• Journal of Powder Materials
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• v.27 no.5
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• pp.414-419
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• 2020

In the present study, we investigated the austenite stability of a sintered Fe-based nanocrystalline alloy. The volume fraction of austenite was measured based on the X-ray diffraction data of sintered Fe-based nanocrystalline alloys, which were prepared by high-energy ball milling and spark plasma sintering. The sintered alloy samples showed a higher volume fraction of austenite at room temperature as compared to the equilibrium volume fraction of austenite obtained using thermodynamic calculations, which resulted from the nanosized crystalline structure of the sintered alloy. It was proved that the austenite stability of the sintered Fe-based alloy increased with a rise in the amount of austenite stabilizing elements such as Mn, Ni, and C; however, it increased more effectively with a decrease in the actual grain size. Furthermore, we proposed a new equation to predict the martensite starting temperature for sintered Fe-based alloys.

• 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 Technologic Dentistry
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• v.37 no.4
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• pp.235-242
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• 2015

Purpose: The aims of this study are compare with microstructure and mechanical properties of Co-Cr-Mo alloys fabricated by powder metallurgy(P/M) process and casting process respectively. Methods: Microstructure and micro-hardness were tested by SEM and Vickers Hardness Tester. The sintered specimen was produced by furnace-coolling after sintering, however the casting specimen were produced thru air-cooling and water-cooling after the casting. For observation of phase transformation during sintering, DSC analyzing was carried out. Results: Mean pore size of sintered Co-Cr-Mo alloy was $4.32{\mu}m$ and that of casting alloy was $1.63{\mu}m$. Hardness of sintered alloy was lower than water-quenched casting alloy. Conclusion: Proper sintering temperature of Co-Cr-Mo alloy was above $1,200^{\circ}C$ and pore size of casting specimen were finer than sintered specimen, but hardness were similar.

• Journal of Technologic Dentistry
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• v.40 no.3
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• pp.125-131
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• 2018

Purpose: Automatic dental prosthesis manufacturing process was accelerated by the spread of dental CAD / CAM system. The CAD / CAM system with milling alloys were needed supplement. So, sintered alloy blocks were introduced. In this study, we want to study sintered alloy block. And to evaluate the alloy block manufacture and alloy properties. Methods: The alloy powders were prepared by high pressure water dispersion method. The sintered alloy blocks were prepared by low temperature pressing method. Their components observation were EDX, and the alloy structure was observed by XRD. Results: Co-Cr alloy powders were observed to have a circle shape with an average diameter of about $100{\mu}m$ and a Ni-Cr alloy powder had a circle shape with an average diameter of about $50{\mu}m$. The Co-Cr alloy block is composed of Co (34.62 wt%), Cr (17.33 wt%), Mo (2.98 wt%), Si (0.36 wt%) and C (44.17 wt%). The Ni-Cr alloy powder was composed of Ni (40.29 wt%), Cr (19.37 wt%), Mo (3.53 wt%), Si (0.52 wt%) and C (33.18 wt%). The peak of the Co and CoCr peaks were observed in the CoCr alloy body by the means of XRD study. Cr2Ni3 of the peak was observed in the Ni-Cr alloy material. Conclusion : As a result, the following conclusions were obtained. 1. Prepared by high-pressure water-law Co-Cr alloy powder has an average diameter $100{\mu}m$, Ni-Cr alloy powder was found to have the form of sphere having an average diameter $50{\mu}m$. 2. Co-Cr alloy and Ni-Cr alloy block produced by low-temperature processing showed a certain ratio. 3. In the XRD study, Co phase appeared in Co-Cr alloy block after sintering. and Cr2Ni3 phase appeared in Ni-Cr alloy block after sintering.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.2
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• pp.102-111
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• 1997

This paper deals with the machinability based on turning of WC-Co allows with the coated and the sintered diamond tools. The main conclusions obtained are as follows. (1) When machining WC-10%Co alloy, the flank wear of sintered diamond tool increases more largely with the increase of cutting speed in comparison with coated diamond tool. The tool wear decreases with the increase of the grain size and nose radius of sintered diamond tool. (2) When machining WC-20%Co alloy, the tool wear and cutting force decrease with the decrease of rake angle. Their exists a certain cutting speed range to exhibit the smallest tool wear in machining the WC-20%Co alloy, and this critical cutting speed becomes higher by 2 times in the case of coated diamond tool compared with sintered diamond tool. (3) The machinability becomes better with the increase of Co content. The effects of cutting speed and feed rate on the roughness of machined surface become smaller with the increase of Co content.

