• Journal of the Korean Electrochemical Society
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• v.12 no.3
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• pp.258-262
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• 2009

The composition and semiconducting properties of the passive films formed on Ni- (15, 30)Cr-5Mo alloys in pH 8.5 buffer solution were examined. The depth concentration profile of passive films formed on Ni-(15, 30)Cr-5Mo in pH 8.5 buffer solution showed that Mo enhances the enrichment of Cr. The Mott-Schottky plot for the passive film on Ni-(15, 30)Cr- 5Mo closely resembled that for the film on Cr, whereas those for the less Cr-enriched film on Mo-free alloys showed similar behavior to that for the film on Ni. The acceptor density was reduced by increasing Cr content in Ni-(15, 30)Cr-(0, 5)Mo alloys, but addition of Mo considerably increased the acceptor density.

• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.139-148
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• 2018

In this study, surface analysis of Ni-Cr and Co-Cr alloys with addition of Ti and Mo for dental CAD/CAM use has been researched experimentally. The surface characteristics of the alloys were examined by Vickers hardness test, bonding strength test, surface roughness test, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction spectroscopy. The shrinkage of the sintered Ni-Cr alloy alloy was slightly larger than that of Ni-Cr-Ti alloy, and larger than Co-Cr alloy. Also, the addition of Mo showed a tendency to decrease shrinkage somewhat. From the result of XRD analysis, NiCr, $Ni_3Cr$ and $Ni_3Ti$ were observed in the sintered Ni-13Cr-xTi and Ni-13Cr-xMo alloys. In addition, ${\sigma}-CrCo$, $Co_2Mo_3$ and $TiCo_2$ were formed in the sintered Co-Cr-xTi and Co-Cr-xMo alloys. Surface hardness of Ti and Mo added alloy was higher than those of Ni-Cr and Co-Cr alloy. The bond strength between sintered alloy and porcelain was $16.1kgf/mm^2$ for Ni-13Cr alloy, $17.8kgf/mm^2$ for Ni-13Cr-5Ti alloy, and $8.2kgf/mm^2$ for Ni-13Cr-10Ti alloy, respectively.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_2
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• pp.435-441
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• 2021

This research was performed to study the effect of the Ni + Mo addition on the fatigue properties in 12Cr steel. After heat treatment of 12Cr steel and 12Cr-Ni-Mo steel, tensile tests, impact tests, hardness tests, and rotary bending fatigue tests were performed, respectively. The fatigue fracture surface was observed and analyzed using SEM and EDS. The fatigue limit of 12Cr steel was 554 MPa, which was 49 MPa higher than 505 MPa of 12Cr-Ni-Mo steel. Striations, which are the shape of the typical fatigue fracture surface, were observed at the fracture surface near the starting point of fatigue fracture in the 12Cr steel and 12Cr-Ni-Mo steel. However, unlike the case of 12Cr steel, 12Cr-Ni-Mo steel also had a mixed fracture surface with the fatigue and the ductile fracture surface. When brittle non-metallic inclusions exist near the starting point of fatigue failure, the crack propagation was further promoted and the fatigue life was drastically reduced.

• Korean Journal of Metals and Materials
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• v.48 no.3
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• pp.194-202
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• 2010

Application of a stronger and more durable material for reactor pressure vessels (RPVs) might be an effective way to insure the integrity and increase the efficiency of nuclear power plants. A series of research projects to apply the SA508 Gr.4 steel in ASME code to RPVs are in progress because of its excellent strength and durability compared to commercial RPV steel (SA508 Gr.3 steel). In this study, the microstructural characteristics and mechanical properties of SA508 Gr.3 Mn-Mo-Ni low alloy steel and SA508 Gr.4N Ni-Mo-Cr low alloy steel were investigated. The differences in the stable phases between these two low alloy steels were evaluated by means of a thermodynamic calculation using ThermoCalc. They were then compared to microstructural features and correlated with mechanical properties. Mn-Mo-Ni low alloy steel shows the upper bainite structure that has coarse cementite in the lath boundaries. However, Ni-Mo-Cr low alloy steel shows the mixture of lower bainite and tempered martensite structure that homogeneously precipitates the small carbides such as $M_{23}C_6$ and $M_7C_3$ due to an increase of hardenability and Cr addition. In the mechanical properties, Ni-Mo-Cr low alloy steel has higher strength and toughness than Mn-Mo-Ni low alloy steel. Ni and Cr additions increase the strength by solid solution hardening. In addition, microstructural changes from upper bainite to tempered martensite improve the strength of the low alloy steel by grain refining effect, and the changes in the precipitation behavior by Cr addition improve the ductile-brittle transition behavior along with a toughening effect of Ni addition.

• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.260-264
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• 2016

In this study, fractured surface morphology and mechanical properties of Ni-Cr-Mo alloys with various contents of Mo for dental material use have been evaluated by mechanical test. The alloys used were Ni-13Cr-xMo alloys with Mo contents of 4, 6, 8, and 10 wt.%, prepared by using a vacuum arc-melting furnace. Ni-13Cr-xMo alloys were used for mechanical test without heat treatment. The phase and microstructure of alloys using an X-ray diffraction (XRD) and optical microscopy (OM) were evaluated. To examine the mechanical properties of alloys according to microstructure changes, the tensile test and the hardness test were carried out using tensile tester. To understand the mechanism of Mo addition to Ni-Cr alloy on mechanical property, the morphology and fractured surfaces of alloys were investigated by field-emission scanning electron microscope (FE-SEM). As a result, 79Ni-13Cr-8Mo alloy was verified that the tensile strength and the hardness were better than others. Varying Mo content, the changes of microstructures of alloys were identified by OM and SEM and that of 79Ni-13Cr-8Mo alloy was proved fabricated well. Microstructures of alloys were changed depending on Mo content ratio. It has been observed that 8% alloy had the most suitable mechanical property for dental alloy.

• Korean Journal of Metals and Materials
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• v.47 no.9
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• pp.533-541
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• 2009

Materials used for a reactor pressure vessel(RPV) are required high strength and toughness, which determine the safety margin and life of a reactor. Ni-Mo-Cr low alloy steel shows better mechanical properties than existing RPV steels due to higher Ni and Cr contents compared to the existing RPV steels. The present study focuses on effects of Ni, Cr contents on the cleavage fracture toughness of Ni-Mo-Cr low alloy steels in the transition temperature region. The fracture toughness was characterized by a 3-point bend test of precracked Charpy V-notch(PCVN) specimens based on ASTM E1921-08. The test results indicated that the fracture toughness was considerably improved with an increase of Ni and Cr contents. Especially, control of Cr content was more effective in improving fracture toughness than manipulating Ni content, though Charpy impact toughness was changed more extensively by adjusting Ni content. These differences between changes in the fracture toughness and that in the impact toughness were derived from microstructural features, such as martensite lath size and carbide precipitation behavior.

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.845-849
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• 2002

Alloys of $Fe_3$Al, $Fe_3$Al-6Cr, $Fe_3$Al-4Cr-1Mo, $Ni_3$Al, and $Ni_3$Al-2.8Cr were oxidized at $1000^{\circ}C$ in air, and the oxide scales formed were studied using XRD. SEM, EPMA, and TEM. The oxide scales that formed on $Fe_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$ containing a small amount of dissolved Fe and Cr ions, whereas those that formed on $Ni_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$, together with a small amount of $NiAl_2$$O_4$, NiO and dissolved Cr ions. For the entire alloys tested, nonadherent oxide scales formed, and voids were inevitably existed at the scale-matrix interface.

• Analytical Science and Technology
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• v.16 no.1
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• pp.82-89
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• 2003

Isotope dilution mass spectrometry (IDMS) was applied to the determination of Ni, Cr, Mo in low alloy steel reference materials. The Mo isotope ratio measurement was performed by dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP/MS) using ammonia as a reaction cell gas. In the case of Ni and Cr measurement, all data were obtained at medium resolution mode (m/${\Delta}m=3000$) of double focusing sector field high resolution inductively coupled plasma mass spectrometry (HR-ICP/MS). For the method validation of the technique was assessed using the certified reference materials such as NIST SRM 361, NIST SRM 362, NIST SRM 363, NIST SRM 364, NIST SRM 36b. This method was applied to the determination of Ni, Cr and Mo in low alloy steel sample (CCQM-P25) provided by NMIJ for international comparison study.

• Journal of Korea Foundry Society
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• v.27 no.3
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• pp.120-125
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• 2007

The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.

• Journal of the Korean institute of surface engineering
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• v.50 no.3
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• pp.164-169
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• 2017

Ni-Cr-X ternary interlayers were investigated to improve the adhesion of Cu/Ni-Cr/Polyimide flexible copper clad laminates. The ternary compounds are sputtered Ni-Cr-X films (where X is one of Nb, V, Mo, or Ti), and the effect of third elements on the adhesion was evaluated and investigated chemically and mechanically. The feel strength was higher in the order of Ni-Cr-Nb > Ni-Cr-V > Ni-Cr > Ni-Cr-Mo > Ni-Cr-Ti. Nb, which has a comparable standard electrode potential to Cr, increased the adhesion, while Ti, with a low standard electrode potential, degraded the adhesion. The Ni-Cr-Nb interlayer was amorphous, while Ni-Cr-Ti was partially crystalline. The similar morphology structure of the Ni-Cr-Nb interlayer with polyimide resulted in a better adhesion.