• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집C
• /
• pp.627-632
• /
• 2001

Nimonic 80A superalloy with high-temperature strength and high corrosion-resistance is used in jet engine for aircraft, gas turbine for power plant and marine diesel engine, etc. To develop the manufacturing process of exhaust valve for large diesel engine using Nimonic 80A, various mechanical tests, such as hot compression, microstructure and hardness test have been performed. This results effectively used to set the reasonable forging conditions while hot forging of Nimonic 80A superalloy. Open die and closed die forging experiments are carried out from ESR ingot and finally get a good shaped exhaust valve product.

• 소성∙가공
• /
• 제14권4호
• /
• pp.384-391
• /
• 2005

The nickel-based alloy Nimonic 80A possesses the excellent strength, and the resistance against corrosion, creep and oxidation at high temperature. Its products are used in aerospace engineering, marine engineering and power generation, etc. Control of forging parameters such as strain, strain rate, temperature and holding time is important because change of the microstructure in hot working affects the mechanical properties. Change of the microstructure evolves by recovery, recrystallization and grain growth phenomena. The dynamic recrystallization evolution has been studied in the temperature range of $950\~1250^{\circ}C$ and strain rate range of $0.05\~5s^{-1}$ using hot compression tests. The metadynamic recrystallization and grain growth evolution has been studied in the temperature range of $950\~1250^{\circ}C$ and strain rate range $0.05,\;5s^{-1}$, holding time range of 5, 10, 100, 600 sec using hot compression tests. Modeling equations are proposed to represent the flow curve, recrystallized grain size, recrystallized fraction and grain growth phenomena by various tests. Parameters in modeling equations are expressed as a function of the Zener-Hollomon parameter. The modeling equation for grain growth is expressed as a function of the initial grain size and holding time. The modeling equations developed were combined with thermo-viscoplastic finite element modeling to predict the microstructure change evolution during hot forging process. The grain size predicted from FE simulation results is compared with results obtained in field product.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2009년도 추계학술대회 논문집
• /
• pp.84-88
• /
• 2009

The nickel-based alloy Nimonic 80A possesses strength, and corrosion, creep and oxidation resistance at high temperature. The exhaust valves of low speed diesel engines are usually operated at temperature levels of 400-$600^{\circ}C$ and high pressure to enhance thermal efficiency and exposed to the corrosion atmosphere by the exhaust gas. Also, the exhaust valve is subjected to repeated thermal and mechanical loads. So, the nickel-based alloy Nimonic 80A was used for the large exhaust valve spindle. It is composed a 540mm diameter head and a 125mm diameter stem. It is developed large products by hot closed-die forging. Manufacturing process analysis of the large exhaust valve spindle was simulated by closed die forging with hydraulic press and cooled in air after forging. The preform was heated to $1080^{\circ}C$ Numerical calculation was performed by DEFORM-2D, a commercial finite element code. Heat transfer can be coupled with the deformation analysis in a non-isothermal deformation analysis. Mechanical properties of the large exhaust valve spindle were evaluated by the variety of tests, including microstructure observation, tensile, as well as hardness and fatigue tests, were conducted to evaluate the mechanical properties for head part of exhaust valve spindle.

• 소성∙가공
• /
• 제32권3호
• /
• pp.107-113
• /
• 2023

The importance of dual-fuel engines has increased for reducing CO₂ emissions. However, the low operating temperature of this engine may induce low-temperature corrosion at combustion parts, which reduces the engine service life. To overcome this problem, NiCr38Al4 alloy was developed for valve spindle, but the cost of this alloy is expensive due to its high Cr content. For reducing the manufacturing cost of valve spindle, in the present work, NiCr38Al4 alloy was welded with Nimonic80A alloy by conducting friction welding. The tensile test results show that the strength of friction-welded specimens follows the properties of the lower-strength parent materials, without severe cracks at the interface. The large shear strain and frictional heat from friction welding not only reduce grain size but also induce solute element diffusion at the interfacial region. Because of the low Cr diffusivity compared with Ti, Cr carbides were not observed in the Nimonic80A matrix, while Ti carbides were distributed in both the Nimonic80A and SNCrW matrices.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 추계학술대회논문집
• /
• pp.301-304
• /
• 2004

Friction welding was used to weld the turbine wheel and shaft and have a good welding quality. Friction welding was conducted an the two dissimilar material, Nimonic 80A and SNCrW. The control of friction welding process parameter such as flywheel energy, interface temperature, amount of upset have an effect on the mechanical properties of the welded joint. FE simulation can be a useful tool to optimize the weld geometry and process parameters. Flash shape and thickness weld is consistent with the simulated results. Process analysis was performed by the commercial code DEFORM 2D. Mechanical property of weld joints was evaluated by microstructure, chemical component, tensile, impact, hardness test so on.

