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1.
Jun Cheol Oh Sunghak Lee Mikhail G. Golkovski 《Metallurgical and Materials Transactions A》2001,32(12):2995-3005
This study is concerned with the microstructural analysis and improvement of the hardness and wear resistance of Ti-6Al-4V
surface-alloyed materials fabricated by a high-energy electron beam. The mixtures of TiC, TiN, or TiC + TiN powders and CaF2 flux were deposited on a Ti-6Al-4V substrate, and then the electron beam was irradiated on these mixtures. In the specimens
processed with a flux addition, the surface-alloyed layers of 1 mm in thickness were homogeneously formed without defects
and contained a large amount (over 30 vol pct) of precipitates such as TiC, TiN, (Ti
x
Al1−x
)N, and Ti(C
x
N1−x
) in the martensitic or N-rich acicular α-Ti matrix. This microstructural modification, including the formation of hard precipitates and hardened matrices in the surface-alloyed
layers, improved the hardness and wear resistance. Particularly in the surface-alloyed material fabricated by the deposition
of TiN powders, the wear resistance was greatly enhanced to a level 10 times higher than that of the Ti alloy substrate. These
findings suggested that surface alloying using high-energy electron-beam irradiation was economical and useful for the development
of titanium-based surface-alloyed materials with improved hardness and wear resistance. 相似文献
2.
The correlation of microstructure with the hardness and wear resistance of (TiC,SiC)/Ti-6Al-4V surface composites fabricated
by high-energy electron-beam irradiation was investigated in this study. The mixtures of TiC, SiC, or TiC + SiC powders and
CaF2 flux were placed on a Ti-6Al-4V substrate, and then an electron beam was irradiated on these mixtures using an electron-beam
accelerator. The surface composite layers of 1.2 to 2.1 mm in thickness were formed without defects and contained a large
amount (up to 66 vol pct) of precipitates such as TiC and Ti5Si3 in the martensitic matrix. This microstructural modification, including the formation of hard precipitates and a hardened
matrix in the surface composite layer, improved the hardness and wear resistance. Particularly in the surface composite fabricated
with TiC + SiC powders, the wear resistance was greatly enhanced to a level 25 times higher than that of the Ti alloy substrate,
because 66 vol pct of TiC and Ti5Si3 was precipitated homogeneously in the hardened martensitic matrix. These findings suggested that high-energy electron-beam
irradiation was useful for the development of Ti-based surface composites with improved hardness and wear properties. 相似文献
3.
Kwangjun Euh Jongmin Lee Sunghak Lee 《Metallurgical and Materials Transactions A》2001,32(10):2499-2508
The present study is concerned with the fabrication and microstructural analysis of boride/Ti-6Al-4V surface-alloyed materials
using the irradiation of a high-energy electron beam. Mixtures of TiB2 or MoB powders and CaF2 flux were placed on a Ti-6Al-4V alloy substrate and subsequently irradiated using a high-energy electron beam. Specimens
processed with a flux mixing ratio of 40 wt pct showed that the melted region of 1.1 to 1.5 mm in thickness was homogeneously
formed without defects and contained a large amount of titanium borides (TiB). The formation of TiB in the melted region greatly
improved the Vickers hardness, high-temperature Vickers hardness, and wear resistance to levels 2 or 3 three times higher
than the those for the Ti alloy substrate. Also, the addition of MoB powders into the mixtures made possible the fabrication
of surface-alloyed materials with various properties by controlling the kind, size, and volume fraction of TiB and the characteristics
of the matrix. These findings suggested that surface alloying using high-energy electron-beam irradiation was economical and
useful for the development of boride/Ti-6Al-4V surface-alloyed materials with improved properties. 相似文献
4.
