Papers by Keyword: Hardness

Abstract: There are two major heating methods used in industrial situations. One is furnace heating which is popular for mass production as it hardens the steel uniformly. The other is induction heating which is energy saving but hardens the steel unevenly. We developed a combined heat treatment method, furnace-induction heating (FIH), and observed the material structure using picral and nital etching.

Abstract: For better mechanical properties and lifetime of sintered products, it is suggested that an improvement can be made by a combination of mechanical-and chemical-surface treatments. In this study, the effect of deep-rolling on surface properties and microstructure is investigated. It is found that both compactness and hardness is improved by deep-rolling process where high force is applied. The outer surface hardness can be doubled when the deep-rolling is applied prior to carburizing. Nonetheless, a reduction in the thickness of the martensite-transformed layer due to an increment of applied force is observed.

Abstract: This research investigated mechanical degradation of powder injection moulded SiC_p-reinforced aluminium composite subjected to moderate temperature exposures. Aluminium composite of 20 vol.% SiC_p reinforcement was produced by powder injection moulding and sintering at 680°C, followed by 500°C solution treatment plus 150°C for 6 hours artificial aging, and subsequent exposures at 100, 200 and 300°C for 10 and 100 hours. It was found that short-term exposure for 10 hours provided increasing hardness with increasing exposure temperature, while long-term exposure for 100 hours led to an opposite result. The maximum micro Vickers hardness was obtained at 182.2 H_v for Al-SiC_p composite exposed at 300°C for 10 hours. Tensile strength was however found deleterious with increasing both exposure temperature and time. The maximum tensile strength was achieved at 191.2 MPa for Al-SiC_p composite exposed at 100°C for 100 hours. The formations of AlN, Mg₂Si and Al₂Cu were observed in both age-hardened and as-exposed conditions. Furthermore, the highest temperature exposure at 300°C and extended exposure time at 100 hours resulted in the lowest hardness and tensile properties due possibly to the loss of coherency of precipitates. SiC_p clusters were the main cause of the tensile failure.

Abstract: The research is to investigate influence of sonication treatment on the morphologi and mechanical properties of bioplastic filler nanoclay with different nanoclay concentration. The bioplastic was prepared using blending method among bioplastic, glycerol, and nanoclay with assistance of sonication treatment of 30 mins. Structural characterization of bioplastic was examined using scanning electron microscopy (SEM), mechanical properties using durumeter Shore A, tensile strength and the physical properties using density. SEM evidence on a bioplastic basis. Hardness of bioplastic with addition of nanoclay 5.0% (b/b) and sonication treatment produce bioplastic with maximum hardness properties increased to 76.24 Shore A, tensile strength of 13.5 and Young’s modulus of 47, as well as the added density of 1.238 g/cm³. Nanoclay 7.5% (b/b) upwards will experience decreased hardness and experience agglomerate and debonding.

Abstract: Nitride hard coatings Al_25.5Cr₂₁Si_3.5N were deposited on WC-Co substrates with a different thickness and a negative substrate bias voltage by the LAteral Rotating Cathodes Arc technology. The nanoindentation tests were performed for analysis of AlCrSiN coatings in order to determine the most promising combination of parameters for subsequent machining. On the basis of results of nanohardness measurement and Ratio H/E*, which represents the resistance to plastic deformation and cracking, deposition conditions were selected for coating of turning cemented carbide inserts. For the evaluation of coating adhesion to substrate, Mercedes adhesion test was used. Chip forming tests and long-term tool life tests were performed for determination of cutting parameters (cutting speed, feed rate and depth of cut) for AlCrSiN coated cemented carbide inserts when machining austenitic stainless steel material.

Abstract: This paper studies the effect of different solution temperature and quenching medium on Microstructure and hardness of Mg-9Li-4Al-1Zn-0.5Y alloy by means of optical microscope (OM), X-ray diffraction (XRD) and hardness testing. The results show that in the solution process, the higher of the solution temperature is, more of the second phase dissolved in β phase. In the quenching process, the higher of the cooling rate is, more of the second phase dissolved in the β phase precipitates from the super-saturation β matrix, which can greatly weaken the solution strengthening effect. The hardness of the investigated alloy reaches its highest value with solution treatment at 648K and water-quenched treatment, increased from 58HB to 108HB.

