• Korean Journal of Materials Research
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• v.26 no.3
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• pp.130-135
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• 2016

To alloy high melting point elements such as boron, ruthenium, and iridium with copper, heat treatment was performed using metal oxides of $B_2O_3$, $RuO_2$, and $IrO_2$ at the temperature of $1200^{\circ}C$ in vacuum for 30 minutes. The microstructure analysis of the alloyed sample was confirmed using an optical microscope and FE-SEM. Hardness and trace element analyses were performed using Vickers hardness and WD-XRF, respectively. Diffusion profile analysis was performed using D-SIMS. From the microstructure analysis results, crystal grains were found to have formed with sizes of 2.97 mm. For the copper alloys formed using metal oxides of $B_2O_3$, $RuO_2$, and $IrO_2$ the sizes of the crystal grains were 1.24, 1.77, and 2.23 mm, respectively, while these sizes were smaller than pure copper. From the Vickers hardness results, the hardness of the Ir-copper alloy was found to have increased by a maximum of 2.2 times compared to pure copper. From the trace element analysis, the copper alloy was fabricated with the expected composition. From the diffusion profile analysis results, it can be seen that 0.059 wt%, 0.030 wt%, and 0.114 wt% of B, Ru, and Ir, respectively, were alloyed in the copper, and it led to change the hardness. Therefore, we verified that alloying of high melting point elements is possible at the low temperature of $1200^{\circ}C$.

• Journal of Environmental Science International
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• v.16 no.6
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• pp.677-682
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• 2007

This study was performed to provide the basic information on characteristics of groundwater pollution in Gyeongsan city. Forty two groundwater samples were collected, and pH, DO, COD, $NH_3-N,\;NO_3^--N$, T-N, $PO_4^{3-}-P$, Cl, Ca, Mg, hardness, evaporate residues and others were investigated. And, ANOVA analyses were carried out to reveal the differences in water pollution indicator values of by industry, commerce/residence and agriculture areas. The results were as follows. 1. The mean values of pH, DO, COD, $NH_3-N,\;NO_3^--N$, T-N, $PO_4^{3-}-P$, Cl, evaporate residues, Ca and hardness were 6.9, $7.9mg/\ell,\;0.4mg/\ell,\;2.44mg/\ell,\;2.73mg/\ell,\;6.06mg/\ell,\;0.82mg/\ell,\;32.72mg/\ell,\;381.67mg/\ell,\;41.53mg/\ell,\;177.17mg/\ell$, respectively. 2. As groundwater became deeper, the values of Cl, Ca, Mg, Na, hardness and evaporate residues remarkably increased, but those of COD, $NH_3^--N,\;NO_3^--N,\;NO_2^-N$, T-N decreased. 3. The values of COD, Cl, Ca, Mg, Na, hardness and evaporate residues were very high in industrial area, and those of $NH_3-N,\;NO_2^--N$, T-N were very high in commercial/residential area, and those of $NO_3^--N$ were a little high in agricultural area. 4. The correlations between depth and each value of Mg, Na, Fe, hardness and evaporate residues were highly positive, and those between DO and each value of Mg, Cu, Fe, hardness and evaporate residues were highly negative. 5. According to ANOVA analyses, the differences in three area groups (industry, commerce/residence and agriculture) on the values of $NH_3-N$, T-N, evaporate residues, hardness, Ca, Mg, K and Fe were significant at 1% level.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.460-468
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• 2022

Due to its high electrical conductivity, low contact resistance, good weldability and high corrosion resi-stance, gold is widely used in electronic components such as connectors and printed circuit boards (PCB). Gold ion salts currently used in gold plating are largely cyan-based salts and non-cyanic salts. The cya-nide bath can be used for both high and low hardness, but the non-cyanide bath can be used for low hardness plating. Potassium gold cyanide (KAu(CN)₂) as a cyanide type and sodium gold sulfite (Na₃[Au(SO)₃]₂) salt as a non-cyanide type are most widely used. Although the cyan bath has excellent performance in plating, potassium gold cyanide (KAu(CN)₂) used in the cyan bath is classified as a poison and a toxic substance and has strong toxicity, which tends to damage the positive photoresist film and make it difficult to form a straight side-wall. There is a need to supplement this. Therefore, it is intended to supplement this with an eco-friendly process using sodium sulfite sodium salt that does not contain cyan. Therefore, the main goal is to form a gold plating layer with a controllable hardness using a non-cyanide gold plating solution. In this study, the composition of a non-cyanide gold plating solution that maintains hardness even after annealing is generated through gold-palladium alloying by adding thallium, a crystal regulator among electrolysis factors affecting the structure and hardness, and changes in plating layer structure and crystallinity before and after annealing the correlation with the hardness.