This study is concerned with the correlation of microstructure and abrasive and sliding wear resistance of (TiC,SiC)/Ti-6Al-4V
surface composites fabricated by high-energy electron-beam irradiation. The mixtures of TiC, SiC, Ti + SiC, or TiC+SiC powders
and CaF2 flux were deposited on a Ti-6Al-4V substrate, and then an electron beam was irradiated on these mixtures. The surface composite
layers of 1.2 to 2.1 mm in thickness were homogeneously formed without defects and contained a large amount (30 to 66 vol
pct) of hard precipitates such as TiC and Ti5Si3 in the martensitic matrix. This microstructural modification, including the formation of hard precipitates in the surface
composite layer, improved the hardness and abrasive wear resistance. Particularly in the surface composite fabricated with
TiC + SiC powders, the abrasive wear resistance was greatly enhanced to a level 25 times higher than that of the Ti alloy
substrate because of the precipitation of 66 vol pct of TiC and Ti5Si3 in the hardened martensitic matrix. During the sliding wear process, hard and coarse TiC and Ti5Si3 precipitates fell off from the matrix, and their wear debris worked as abrasive particles, thereby reducing the sliding wear
resistance. On the other hand, needle-shaped Ti5Si3 particles, which did not play a significant role in enhancing abrasive wear resistance, lowered the friction coefficient
and, accordingly, decelerated the sliding wear, because they played more of the role of solid lubricants than as abrasive
particles after they fell off from the matrix. These findings indicated that high-energy electron-beam irradiation was useful
for the development of Ti-based surface composites with improved abrasive and sliding wear resistance, although the abrasive
and sliding-wear data should be interpreted by different wear mechanisms. 相似文献
5.
Correlation of microstructure with hardness and wear resistance of VC/carbon steel surface-alloyed materials fabricated by
high-energy electron-beam irradiation was investigated. The mixtures of VC powders and flux (50 pct MgO-50 pct CaO or CaF2) were deposited on a plain carbon steel substrate, and subsequently irradiated using a high-energy electron beam. The surface-alloyed
layers of 1.2 to 3 mm in thickness were homogeneously formed without defects, and contained a large amount (about 10 vol pct)
of VC precipitates in the bainitic or martensitic matrix. This microstructural modification including the formation of hard
precipitates and hardened matrix in the surface-alloyed layers improved hardness and wear resistance. Particularly in the
surface-alloyed material fabricated with the lower input energy density, the wear resistance was greatly enhanced over the
steel substrate because of the increased size and volume fraction of VC particles, although the thickness of the surface-alloyed
layer decreased. Microstructural modifications including melting, solidification, precipitation, and phase transformation
of the surface-alloyed layer were also predicted from a thermal transfer modeling and a Fe-V-C ternary phase diagram. The
predicted results were found consistent with those data from actual electron-beam irradiation and microstructural analysis. 相似文献
6.
Jun Cheol Oh Chang Sup Lee Sunghak Lee 《Metallurgical and Materials Transactions A》2002,33(10):3173-3185
Correlation of microstructure with the hardness, wear resistance, and fracture toughness of two-layered VC/Ti-6Al-4V surface
composites fabricated by high-energy electron-beam irradiation was investigated in this study. A mixture of VC powders and
CaF2 flux was deposited on a Ti-6Al-4V substrate, and then an electron beam was irradiated on these powder mixtures to fabricate
an one-layered surface composite. A two-layered surface composite was fabricated by irradiating an electron-beam again onto
the powder mixture deposited on the one-layered surface composite. The composite layers of 1.2 to 1.5 mm in thickness were
homogeneously formed without defects and contained a large amount (25 to 40 vol pct) of carbides in the martensitic or β-Ti matrix. This microstructural modification, including the formation of hard carbides and hardened matrix, improved the
hardness and wear resistance. Particularly in the two-layered surface composite containing more carbides, the wear resistance
was greatly enhanced to a level 7 times higher than that of the Ti-6Al-4V substrate. In-situ observation of the fracture process showed that microcracks were initiated at carbides and propagated along these microcracked
carbides and that shear bands were formed in the matrix between these microcracks. In the two-layered surface composite, numerous
microcracks were initiated at many carbides and then rapidly propagated along them, thereby lowering the fracture toughness. 相似文献
7.
