• Journal of the Korean institute of surface engineering
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• v.44 no.1
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• pp.1-6
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• 2011

A NiW functional alloy plating was investigated as variables of metal ion concentration, complexing agent, temperature, pH and applied current density. Even if numerous studies on reaction mechanism of NiW induced codeposition were carried out during couples of decade, it has not been acceptable reaction mechanism. This study was focused on the effect of the plating variables on the alloy composition in the NiW alloy plating. Applied current density could control mainly the alloy composition rather than other plating variables. It has also been confirmed that the functional alloy plating such as layered or gradient plating was possible by controlling applied current density.

• Journal of Powder Materials
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• v.5 no.1
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• pp.42-49
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• 1998

A study on the improvement of the impact energy in 93W heavy alloy with a Ni/Fe ratio of 9/1 has been carried out as a function of heat treatment temperature. The obtained results were compared to that of the traditional alloy system in which the Ni/Fe ratio is 7/3 or 8/2. With increasing heat treatment temperature from 1150 to 125$0^{\circ}C$, the impact energy of the alloy with the Ni/Fe ratio of 9/1 is remarkably increased from 42 to 72 J, which is higher than that of traditional alloy, up to 118$0^{\circ}C$ and then saturated. Fracture mode was also changed from brittle W/W boundary failure to W cleavage. The temperature showing the dramatic shrinkage by dilatometric anaysis of the heavy alloy with Ni/Fe ratio of 9/1 was found to be 1483 $^{\circ}C$, which is higher than that (146$0^{\circ}C$) of the heavy alloy with Ni/Fe ratio of 7/3. Auger Electron Spectroscopy showed that the segregation of impurities, such as S, P, and C in W/W grain boundary was considerably decreased with increasing heat treatment temperature from 1150 to l18$0^{\circ}C$. From the above results, it was found that the impurity segregation in W/W grain boundary played an important role on the decrease of impact properties, and the heat treatment temperature should be appropriately chosen, as considering the Ni/Fe ratio of the alloy, in order to get good impact properties.

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

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.28-29
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• 2006

The magnetic properties of a series of both annealed and as-rolled Ni-$W_y$ alloy tapes with compositions y = 0, 1, 3, and 5 at.%, were studied. To compare with Ni-W alloys, the magnetic properties of a series of both annealed and as-rolled $[Ni_{97at.%}W_{3at.%}]_{100-x}Cu_x$ alloy tapes with compositions x = 0, 1, 3, 5 and 7 at.%, were studied, as well. Both the isothermal mass magnetization M(H) of a series of samples, such as both Ni-W and [Ni-W]-Cu alloy tapes, at different fixed temperatures and M(T) in fixed field, were measured using a PPMS-9 (Quantum Design). The degree of ferromagnetism of Ni-$W_y$ alloys have reduced as W-content y increases. Both the saturation magnetization $M_{sat}$ and Curie temperature $T_c$ decrease linearly with W-content y, and both $M_{sat}$ and $T_c$ go to zero at critical concentration of $y_c$ ~ 9.50 at.% W. The effect of Cu addition on both the saturation magnetization $M_sat$ and Curie temperature $T_c$ decrease linearly with Cu-content x in $[Ni_{97at.%}W_{3at.%}]_{100-x}Cu_x$ alloy tapes with compositions x = 0, 1, 3, 5, and 7 at.%. The results confirm that [Ni-W]-Cu alloy tapes can have much reduced ferromagnetism as Cu-content x increases.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.106-108
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• 2003

We fabricated Ni and Ni-W alloys for use as a substrate in YBCO coated conductor applications and evaluated the effect of W in Ni on texture, microstructure and surface morphology, and hardness of substrate. Pure Ni, Ni-2 at.％W, and Ni-5at.％W alloy substrates were prepared by plasma arc melting, cold rolling, and the recrystallization heat treatment at various temperature (700- 130$0^{\circ}C$). It was observed that Ni-W alloy substrates had stronger cube texture and maintained it at higher annealing temperature, compared to pure Ni substrate : The full-width at half- maximums of in-plane texture was 13.40$^{\circ}$ for Ni substrate and 4.42$^{\circ}$-5.57$^{\circ}$ for Ni-W substrate annealed at 100$0^{\circ}C$. In addition, it was observed that the Ni-W substrate had smaller grain size, shallower boundary depth, and higher hardness, compared to those of pure Ni substrate.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.178-179
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• 2014

