• Journal of Welding and Joining
• /
• v.19 no.5
• /
• pp.540-547
• /
• 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 Korea Foundry Society
• /
• v.22 no.6
• /
• pp.304-308
• /
• 2002

The new Cu-Zr-Ti-Ni-Pd amorphous alloy system has been introduced and manufactured using melt-spinning and Cu-mold die casting methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties of the alloys were examined. The reduced glass transition temperature(Trg = Tg/Tm) and the supercooled liquid region(${\Delta}$Tx = Tx-Tg) of $Cu_{49}Zr_{30}Ti_{10}Ni_5Pb_6$ alloy were 0.620 and 57 K respectively. $Cu_{49}Zr_{30}Ti_{10}Ni_5Pb_6$ amorphous alloy was produced in the rod shape with 2mm diameter using the Cu-mold die casting. The hardness value of the amorphous bulk alloy was 432 DPN.

• Journal of Korea Foundry Society
• /
• v.10 no.6
• /
• pp.485-494
• /
• 1990

• Journal of Korea Foundry Society
• /
• v.10 no.5
• /
• pp.361-371
• /
• 1990

• Nuclear Engineering and Technology
• /
• v.41 no.1
• /
• pp.107-112
• /
• 2009

Corrosion of nickel-base alloys (Hastelloy C-276, Inconel 625, and Inconel X-750) in $500^{\circ}C$, 25MPa supercritical water (with 10 wppb oxygen) was investigated to evaluate the suitability of these alloys for use in supercritical water reactors. Oxide scales formed on the samples were characterized by gravimetry, scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicate that, during the 1000h exposure, a dense spinel oxide layer, mainly consisting of a fine Cr-rich inner layer ($NiCr_{2}O_{4}$) underneath a coarse Fe-rich outer layer ($NiFe_{2}O_{4}$), developed on each alloy. Besides general corrosion, nodular corrosion occurred on alloy 625 possibly resulting from local attack of ${\gamma}$" clusters in the matrix. The mass gains for all alloys were small, while alloy X -750 exhibited the highest oxidation rate, probably due to the absence of Mo.

• Journal of Powder Materials
• /
• v.25 no.4
• /
• pp.331-335
• /
• 2018

This study investigates the directional recrystallization behavior of Ni based oxide dispersion strengthened (ODS) alloy according to the zone annealing velocity. The zone annealing temperature is set as $1390^{\circ}C$, while the zone velocities are set as 2.5, 4, 6, and 10 cm/h, respectively. The initial microstructure observation of the as-extruded sample shows equiaxed grains of random orientation, with an average grain size of 530 nm. On the other hand, the zone annealed samples show a large deviation in grain size depending on the zone velocities. In particular, grains with a size of several millimeters are observed at 2.5-cm/h zone velocity. It is also found that the preferred orientation varies with the zone annealing velocity. On the basis of these results, this study discusses the role of zone velocities in the directional recrystallization of Ni base ODS alloy.

• Journal of Powder Materials
• /
• v.1 no.2
• /
• pp.145-152
• /
• 1994

Atomizing mode and powder characteristics of CuA1Ni base shape memory alloy in rotating disk atomization were investigated in accordance with disk materials and additional elements. Produced powders were classified into two types of spherical and flake shape. In the case of CuAlNiBTi and CuAlNiZr alloy, high yield rate and fine powder were obtained. This tendency was same when we used oxide coated disks. We concluded that this results were steno from the wetting characteristics change between molten metal and disk surface. Especially, due to the reactive properties of Ti and Zr with ceramic disk, the change of atomizing appearance and powder characteristics were noticeable.

• Progress in Superconductivity
• /
• v.7 no.1
• /
• pp.64-68
• /
• 2005

We fabricated Ni-based alloy substrates for YBCO coated conductor using powder metallurgy. Tungsten and copper were selected as alloy elements due to their mutual solubility to the base element of nickel. The alloying elements were mixed with nickel using ball milling and dried in air. The powder mixtures were packed in a rubber mold, cold isostatic pressed 200 MPa and made into rods. The compacted rods were sintered at $1150^{\circ}C$ for 6 hours for densification. It was confirmed by neutron diffraction experiment that W and Cu atoms made complete solid solution with Ni. Lattice constant of nickel alloy increased by $0.004{\AA}$ for 1at. $\%$ W in Ni-W alloy, $0.0006{\AA}$ for 1 at. $\%$ Cu in Ni-W-Cu alloy.

• Journal of Welding and Joining
• /
• v.15 no.5
• /
• pp.46-55
• /
• 1997

This study has evaluated the liquation cracking behavior in the heat affected zone of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). 304 and 310S austenitic stainless steels were also included for comparison. In addition, the mechanism of liquation cracking in the HAZ was postulated based on the extensive microstructural examinations with SEM, EDAX and TEM. The liquation cracking resistance of Ni base alloys was found to be far inferior to that of austenitic stainless steels. The liquation cracking of Incoloy 825 and Inconel 718 was believed to be closely related with the Laves-austenite(Ti rich in 825 and Nb rich in 718) and MC-austenitic eutectic phases formed along the grain boundaries by constitutional liquation and incipient melting under rapid welding thermal contraction. Further, liquation cracking resistance of the HAZ was dependent not only upon the type and amount of low melting phases but also on the grain size.

• Transactions of Materials Processing
• /
• v.24 no.1
• /
• pp.44-51
• /
• 2015

The current study seeks to examine the effects of V and C additions on the mechanical and low thermal expansion properties of a high strength invar base alloy. The base alloy (Fe-36%Ni-0.9%Co-2.75%Mo-0.7Cr-0.23Mn-0.17Si-0.3%C, wt.%) contains $Mo_2C$ carbides, which form as the main precipitate. In contrast, alloys with additions of 0.4%V+0.3%C (alloy A) or 0.4%V+0.45%C (alloy B) contain $Mo_2C$+[V, Mo]C carbides. The average thermal expansion coefficients of these high strength invar based alloys were measured in the range of $5.16{\sim}5.43{\mu}m/m{\cdot}^{\circ}C$ for temperatures of $15{\sim}230^{\circ}C$. Moreover, alloy B showed lower thermal expansion coefficient than the other alloys in this temperature range. For the mechanical properties, the [V, Mo]C improved hardness and strengths(Y.S. and T.S.) of the high strength invar base alloy. T.S.(tensile strength) and Y.S.(yield strength) of hot forged alloy B specimen were measured at 844.6MPa and 518.0MPa, respectively. The tensile fractography of alloy B exhibited a ductile transgranular fracture mode and voids were initiated between the [V, Mo]C particles and the matrix. Superior properties of high strength and low thermal expansion coefficient can be obtained by [V, Mo]C precipitation in alloy B with the addition of 0.4%V and 0.45%C.