• Journal of the Korean institute of surface engineering
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• v.38 no.2
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• pp.79-82
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• 2005

This study investigated the effect of nitriding on the hardness and adhesion properties of $TiB_2$ coatings. Inductively coupled plasma (ICP) was used for both nitriding and deposition. By applying ICP, H13 steel was nitrided at a high rate of $50\;{\mu}m/hr$. After nitriding, a Fe4N compound layer or a diffusion layer was formed according to the hydrogen/nitrogen ratio. Both layers could improve the load-bearing capacity of the substrate by increasing the substrate hardness. The adhesion of the $TiB_2$ coatings increased to $\~30N$ after nitriding, but the hardness of the coating was lowered to 20-30 GPa. However, the adhesion of the $TiB_2$ coatings with a high hardness (>60 GPa) could not be improved substantially by nitriding due to the large difference in hardness between the coating and the substrate. The grain size of the $TiB_2$ coating was larger on the nitrided substrates, resulting in a decrease in the hardness of the coating.

• Journal of the Korean Society for Heat Treatment
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• v.37 no.4
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• pp.182-187
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• 2024

To improve and control the mechanical properties of low alloy steel, the influence of quenching and tempering process conditions was investigated. In the case of quenching heat treatment, a comparison was made between the conventional method of heating to the austenite region followed by single quenching and a method involving double quenching, followed by high-temperature tempering. It was observed that specimens subjected to double quenching exhibited significantly finer tempered microstructures compared to those subjected to conventional quenching, resulting in noticeably higher hardness. Additionally, a study was conducted to investigate the variation in hardness with changes in tempering temperature and time after the same conventional quenching treatment. As expected, an increase in tempering temperature or time led to a decrease in hardness, and the correlation between hardness and the Hollomon-Jeffe Parameter was confirmed. It was also observed that during high-temperature tempering, the size of carbides significantly increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.707-708
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• 2008

• KIEAE Journal
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• v.16 no.3
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• pp.83-88
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• 2016

Purpose : This study aimed to verify the surface hardness and water repellency of earth paint manufactured with earth, a natural material, and provide the results as basic data for paint made with natural materials. Method : After presenting the accurate manufacturing methods for basic materials for paint, the authors conducted and analyzed experiments to evaluate surface hardness and water repellency, fundamental performance indicators for paint, based on different mixture ratios. From the results of the experiment to assess the surface hardness of flour-based earth paint, we observed high surface hardness only after painting the specimen three times. Since potato starch-based earth paint has higher viscosity than its flour-based counterpart, the former did not paint well on the first occasion, resulting in low surface hardness. After painting two or more times, however, it was observed to have higher surface hardness than flour-based earth paint. Result : It was found that at least three iterations of painting was required to obtain high surface hardness of potato starch-based earth paint. Furthermore, the results of the water resistance experiment of earth paint suggest that the use of environment-friendly finishing materials coupled with boiled linseed oil will mitigate the drawbacks of earth paint. The experiment with one-year-old specimens also demonstrated similar water repellent characteristics, which indicates that the performance will improve once the paint has dried for a sufficient period of time.

• Journal of Ocean Engineering and Technology
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• v.13 no.3 s.33
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• pp.92-99
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• 1999

High temperature and pressure materials in power plant are degraded by creep damage, if they are exposed to constant loads for long times, which occurs in load bearing structures of pressurized components operationg at elevated temperatures. Many conventional measurement techniques such as replica method, electric resistance method, and hardness test method for measuring creep damgage have been used. So far, the replica method is mainly used for the inspection of high temperature and pressure components. This technique is, however, restricted to applications at the surface of the testpieces and cannot be used to material inside. In this paper, ultrasonic evaluation for the detection of creep damage in the form of cavaties on grain boundaries or intergranular microcracks were carried out. And the absolute measuring method of quantitative ultrasonic velocity technique for Cr-Mo material degradation was analyzed. As a result of ultrasonic tests for crept for specimens, we founded that the sound velocity was decreased as increase of creep life fraction(${phi}c$) and also, confirmed that hardness was decreased as increase of creep life fraction(${phi}c$).

• Journal of Powder Materials
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• v.21 no.2
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• pp.97-101
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• 2014

The 304 stainless steel powders were prepared by high energy ball milling and subsequently sintered by spark plasma sintering, and the microstructural characteristics and micro-hardness were investigated. The initial size of the irregular shaped 304 stainless steel powders was approximately 42 ${\mu}m$. After high energy ball milling at 800 rpm for 5h, the powders became spherical with a size of approximately 2 ${\mu}m$, and without formation of reaction compounds. From TEM analysis, it was confirmed that the as-milled powders consisted of the aggregates of the nano-sized particles. As the sintering temperature increased from 1073K to 1573K, the relative density and micro-hardness of sintered sample increased. The sample sintered at 1573K showed the highest relative density of approximately 95% and a micro-hardness of 550 Hv.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.105-106
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• 2007

Microstructure and hardness of metallic powder of Cu was studied after high pressure torsion (HPT) with 10 torsions and high pressure of 6 GPa. The size Cu grain decreases drastically after HPT and reaches the nano size range. During HPT, Cu powder increases hardness and Hall-Petch hardening, due to the decreasing grain size. In this study, effect of HPT on the hardness of Cu powders and consolidation with Nanocrystalline of the work reported here. The results indicated that Cu powder has a beneficial effect on homogeneous deformation, reducing grain size.