• Journal of Welding and Joining
• /
• 제24권3호
• /
• pp.49-54
• /
• 2006

The Plasma Transferred Arc (PTA) overlaying method is lately introduced as one of the most useful surface modification method of the engine component. In this paper, the characteristics of the Co-base and Ni-base super alloy overlay layers by PTA method were investigated through the metallurgical, abrasive and cavitation erosion test. Experimental results showed that the abrasive wear resistance of the Co-base Stellite 6 overlayer was the most superior and followed in order of Nimonic 80A, Inconel 625 and Inconel 718. However, the cavitation erosion characteristic of the Stellite 6 overlayer was the most inferior and it was better in order of Inconel 625, Inconel 718 and Nimonic 80A.

• Journal of Advanced Marine Engineering and Technology
• /
• 제22권5호
• /
• pp.660-669
• /
• 1998

In this paper the Hardness and Electro-chemical corrosion of the Nimonic 80A superalloy were studied. It aging heat treatments was carried out at $650^{\circ}C$, $700^{\circ}C$, $750^{\circ}C$,$800^{\circ}C$ and $850^{\circ}C$ with different time of 20min , 30min 1hour, 2hours, 4hours, and 16hours additionally 64hours and 128hours at $650^{\circ}C$. The obtained results were as follows; 1. As aging temperature increased the time for the maximum hardness was reduced from 128hours at $650^{\circ}C$ to 30min at $850^{\circ}C$ whereas the highest hardness was reduced from Hv 381 at $650^{\circ}C$ to Hv 321 at $850^{\circ}C$. 2. In the Electro-chemical corrosion test as a function of aging heat treatment time and tem-perature the corrosion potential was reversely proportional to Hardness which indicated the effects of ${\gamma}/{\gamma}'$ coherency of base material and precipitate. 3. Initiation point of the pitting was observed at grain boundary twin boundary and near${\gamma}'$ pre-cipitates. The results of composition analysis by EDS at this point indicated that sulphur originat-ed from 1N $H_2SO_4$ solution was found in depletion at the grain boundaries and the pit which arouse in the near precipitates were lack of Al Ti and Ni which are the main element of ${\gamma}'$ The depletion of such element was cause breakdown of passive film.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2001년도 춘계학술발표대회 개요집
• /
• pp.245-247
• /
• 2001

In this study, the effects of dilution on the wear behavior of PTAW (Plasma Transferred Arc Welding) Inconel 625, Inconel 718 and Stellite 6 overlays on Nimonic 80A were investigated. Inorder to evaluate the wear performance, two-body and three-body abrasive wear test, and dry sliding wear test were performed. According to wear tests, the wear rate of deposit with dilution 30% was higher than that of dilution 10% by 10%, and it was also found the plastic deformation near worn surface.

• Journal of Welding and Joining
• /
• 제2권1호
• /
• pp.18-24
• /
• 1984

With the use of a new method the deformation mechanism of high-temperature-brazed joints can be obtained in a very short time. For that purpose a SEM(Scanning Electron Microscope) was equipped with a high temperature tensile testing machine. By means of SEM-investigation the damage behaviour of high-temperature-brazed joints is exa mined at elevated temperature. Based on these it is possible to make a qualification of the influence over single parts on the damage beginning and behaviour in dependence of temperature. This shall be shown exemplarily for the high temperature material NiCr20TiAl (Nimonic 80A).

• Journal of Advanced Marine Engineering and Technology
• /
• 제29권8호
• /
• pp.938-945
• /
• 2005

The microstructure evolution in hot forging process is composed of dynamic recrystallization during deformation as well as grain growth during dwell time. Therefore, the control of forging parameters such as strain, strain rate. temperature and holding time is important because the microstructure change in hot working affects the mechanical properties. Modeling equations are developed to represent the flow curve. grain size. recrystallized volume fraction and grain growth phenomena by various tests. The developed modeling equations were combined with thermo-viscoplastic finite element modeling to predict the microstructure change evolution during hot forging process. The large exhaust valve spindle (head diameter of 512mm) was simulated by closed die forging with hydraulic press and cooled in air after forging. The preform was heated to each 1080 and 1150$^{\circ}C$. Numerical calculation was performed by DEFORM-2D. a commercial finite element code. Heat transfer can be coupled with the deformation analysis in a non-isothermal deformation analysis. In order to obtain the fine and homogeneous microstructure and good mechanical properties in forging. the FEM would become a useful tool in the simulation of the microstructure development. In forging, appropriate temperature, strain and strain rate and rapid cooling are required to obtain the fine grain microstructure The optimal forging temperature and effective strain range of Nimonic 80A for large exhaust valve spindle are about 1080$\∼$l120$^{\circ}C$ and 150$\∼$200$\%$.