Eunsub Yun Yong Chan Kim Sunghak Lee Nack J. Kim 《Metallurgical and Materials Transactions A》2004,35(3):1029-1038
Stainless-steel-based surface composites reinforced with TiC and SiC carbides were fabricated by high-energy electron beam
irradiation. Four types of powder/flux mixtures, i.e., TiC, (Ti + C), SiC, and (Ti + SiC) powders with 40 wt. pct of CaF2 flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with an electron beam. TiC
agglomerates and pores were found in the surface composite layer fabricated with TiC powders because of insufficient melting
of TiC powders. In the composite layer fabricated with Ti and C powders having lower melting points than TiC powders, a number
of primary TiC carbides were precipitated while very few TiC agglomerates or pores were formed. This indicated that more effective
TiC precipitation was obtained from the melting of Ti and C powders than of TiC powders. A large amount of precipitates such
as TiC and Cr7C3 improved the hardness, high-temperature hardness, and wear resistance of the surface composite layer two to three times greater
than that of the stainless steel substrate. In particular, the surface composite fabricated with SiC powders had the highest
volume fraction of Cr7C3 distributed along solidification cell boundaries, and thus showed the best hardness, high-temperature hardness, and wear
resistance. 相似文献
8.
Eunsub Yun Yong Chan Kim Sunghak Lee Nack J. Kim 《Metallurgical and Materials Transactions A》2004,35(13):1029-1038
Stainless-steel-based surface composites reinforced with TiC and SiC carbides were fabricated by high-energy electron beam
irradiation. Four types of powder/flux mixtures, i.e., TiC, (Ti+C), SiC, and (Ti+SiC) powders with 40 wt. pct of CaF2 flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with an electron beam. TiC
agglomerates and pores were found in the surface composite layer fabricated with TiC powders because of insufficient melting
of TiC powders. In the composite layer fabricated with Ti and C powders having lower melting points than TiC powders, a number
of primary TiC carbides were precipitated while very few TiC agglomerates or pores were formed. This indicated that more effective
TiC precipitation was obtained from the melting of Ti and C powders than of TiC powders. A large amount of precipitates such
as TiC and Cr7C3 improved the hardness, high-temperature hardness, and wear resistance of the surface composite layer two to three times greater
than that of the stainless steel substrate. In particular, the surface composite fabricated with SiC powders had the highest
volume fraction of Cr7C3 distributed along solidification cell boundaries, and thus showed the best hardness, high-temperature hardness, and wear
resistance. 相似文献
9.
In the present work, TiC–TiB–TiB2 diffusion-layer-coated B4C composite powders were synthesised via a powder immersion method using Ti and B4C powders as reactants. The phase compositions and microstructure of the treated powders were characterised by employing X-ray diffraction and scanning electron microscopy. No significant reaction between B4C and Ti could be detected at 800°C. After treatment at 900°C, the products generated were composed of TiC and TiB. After treatment at 1000°C, the products generated were primarily composed of TiC and TiB, with a small amount of TiB2. The composition and proportions of the produced phases varied with process temperatures and the composition of the initial powders used. Powder mixtures with a Ti/B4C molar ratio of 3.5:1 and treated at 1000°C for 14?h were more suitable for synthesis of TiC–TiB–TiB2-coated B4C composite powders. 相似文献
10.
11.
Correlation of microstructure with hardness and wear resistance of (CrB,MoB)/carbon steel surface composites fabricated by
high-energy electron beam irradiation was investigated in this study. Three kinds of powder mixtures, i.e., 50CrB-50MgF2(flux), 50MoB-50MgF2, and 25CrB-25MoB-50MgF2 (wt pct), were placed on a plain carbon steel substrate, which was then irradiated with the electron beam. In the specimens
fabricated with flux powders, the surface composite layer of 0.8 to 1.3 mm in thickness was successfully formed without defects,
and contained a large amount (up to 48 vol pct) of Cr1.65Fe0.35B0.9 or Mo2FeB2 in the martensitic matrix. The hardness and wear resistance of the surface composite layer were directly influenced by the
hard borides, and thus were about 3 to 7 times greater than those of the steel substrate. Particularly, in the surface composite
fabricated with CrB and MoB powders, the hardness of eutectic solidification cells and martensitic matrix was very high, and
borides formed a network structure along cells, thereby leading to the best hardness and wear resistance. These findings suggested
that the high-energy electron beam irradiation was useful for the development of surface composites with improved hardness
and wear resistance. 相似文献
12.
