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2018 Vol. 23, No. 5
Published: 2018-10-20
Theoretical Research
445
Failure modes of AlTiN coated alloys during scratch test and the related mechanism by finite element analysis
ZHANG Huadong, ZHANG Li, CHEN Yi, LUO Guokai, XIAO Qiaoping, ZHONG Zhiqiang
To explore the synergistic effect of the hard phase and the ductile binder phase in cemented carbide substrates to the coating, WC-10Co-0.65Cr
3
C
2
-0.35VC (10Co) with hard phase + binder phase structure, WC-6Mo
2
C-0.68Cr
3
C
2
- 0.37VC (bWC) and 85.1Co-9.2W-4.7Cr
3
C
2
-1.0VC (CoW) alloys were prepared. Al
0.55
Ti
0.45
N coating around 5 μm in thickness was deposited by direct current magnetron sputtering technology. The failure modes of AlTiN coated alloys during scratch test were determined by the magnitude of critical loads
L
C1
and
L
C2
and the difference value between
L
C1
and
L
C2
.
L
C1
and
L
C2
are the characterization parameters of the cohesive failure resistance of the film and the adhesion strength between the film and the substrate, respectively
.
The related failure mechanism was investigated by finite element analysis of the stress distribution in the coating during scratch test. Further, the effects of the WC grain size and the cobalt content in the cemented carbide substrates on the stress distribution in the coating during scratch test were also investigated. The results show that the coated alloy with ductile CoW substrate has the lowest value of
L
C1
and
L
C2
. The coated alloy with hard bWC substrate has the highest
L
C2
and the highest difference value between
L
C1
and
L
C2
. The coated 10Co alloy has the highest
L
C1
and the lowest
L
C1
and
L
C2
difference. The young modulus ratio of the film and the substrate and the hardness of substrate are the key factors affecting
L
C1
and
L
C2
. Decreasing the grain size and choosing moderate cobalt content in cemented carbide substrate facilitate the synchronous improvement of
L
C1
and
L
C2
.
2018 Vol. 23 (5): 445-453 [
Abstract
] (
424
)
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1443
)
Engineering and Technology
454
Effects of TiC content on property and microstructure of Mo-10W-TiC alloy
XIONG Gang, CHENG Huichao, FAN Jinglian, YAO Songsong, LI Xing
Mo-10W-TiC alloys (mass fraction of TiC are 0.5%~6%) were prepared by powder metallurgy method through adding TiC into Mo-W matrix. The effects of TiC content on microstructure and tensile property of Mo-10W-TiC composites were studied. The results show that TiC particles in the green body interdiffuse with the matrix during of sintering, (Mo,Ti)
x
C
y
and a small amount of (W,Ti)
x
C
y
solid solution are formed in the particles, and forming the second phase particles with unsoluted TiC. At the same time, TiC particles can effectively inhibit the grain growth during sintering, and the grain size decreases with increasing the TiC content. The relative density and tensile strength increase firstly and decrease lately with increasing the TiC content sintered at 1 920 ℃. When the TiC content is 4%, Mo-10W-4TiC alloy exhibits the highest relative density of 99.7% and tensile strength of 497 MPa. The addition of excess TiC leads to the bonding strength between the TiC particles and the matrix decreasing. Tensile fracture morphology of the alloy shows that with the increase of TiC content, the fracture mode of the alloy transforms from simple intergranular fracture into mixed mode of intergranular fracture and transgranular fracture.
2018 Vol. 23 (5): 454-459 [
Abstract
] (
376
)
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733
)
460
Effect of the Cr
3
C
2
additive amount on the microstructure and properties of WC-10Co cemented carbides
TANG Qijia, LI Zhongdian, WANG Yanjie, ZHANG Yong
The WC-10Co cemented carbides with different Cr
3
C
2
additive amount (0-4.0%) were prepared by traditional powder metallurgy. The microstructure of the alloy was analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and energy spectrometer. The magnetic force, cobalt magnetic, density, transverse fracture strength, vickers hardness and fracture toughness of the WC-10Co cemented carbides were tested. The effect of Cr
3
C
2
additive amount on the conventional properties was studied. The effect of Cr
3
C
2
addition on the grain size and grain uniformity of WC was emphatically discussed. The results show that addition of Cr
3
C
2
can effectively refine the grain of WC-Co cemented carbide. With increasing Cr
3
C
2
additive amount, the grain uniformity of WC improves, the cobalt magnetism of the alloy decreases linearly, the alloy density and fracture toughness also decrease, the hardness and the magnetic force increase, and the transverse fracture strength increases first and then decreases. The optimal comprehensive mechanical properties of the alloy with the magnetic force of 19.0 kA/m, density of 14.45 g/cm
3
, hardness (HV
30
) of 1 600, bending strength of 3 920 MPa, fracture toughness of 10.5 MPa∙m
1/2
was obtained when the Cr
3
C
2
additive amount is 0.5%.