Abstract: The effect of grain size in nanocrystalline alloys is difficult to analyze because challenges of controlling a number of other microstructure factors. This paper designed and prepared a series of multilayered films with Al-Zr crystalline layers of different thickness but with amorphous layers of identical thickness. In these multilayered films, the heights of columnar crystals in crystalline layers were controlled from 5 to 160 nm and their diameters were kept at 10 to 15 nm, independent of their heights. This design achieved the control of grain size, independent from other microstructure factors. The analysis of mechanical properties of these multilayered films showed that the inverse Hall-Petch phenomenon also exists in Al-Zr nanocrystalline alloys. The critical grain sizes of deviation from the Hall-Petch relationship and the inverse Hall-Petch phenomenon are approximately 40 nm and 10 nm respectively. These mechanical behaviors of nanocrystalline alloys are similar to those reported in pure metals.

Abstract: Work is focused on study of workability changing of heat resistant nickel-based Ni-15Co-10Cr alloy produced by selective laser sintering from metal powder. Experimental research of HRC hardness changing was provided on plate samples 2х10х30 mm after sintering and typical heat treatment for this alloy. Heat treatment was: annealing at temperature of 1,000oС during 1.5 hours, and then at the temperature of 1,180oC for 2.5 h – 3 h. After that samples were treated in a furnace for 50 – 60 minutes at the temperature of 1,050oС. Then they were cooled-off to the temperature of 1,000oС during 50 – 60 minutes. After that they were further quenched at ambient temperature. After quenching the samples were subjected to ageing at the temperature of 850oC during 3, 6, 9, 12 and 15 hours. The bending and measurement of triangle height was proposed for work ability assessment of samples. Increased hardness was found with duration of ageing. Work ability grew up with duration of ageing but where was a gap of workability for 9 hours ageing. Calibration of sintered parts and samples are recommended to perform after quenching and ageing at 850oC no longer 6 hours.

Abstract: AISI 304 is a type of stainless steel used for load bearing implants due to relatively low cost. However, its mechanical properties and corrosion resistance must be improved to the level of AISI 316L, cobalt-based alloys, titanium and titanium alloy properties. Its fatigue characteristic is also one of the most important criteria have to be evaluated to achieve the overall service performance requirements, when this material subjected to dynamic load. High surface hardness may delay fatigue crack initiation and decrease corrosion rate because these two processes initiated at surface layer. The purpose of this research is to investigate the change in mechanical and corrosion characteristics of AISI 304 due to shot peening processes.Surface treatment with shot peening process were done by regulating the variation time for 0, 5, 10, 20, 30 and 40 minutes at the firing pressure of 7 bar; using 0,6 mm steel ball with hardness of 40-50 HRC. Firing distance between the nozzle with the specimen surface is 100 mm. Surface hardness was tested using indentation load of 10 grams for 10 seconds. Pitting corrosion test of treated AISI304 and non treated AISI316L was conducted in intravenous Otsu-RL brands as corrosion media. Pitting corrosion was performed using cyclic polarization methodThe hardness of surface layer increase with increasing shot-peening time. According to increase of length of shot-peening time from 0, 5, 10, 20, 30 and 40 minutes the hardness of these specimen increase to 241, 404, 418, 437, 481 and 496 VHN, respectively. The pitting corrosion rate tend to significantly decrease with increasing of shot peening time. According to increase of length of shot peening time from 0, 5, 10, 20, 30 and 40 minutes the pitting corrosion rate of these specimen also decrease to 0.853, 0.619, 0.086, 0.017, 0.116 and 0.036 mpy, respectively. Pitting corrosion rate of AISI316L is 0.042 mpy. Best pitting corrosion rate of treated AISI304 is 2.5 times smaller than that of non treated AISI316L. Therefore, shot-peening could be used to increase hardness number and reduce pitting corrosion rate, significanly.

Abstract: In this study, the main thermal, structural and mechanical properties of optical glass materials were investigated by conventional glass melting method. The thermal properties of optical glass materials are important in that they constitute the first steps towards the investigation of other physical and chemical properties. According to the thermal properties of the material, the glass transition temperature, T_g, increases for different glass compositions. The XRD, XRF, FT-IR and hardness properties of the obtained optical glass materials were determined experimentally in terms of their structural and mechanical properties for their suitability for potential applications. XRD spectra obtained without heat treatment of glass materials show that the material structure is amorphous. In the same way, Vicker’s hardness values of the glassware increase relative to the different glass compositions, resulting in a result that the material is influenced by the bonds between the constituents of the chemical components.