Microstructural analysis of vanadium carbide/steel surface-alloyed materials fabricated by high-energy electron-beam irradiation 总被引:1,自引:0,他引:1
Kwangjun Euh Sunghak Lee Seonghun Choo 《Metallurgical and Materials Transactions A》2000,31(11):2849-2855
This study is concerned with the microstructural analysis of vanadium carbide (VC)/steel surface-alloyed materials fabricated
by high-energy electron-beam irradiation. The mixtures of VC powders and MgO-CaO flux were deposited on a plain carbon steel
substrate, and then electron beam was irradiated on these mixtures using an electron-beam accelerator. Microstructures of
the irradiated surface regions were examined by optical microscopy, scanning electron microscopy, and transmission electron
microscopy. Residual pores were found in the specimen processed without flux, but hardly found in the specimens processed
with a considerable addition of flux. As a result of irradiation, vanadium content was homogeneously maintained throughout
the melted region, and fine vanadium carbides were formed in the melted region. These microstructural modification including
the formation of vanadium carbides greatly improved hardness, especially high-temperature hardness up to 500 °C. 相似文献
13.
稀土元素的添加对原位生成的Ti-TiC-TiB复合材料抗磨损性能的影响 总被引:1,自引:1,他引:1
采用Ti 6Al 4V 5B4C和Ti 6Al 4V 5B4C 1Nd 两种成分的原始粉末, 反应热压后原位生成了Ti TiC TiB复合材料。经过X射线检测, 证明了试验中原位生成反应5Ti+B4C 4TiB+TiC的进行。采用摩擦磨损试验机检测了两种材料的抗磨损性能。通过扫描电子显微镜和电子探针分析了材料的磨损表面。结果表明, 添加稀土元素能提高材料的硬度, 韧性和抗磨损性能。 相似文献
14.
Kwangjun Euh Sunghak Lee Keesam Shin 《Metallurgical and Materials Transactions A》1999,30(12):3143-3151
The processing and the microstructural analysis of TiB2/carbon steel surface-alloyed materials using the irradiation of a high-energy electron beam were investigated in this study.
The mixtures of TiB2 powders and flux were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these mixtures
using an electron beam accelerator. The microstructure of the irradiated surface layer was composed of a melted region, an
interfacial region, a coarse-grained heat-affected zone (HAZ), and a fine-grained HAZ. A few residual micropores were found
in the melted region of the specimen processed without flux because of irregular thermal transfer, but their number was decreased
in the specimens processed with a considerable amount of flux. As a result of irradiation, the Ti content was homogeneously
maintained throughout the melted region, whose hardness was greatly improved. This was associated with the microstructural
modification including the segregation of Ti and B along solidification cell boundaries and the formation of fine Ti(C, N)
particles. The proper flux mix ratio was 15 to 30 pct to obtain excellent surface alloying and a homogeneous microstructure. 相似文献
15.
Seong-Hun Choo Sunghak Lee Soon-Ju Kwon 《Metallurgical and Materials Transactions A》1999,30(12):3131-3141
Surface composites reinforced with TiC particulates were fabricated by high-energy electron-beam irradiation. In order to
investigate the effects of flux addition on the TiC dispersion in surface composite layers, four kinds of powder mixtures
were made by mixing TiC with 5, 10, 20, and 40 wt pct of the flux components (MgO-CaO). To fabricate TiC-reinforced surface
composites, the TiC-flux mixtures were deposited evenly on a plain carbon steel substrate, which was subjected to electron-beam
irradiation. Microstructural analysis was conducted using X-ray diffraction and Mossbauer spectroscopy as well as optical
and scanning electron microscopy. The microstructure of the surface composites was composed of a melted region, an interfacial
region, a coarse-grained heat-affected zone (HAZ), a fine-grained HAZ, and an unaltered original substrate region. TiC agglomerates
and residual pores were found in the melted region of materials processed without flux, but the number of agglomerates and
pores was significantly decreased in materials processed with a considerable amount of flux. As a result of irradiation, TiC
particles were homogeneously distributed throughout the melted region of 2.5 mm in thickness, whose hardness was greatly increased.
