• Journal of Korea Foundry Society
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• v.42 no.3
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• pp.153-160
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• 2022

The effect of thickness on the microstructure and the mechanical properties of centrifugal cast 625 was investigated. Centrifugal cast 625 with various thickness of 10, 17 and 50mm showed partially columnar grained structure 8, 12.3 and 18.5mm respectively from the outer surface. Secondary dendrite arm spacing in the columnar grains slightly increased with increasing casting thickness. Tensile strength of the columnar region was similar regardless of casting thickness. Solidification behavior of the columnar grained region is similar to that of directional solidification, thus solidification rate in the centrifugal cast tube was extrapolated from the secondary dendrite arm spacing data of the directionally solidified material. The equiax grained region formed interior of the thick castings. The tensile strength of the equiaxed region showed the average value of the columnar region which is presumably originated from the grain structure rather than secondary dendrite arm spacing.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.108-108
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• 2009

Precipitation hardening nickel base alloys strengthened by intermetallic compounds are extensively used to manufacture on the components of the hot section of gas turbine engines. To ensure structural stability and maintenance of strength properties for a long time, nickel alloys are normally subjected to complex alloying with elements to form ${\gamma}'$(gamma prime). Such alloys have a limited weldability, are normally welded in high temperature. However, laser welding have a merit that applies in room temperature as easy control of welding parameter and heat input. In this study, $CO_2$ laser welding is applied on STS304 plate with good ductility and precipitation hardening nickel base alloy (GTD111DS) used blade material. Also, several welding parameters are applied on powder, power and travel speed. There are no cracks in Rene 80 and IN 625 powder when STS304 plate is used. But IN 625 powder has no cracks and Rene 80 have some cracks in welds with GTD111DS substrate. Adjusting of welding parameter is tried to apply Rene 80 having a good strength compare to IN 625. In the result of adjusted welding parameter, optimized welding parameters are set with low power, low feed rate and high welding speed. Tensile strength of GTD111DS substrate with Rene 80 powder is same and over than the one of base metal in room temp and high temp($760^{\circ}C$).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.177-183
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• 2005

In this work, Inconel 600, Inconel 625 and Haynes 230 are welding using Nd:YAG laser and electron bear. These heat-resistant alloys are typically used for the liquid thruster. To examine, the affects of experimental parameters on weld ability, the plate welding of these materials were carried out using both Nd:YAG laser and electron bear. Also, the micro-structure, micro-hardness, and tensile strength of the specimens were analyzed. from the analysis of the experimental results of laser and electron beam welding, we have obtained the optimal welding conditions.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.540-547
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• 2001

This study has evaluated the wear behavior of PTA (Plasma Transferred Arc) Inconel 625 and Stellite 6 overlays on Nimonic 80A substrate. Nimonic 80A alloy was also included for comparison. In order to evaluate the wear performance, three-body abrasive wear test and pin-on-disk dry sliding wear test were performed. Microstructural development during the solidification of deposits is also discussed. Wear test results show that the wear rate of Stellite 6 deposit is lower than that of Inconel 625 deposit and Nimonic 80A. The sliding wear resistance of overlay deposits follows a similar trend to the abrasive wear resistance, but for Nimonic 80A. The main wear mechanisms were abrasive wear for Inconel 625 deposit, adhesive wear and delamination for Stellite 6 deposit in pin-on-disk dry sliding wear test and ploughing in three-body abrasive wear test. Cross sectional examinations of the worn surface of pin specimens after pin-on-disk dry sliding wear test implies that the plastic deformation near worn surface has occurred during the wear testing.

• Journal of Powder Materials
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• v.27 no.3
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• pp.219-225
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• 2020

The directed energy deposition (DED) process of metal 3D printing technologies has been treated as an effective method for welding, repairing, and even 3-dimensional building of machinery parts. In this study, stainless steel 316L (STS316L) and Inconel 625 (IN625) alloy powders are additively manufactured using the DED process, and the microstructure of the fabricated STS316L/IN625 sample is investigated. In particular, there are no secondary phases in the interface between STS316L and the IN625 alloy. The EDS and Vickers hardness results clearly show compositionally and mechanically transient layers a few tens of micrometers in thickness. Interestingly, several cracks are only observed in the STS 316L rather than in the IN625 alloy near the interface. In addition, small-sized voids 200-400 nm in diameter that look like trapped pores are present in both materials. The cracks present near the interface are formed by tensile stress in STS316L caused by the difference in the CTE (coefficient of thermal expansion) between the two materials during the DED process. These results can provide fundamental information for the fabrication of machinery parts that require joining of two materials, such as valves.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.6
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• pp.625-631
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• 2015

The hardness of surface treated magnesium alloy was evaluated using laser induced breakdown spectroscopy. The surface of the specimen was hardened mechanically, and the hardness profiles were measured using a traditional measurement technique. A laser beam was irradiated to generate a plasma, and the peaks of the components of the specimen were analyzed. A wavelength of 333.66 nm and 293.65 nm were selected as the atomic and ionic peaks, respectively. The ratios of the ionic peak to the atomic peak were obtained so as to compare the hardness profile. As the depth increased, the ratio decreased. These results are in good agreement with the previous hardness measurement results. It can be considered that this technique could be applied for remote and time-efficient hardness measurement.

• Journal of Welding and Joining
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• v.24 no.3
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• pp.49-54
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• 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.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.158-160
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• 2006

Super alloys are typically used for the liquid thruster in the aerospace industry. In this work, The bead-on-plate welding of Inconel 600, Inconel 625 and Haynes 230 using Nd:YAG laser are studied, in order to examine the effects of experimental parameters on their weldability. The micro-hardness and tensile strength of the specimens are also analyzed, to obtain the optimal welding conditions.

• Korean Journal of Materials Research
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• v.4 no.6
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• pp.620-625
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• 1994

We recently showed from the neutron diffraction and extended X-ray absorption fine structure studies the structural evidence for the formation of an amorphous phase in immiscible Cu-Ta system subjected to mechanical alloying. In a system with a positive heat of mixing like Cu-Ta, we consider it necessary to confirm the formation of an amorphous phase not only from the structural studies but also from a change in the electronic properties. We show the electronic evidence for the formation of the chemical bonding between the unlike atoms Cu and Ta for the 120 h-milling sample through changes in superconducting transition temperature and X-ray photoemission spectroscopy valence band structure.

• Transactions of Materials Processing
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• v.18 no.8
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• pp.625-632
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• 2009

The influence of the subsequent-annealing(SA) temperature on the plasma electrolytic oxidation(PEO)-treated Mgbased alloy was investigated in terms of surface properties associated with hardness and corrosion. For this purpose, a series of the SA treatments were performed on the PEO-treated samples at four different temperatures, i.e., 100, 150, 200, and $250^{\circ}C$ for 10 hrs. When compared to the sample without SA, the samples annealed at temperatures higher than $200^{\circ}C$ showed a difference in surface morphology due to the volume expansion accompanied by the dehydration reaction where the part of $Mg(OH)_2$ changed into MgO, working as harder phase. From the results of nano-indentation tests, the applied loads of the samples were seen to increase with increasing SA temperatures. However, the electro-chemical and corrosion properties of the sample annealed at $150^{\circ}C$ were higher than those of the samples annealed at three temperatures.