In this study, $Ni-W-Si_3N_4$ alloy composite coatings were prepared by pulse electrodeposition method using nickel sulfate bath with different contents of tungsten source, $Na_2WO_4.2H_2O$, and dispersed $Si_3N_4$ nano particles. The structure and microstructure ofcoatings was separately analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results indicated that nano $Si_3N_4$ and W content in alloy had remarkable effect on microstructure, microhardness and scratch resistant properties. Tungsten content in Ni-W and $Ni-W-Si_3N_4$ alloy ranged from 7 to 14 at.%. Scratch test results suggest that as compared to Ni-W only, $Ni-W-Si_3N_4$ prepared from Ni/W molar ratio of 1:1.5 dispersed with 20 g/L $Si_3N_4$ has shown the best result among different samples.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.171-172
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• 2015

$Ni-W-Si_3N_4$ alloy composite coatings were prepared by pulse electro-deposition method using nickel sulfate bath with different contents of tungsten source, $Na_2WO_4.2H_2O$, and dispersed $Si_3N_4$ nano-particles. The structure and micro-structure of coatings was separately analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results indicated that nano $Si_3N_4$ and W content in alloy had remarkable effect on micro-structure, micro-hardness and scratch resistant properties. Tungsten content in Ni-W and $Ni-W-Si_3N_4$ alloy ranged from 7 to 14 at.%. Scratch test results suggest that as compared to Ni-W only, $Ni-W-Si_3N_4$ prepared from Ni/W molar ratio of 1:1.5 dispersed with 20 g/L $Si_3N_4$ has shown the best result among different samples.

• Journal of Powder Materials
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• v.14 no.1 s.60
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• pp.13-18
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• 2007

The mother Ni-W (1-5 wt.%) alloy billets for coated conductor substrate were fabricated by powder metallurgy process. The tensile test results for the sintered Ni-W rods showed the increase of mechanical strength and decrease of ductility with increasing W content due to the solid solution hardening. All the fracture surfaces of the tested specimens showed the typical ductile fracture mode of dimple rupture due to the local necking. The Ni-W alloy billets were made into tape by cold rolling. After the appropriate heat treatment for recrystallization, the brass texture formed by the cold rolling was converted to the complete cube texture. The in-plane and out of plane texture of the tapes estimated by x-ray pole figure were smaller than 9 degree and 7 degree, respectively. The effect of the W addition on the texture development seems not to be significant.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.16-20
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• 2002

In this study, the 95W heavy alloys of 3/7, 5/5 and 7/3 of Ni/Fe ratio were sintered at the temperature range between 1420 and $1480^{\circ}C$ for 1h and their microstructures were discussed for an effect of the ${\mu}$-phase $(Fe_7W_6)$ on the microstructure. The ${\mu}$-phase was observed in the only 95W-1.5Ni-3.5Fe alloy of 3/7 and it is thought to be formed and grown from the surface of the W particle. The W particle was surrounded with the ${\mu}$-phase and there were only the W particles and this phase without Ni-Fe-W matrix at the most part. The ${\mu}$-phase changed the interphase structure in the alloy and the grain growth of the W was suppressed because of interrupting the solution-reprecipitation of the W. The W content in the matrix was considered to be lowered due to the interruption of the solution-reprecipitation and the formation of the ${\mu}$-phase in the .

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.56-56
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• 2001

Ni-W alloy deposit is one of the best alternatives to hard chromium plating because of its good mechanical properties (high hardness, high strength, and good wear resistance). Ni-W alloy is deposited from weakly acidic or alkaline electrolytic bath with nickel sulfate, sodium tungstate or APT, and some kinds of organic hydroxy-acid complex and ammonia salts. W content of the deposit can be changed from 0 to 5Owt% and the coating with high W content is more attracted. But, meanwhile, the deposited layers are always found high internal stress, which cause them to become brittle and to bond insufficiently with the substrate. On the second hand, as the W content is incresed, the current efficiency reduced, which results in large quantities of hydrogen evolution and then produces bubbles on surface and pitting appearance In this paper, the influence of some additives on Ni-W alloy electroplating was investigated by means of compositional analysis and SEM. The initial results showed that 2-butyne-1,4-diol was the best brightener for Ni-W plating process. It could brighten and level deposit, but decreased the cathodic current efficiency. Its optimum concentration range is from O.lgjL to 0.5gjL. Besides, three kinds of additives including 2-butyne-1,4-diol were examined with Dagguchi method.