The optimum flux amount, which resulted in surface composites containing homogeneously dispersed TiC particles, was found
to be in the range of 10 to 20 pct to obtain excellent surface composites. 相似文献
16.
Duk-Hyun Nam Kyuhong Lee Sunghak Lee 《Metallurgical and Materials Transactions A》2007,38(6):1193-1201
17.
Synthesis and Characterization of Ti/(TiB + TiC) Hybrid in-situ Composites by Spark Plasma Sintering
Since Ti alloys exhibit inferior wear resistance and suffer considerable loss in mechanical strength at high temperature, it is aimed at synthesis an in-situ Ti/(TiB + TiC) hybrid composite. In order to synthesis Ti/(TiB + TiC) in-situ composite, B4C particulate was mixed with titanium powder and sintered at 1400 °C at different time intervals by spark plasma sintering. Sintering parameters were optimized according to the complete in-situ reactions. Density of the sintered compacts was measured by Archimedes principle. Energy dispersive spectroscope and optical microscope observations of the sintered samples revealed that with increasing sintering time TiB and TiC particulates were gradually transforming into needle like structure and near equiaxed structure, respectively. 相似文献
18.
Jeonghyeon Do Changwoo Jeon Duk-Hyun Nam Choongnyun Paul Kim Young Buem Song Sunghak Lee 《Metallurgical and Materials Transactions A》2011,42(5):1191-1204
In this study, multilayered, Zr-based amorphous surface composites were fabricated by high-energy electron-beam irradiation;
the correlation of their microstructure, hardness, compressive properties, and fracture properties with ballistic performance
was investigated. The mixture of Zr-based amorphous powders and LiF + MgF2 flux powders was deposited on a pure Ti substrate or a plain carbon steel substrate, and then an electron beam was irradiated
on this powder mixture to fabricate a one-layered surface composite. The multilayered surface composite was fabricated by
an irradiating electron beam several times again onto the powder mixture deposited on the one-layered surface composite. The
microstructural analysis results indicated that a small amount of fine crystalline particles was distributed homogeneously
in the surface composite layer. Because the surface composite layers absorbed the ballistic impact energy by forming many
cracks or microcracks, the surface composite plates were not perforated during the ballistic impact test. On the one hand,
in the surface composite without containing ductile β phases, the composite layer was cracked completely and fallen off from the substrate. On the other hand, a small amount of
fragmentation was found in the impacted area of the composite containing β phases because it had the sufficient hardness and fracture toughness simultaneously for effectively blocking the traveling
of a projectile, thereby improving ballistic performance. 相似文献
19.
Kyuhong Lee Duk-Hyun Nam Sunghak Lee Choongnyun Paul Kim 《Metallurgical and Materials Transactions A》2006,37(5):1485-1494
In this study, surface composites were fabricated with Fe-based metamoprhic powders by high-energy electron beam irradiation,
and the correlation of their microstructure with hardness and wear resistance was investigated. Fe-based metamorphic powders
were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these powders without flux to fabricate
a one-layered surface composite. A two-layered surface composite was also fabricated by irradiating electron beam again onto
the powders deposited on the one-layered surface composite. The composite layers of 1.3∼1.9 mm in thickness were homogeneously
formed without defects and contained a large amount (up to 48 vol pct) of hard and fine Cr2B crystalline phases in the Cr0.19Fe0.7Ni0.11 matrix. Since the hardness and wear resistance of the surface composite layers were directly influenced by hard Cr2B phases, they were two to three times greater than those of the steel substrate. In particular, the two-layered surface composite
showed a high hardness of ∼300 VHN even at 750 °C, as well as at room temperature, because Cr2B phases and the Cr0.19Fe0.7Ni0.11 matrix were hard and thermally stable. 相似文献
20.