• Journal of Powder Materials
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• v.25 no.4
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• pp.302-308
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• 2018

A lean alloy is defined as a low alloy steel that minimizes the content of the alloying elements, while maintaining the characteristics of the sintered alloy. The purpose of this study is to determine the change in microstructure and mechanical properties due to the addition of silicon or tin in Fe-Mo-P, Fe-Mn-P, and Fe-Mo-Mn-P alloys. Silicon- or tin-added F-Mo-P, Fe-Mn-P, and Fe-Mo-Mn-P master alloys were compacted at 700 MPa and subsequently sintered under a $H_2-N_2$ atmosphere at $1120^{\circ}C$. The sintered density of three alloy systems decreases under the same compacting pressure due to dimensional expansion with increasing Si content. As the diffusion rate in the Fe-P-Mo system is higher than that in the Fe-P-Mn system, the decrease in the sintered density is the largest in the Fe-P-Mn system. The sintered density of Sn added alloys does not change with the increasing Sn content due to the effect of non-dimensional changes. However, the effect of Si addition on the transverse rupture strengthening enhancement is stronger than that of Sn addition in these lean alloys.

• Journal of the Korean Magnetics Society
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• v.10 no.6
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• pp.269-273
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• 2000

Fe-l7Cr-2M(M=Si, Nb, Mo) alloy powder was prepared by plasma electrode rotating atomizer and than the alloy powder was formed and sintered. The particle shape of the Fe-l7Cr-2M(M=Si, Nb, Mo) alloy power is spherical. The saturation magnetization of the sintered Fe-17Cr-2Mo and Fe-l7Cr-2Nb alloy are 155 emu/g. The saturation magnetization of the sintered Fe-l7Cr-2Si alloy is less than that of the sintered Fe-l7Cr-2Mo and Fe-l7Cr-2Nb alloy. The amplitude relative permeability of the sintered Fe-l7Cr-2M(M=Si, Nb, Mo) alloy has the maximum value in the range of 3∼5 Oe applied field at forming pressure 12 ton/cm$^2$, sintering temperature 1200$^{\circ}C$, and frequency 1 kHz. Power loss of the sintered Fe-l7Cr-2Nb alloy is 40 mW/cc at applied field, H$\sub$a/=5 Oe, and frequency, f=1 kHz. The power loss of the sintered Fe-l7Cr-2Nb alloy is a half of that of the sintered Fe-l7Cr-2Si and Fe-l7Cr-2Mo alloy.

• Journal of Powder Materials
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• v.30 no.6
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• pp.470-477
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• 2023

The effects of annealing on the microstructure and mechanical properties of Al-Zn-Mg-Cu-Si alloys fabricated by high-energy ball milling (HEBM) and spark plasma sintering (SPS) were investigated. The HEBM-free sintered alloy primarily contained Mg₂Si, Q-AlCuMgSi, and Si phases. Meanwhile, the HEBM-sintered alloy contains Mg-free Si and θ-Al₂Cu phases due to the formation of MgO, which causes Mg depletion in the Al matrix. Annealing without and with HEBM at 500℃ causes partial dissolution and coarsening of the Q-AlCuMgSi and Mg₂Si phases in the alloy and dissolution of the θ-Al₂Cu phase in the alloy, respectively. In both alloys, a thermally stable α-AlFeSi phase was formed after long-term heat treatment. The grain size of the sintered alloys with and without HEBM increased from 0.5 to 1.0 ㎛ and from 2.9 to 6.3 ㎛, respectively. The hardness of the sintered alloy increases after annealing for 1 h but decreases significantly after 24 h of annealing. Extending the annealing time to 168 h improved the hardness of the alloy without HEBM but had little effect on the alloy with HEBM. The relationship between the microstructural factors and the hardness of the sintered and annealed alloys is discussed.

• The Journal of Advanced Prosthodontics
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• v.10 no.2
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• pp.128-131
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• 2018

PURPOSE. This study aimed to evaluate the marginal discrepancy of full-arch frameworks in implant-supported prostheses fabricated using pre-sintered soft alloy (PSA). MATERIALS AND METHODS. Full-arch metal frameworks were fabricated on the edentulous implant model using casting alloy (CA), fully-sintered hard alloy (FHA), and PSA (n = 4 in each group). To evaluate the misfit of the framework to the abutments, the absolute marginal discrepancy (AMD) values of the frameworks were measured in cross-sectional images that had been drawn as part of the triple-scan protocol. The AMD values were compared among the tested alloy groups using the Kruskal-Wallis test, with a post hoc Mann-Whitney U test (${\alpha}=.05$). RESULTS. The FHA and PSA groups showed lower marginal discrepancies than the CA group (P<.001). However, the FHA group did not differ significantly from the PSA group. CONCLUSION. Soft alloy milling is comparable to hard alloy milling, and it is more precise than casting in terms of the marginal fit of implant-supported, full-arch prostheses.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.301-302
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• 2006

Machinability and machining mechanism were examined in the case where resin impregnation treatment was conducted to the Mo-Co hardening particle dispersed iron-based sintered alloy. As a result, the force required for machining decreased significantly compared with the case where resin impregnation treatment was not conducted. This effect is considered to be attributable to the embrittlement of cutting chips produced by the minimization of the cut material deformation.