faded out due to worries that they may cause cancer; as a result, research for suitable replacements is an essential area of focus. Research on agricultural by - products such as flax fibres, rockwool, aramid fibres, banana fibres, and nut shells from palm trees have been used to develop a number of potential replacements for asbestos. Palm wastes, which are picked for the study since there was a paucity of previous research on the topic, are obtained from agricultural waste fibres. As part of this investigation, a composite material was created, and a number of tests were carried out in order to investigate the wear and durability of a set of unique composites. The novel composites contained 20% epoxy resins, 10 % carbon, 15% CaCO₃, 30–45% PKS, and 10–25%Al₂O₃ respectively. The results obtained showed that the finer the sieve size the better the properties.