• 열처리공학회지
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• 제17권2호
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• pp.94-100
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• 2004

In order to improve the wear resistance of Ti-6Al-4V alloy, plasma carburization treatment was newly carried out without consumption of its good specific strength and fatigue life over the temperature. Effect of the plasma carburization was analyzed and compared with the non-treated alloy by microstructural observation, structure characterization and mechanical test. The plasma treated alloy formed a carburized layer of about $150{\mu}m$ in depth from the surface, where a fine and hard particles of TiC and $V_4C_3$ were homogeneously dispersed through the layer. The steady-static creep behaviors of Ti-6Al-4V alloy, using the constant stress creep tester, were investigated over the temperature range of $510{\sim}550^{\circ}C$(0.42~0.44Tm) and the stress range of 200~275 MPa. Stress exponent(n) was decreased from 9.32 of non-treatment specimen to 8.95 of carburized, however, the activation energy(Q) increased from 238 to 250 kJ/mol with the same condition as indicated above. From the above results, it can be concluded that the static creep deformation for Ti-6Al-4V alloy was controlled by the dislocation climb over the ranges of the experimental conditions.

• 열처리공학회지
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• 제28권1호
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• pp.24-31
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• 2015

In this study, a simulation was used to derive an optimal process of heat treatment with carburizing, and compared the derived result with SCr420HB helical gear in heat treatment with carburized quenching process about a change of the quenching method. The optimal carburizing process time is derived by the simulation with the theoretical time. The process has been performed by oil quenching and salt quenching method. Through the comparison of the results from the simulation(Hardness, effective case depth hardened by carburizing treatment and deformation) and the actual process, analyzed the error value of each quenching. And it verified the applicability of the simulation.

• 한국재료학회지
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• 제12권5호
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• pp.341-346
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• 2002

In order to improve the low wear resistance of Ti-6Al-4V alloy, plasma carburization treatment was newly carried out without consumption of its good specific strength and fatigue life over the temperature. Effect of the plasma carburization was analyzed and compared with the non-treated alloy by microstructural observation, structure characterization and mechanical property test. The plasma treated alloy formed a carburized layer of about 150$\mu\textrm{m}$ in depth from the surface, where a fine and hard particles of TiC and $V_4C_3$ were homogeneously dispersed through the layer. It was also found that an increase of the wear resistance, fatigue life and hardness, due to the hard and fine dispersoids.

• 열처리공학회지
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• 제13권1호
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• pp.21-26
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• 2000

This study deals with effects of heat-treatment on the fatigue strength of SNC815 spur gears. The test gears are heat-treated by two different treatments. After carburization, one group of the test gears is quenched directly, while the other group is fumace cooled, reheated then quenched. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester. The S-N curves are obtained and illustrated. By comparing the estimated strength with the experimental results, the validity of the previous experimental formula, presented by the author for estimating the fatigue strength of carburized gears, was discussed on these tested gears.

• 대한기계학회논문집A
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• 제36권9호
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• pp.971-978
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• 2012

진공침탄법은 이산화탄소의 발생이 없는 친환경적인 열처리 방식으로 알려져 있다. 그러나 진공침탄법은 탄화수소 가스(메탄, 프로판)를 노내에 직접 공급하여 열분해하는 과정을 거침으로써 노내에 그을음이 발생하여 안정적인 조업이 불가능한 단점이 있다. 최근에는 이러한 단점을 극복하기위한 불포화 탄화수소인 아세틸렌가스를 이용한 진공침탄법이 활발히 연구되고 있다. 본 논문에서는 아세틸렌가스를 이용한 진공침탄방식의 침탄 및 확산 시간을 변수로 하여 여러 가지 조건에서 열처리를 진행한 후 가스침탄 열처리된 소재와 기계적 성질을 비교 분석하여 이산화탄소 무 배출 진공침탄 열처리 방법의 활용가능성을 확인하였다. 연구결과 본 연구에서 시도된 진공침탄법은 가스침탄에서 나타나는 입계산화층이 발생하지 않았으며 경도 값은 진공침탄 시험편의 유효경화 깊이가 29.8% 크게 나타났으며 인장강도는 가스침탄보다 10%낮게 나왔으나 허용치를 충분히 만족하는 수준이었다.

• 열처리공학회지
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• 제19권5호
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• pp.262-269
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• 2006

The development of eco-friendly low pressure carburizing system with high pressure gas quenching(LPC-GQ, 500kg/charge) led to new stage in the fundamental case-hardening treatments. This is due to its ability to provide tighter tolerances on the carburizing process with notable reductions in distortion of the carburized and hardened workpiece. This system is characteristics by high uniformity and reproducibility of heat treatment results, absence of an intergranular oxidation layer, carburizing of complex shapes, reduced cycle time, low operating costs, simplified production, eliminate post washing, and reduced grinding costs.

• 대한금속재료학회지
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• 제50권6호
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• pp.433-438
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• 2012

Strength change in ultra low carbon steel carburized at $880^{\circ}C$ and $930^{\circ}C$ for 10, 30, 60 and 120 minutes was investigated. The results were analyzed by a tensile test, chemical composition analysis, optical microscopy and scanning electron microscopy. Stress in the 0.5% strain specimen in the tensile test increased as the time treated at $880^{\circ}C$ and $930^{\circ}C$ increased, because the carbon diffusion layer and the martensite of the specimen increased with increasing treatment time. Martensite was found in the ferrite region in the specimen treated at $880^{\circ}C$, which is attributed to grain boundary diffusion.

• 한국안전학회지
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• 제14권4호
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• pp.13-19
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• 1999

This study deals with effects of heat-treatment on the bending fatigue of SCM420 spur gears. The test gears are heat-treated by two different treatments. After carburization, one group of the test gears is quenched directly, while another group is furnace cooled, reheated then quenched. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic serve-controlled pulsating tester. The S-N curves are obtained and illustrated. By comparing the estimated strength with the experimental results, the validity of the previous experimental formula, presented by the authors for estimating the fatigue strength of carburized gears, was discussed for these tested gears.

• 열처리공학회지
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• 제9권4호
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• pp.261-270
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• 1996

Boriding is one of the chemical methods to achieve the case hardening of steel as well as nitriding or carburizing. The surface layer of the borided steel shows higher hardness and exhibits better resistance to corrosion or fatigue than the nitrided or carburized steel. The great majority of previous studies were confined to mild steel or some alloy steel. To enlarge the application, ductile cast iron (DCI) as a material for boriding has been tried in this study. Thus, sliding wear test has conducted using a pin-on-disc machine to compare between borided DCI and mild steel in fluidized bed furnace. The results show that the wear resistance of borided DCI is improved. Especially it is more efficient in the case of occurence of the mechanical wear.

• 열처리공학회지
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• 제15권6호
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• pp.269-271
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• 2002

For the investigation of the hardness profiles and distortion characteristics of SCM415 steel, test pieces of SCM415 steel were gas and vacuum carburizing treated. The hardness profiles and distortion characteristics of vacuum and gas carburized SCM415 steel show different results. Vacuum carburizing can offer more improved hardness profiles than alternate methods of carburizing. Compared to alternate methods of carburizing, vacuum carburizing can offer improved mechanical properties and reduced cycle times of the process.