2018 Vol. 23 (5): 460-466 [
Abstract
] (
393
)
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1138
)
467
Microstructure and mechanical properties of CCF300-3K carbon fiber and KD-II SiC fiber
HU Guangmin, YANG Fenghao, HE Haoyuan, YI Maozhong
The microstructure and mechanical properties of domestic CCF300-3K carbon fiber and KD-II SiC fiber were characterized. The mechanical properties of fibers were measured by tensile test of monofilament. The surface and tensile fracture morphology and inner structure of fibers were observed by SEM, AFM and TEM. The amorphous phase composition of KD-II SiC fibers were determined by XPS. The crystallinity and crystallite size were analyzed by XRD. Some data references for the preparation and application of the fibers were provided. The results show that, there are a large number of grooves on the surface of CCF300-3K carbon fiber which leads to the increasing of surface roughness; The graphite microcrystals with low crystallinity axially distribute along the fiber, and the space between graphite microcrystals is filled with amorphous carbon; The fracture source of the tensile fracture is the grooves on the fiber surface. The surface of KD-II SiC fiber is smooth and the roughness is too small; The grains of silicon carbide with good crystallinity randomly distribute in the matrix which composed of amorphous SiO
x
C
y
and free carbon; The fracture source of the tensile fracture is the internal hole or inclusion. The Weibull statistical analysis indicate that the tensile strength of CCF300-3K carbon fiber and KD-II SiC fiber are 3.08?0.02 GPa and 2.36?0.03 GPa, shape parameter of
m
value are 6.46 and 9.27, respectively. These shows that they have good structure, high mechanical properties and stability, which are fully meeting the requirements of engineering applications.
2018 Vol. 23 (5): 467-474 [
Abstract
] (
550
)
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(627 KB) (
1927
)
475
Effects of distribution of recrystalline grains on mechanical properties of 316L stainless steel
LU Jiaxin, CHEN Zhakun, FANG Tiehui
Two different distributions of recrystalline grains were obtained on a cold-rolled 316L stainless steel through isochronal annealing (IA) and electromagnetic induction heating (EMIH), respectively. The microstructure and mechanical properties of the alloys after isothermal annealing and electromagnetic induction heating were observed and tested. The effects of recrystallization distribution on the mechanical properties of 316L stainless steel were studied. The results show that, the recrystalline grains are uniformly distributed in the IA sample. While a gradient distribution is obtained in the EMIH sample where the volume fraction and grain size of recrystalline grains are declined with depths increased. There are same volume fraction of recrystalline grains and similar strength-ductility synergy in the IA and EMIH samples. The difference in the distribution of recrystalline grains has no significant effects on the mechanical properties of 316L stainless steel. The tensile ductility of the annealed 316L stainless steel is mainly depended on the network formed by the recrystallization and nanotwins. The deformation ability of the network is insensitive to the distribution of the recrystalline grains. Therefore, the effects of the recrystallization distribution on the mechanical properties are suppressed in 316L stainless steel.
2018 Vol. 23 (5): 475-481 [
Abstract
] (
631
)
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(740 KB) (
1186
)
482
Effects of annealing temperature on the microstructure and friction properties of FeCoCrNiMo
0.1
high-entropy alloy fabricated by canned extruding
TIAN Yanwen, REN Junye, HUANG Qianli, LI Qingxiang, ZHOU Shaoqiang, LIU Yin, WU Hong
A high-entropy alloy bar was prepared by canned extruding using gas-atomization FeCoNiMo
0.1
as raw materials. The extruded bar was annealed at 350, 500 and 650 ℃ for 4 h, respectively. The microstructure and phase composition of the samples were analyzed using scanning electron microscopy (SEM) and X-Ray diffraction (XRD). In addition, the hardness and abrasive resistance of the samples were also tested. The results show that the gas-atomized FeCoCrNiMo
0.1
powder has a high sphericity, the extruded and annealed samples are single-phase FCC structure, the hardness of the samples annealed at different temperatures have no obvious change. The change of microstructure is mainly reflected in the grain size and the type and number of the twins. After annealing at 350 ℃, the number of deformation twins decreases, the wear resistance and compression pressure of the alloy decrease slightly, the grain adhesion appeares at the friction interface and the friction coefficient of the alloy decreases. After annealing at 500 ℃ and 650 ℃, the number of twins increases, the wear resistance and yield strength of the alloy increase, the wear mechanism is mainly adhesive wear, and the friction coefficient increases.
2018 Vol. 23 (5): 482-487 [
Abstract
] (
386
)
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(543 KB) (
814
)
488
Microstructure of Nickel-based superalloys prepared by spark plasma sintering
QIN Zijun, LIU Feng, JIANG Liang
Nickel-base superalloys were sintered by spark plasma sintering (SPS) using the powders of FGH96 fabricated by argon vaporization method as raw material. At the same time, the raw material powder was heat-treated under the same conditions as the SPS process, and the FGH96 superalloy was prepared by hot isostatic pressing (HIP). By analyzing the microstructure and grain size of the alloy at different sintering temperatures or different heat preservation time, the grain orientation and grain size of the alloy fabricated by HIP with heat treatment powder were compared, and the microstructure characteristics of SPS Ni-based superalloy were studied. The results show that the alloy is nearly densified after sintering for 40 min. While the microstructure of the alloy is composed of tiny cellular structure and dendrite crystals when sintered at 1 070 ℃. The carbide precipitates distribute mainly inside the grains with a few on the grain boundaries, which results in almost invisible PPBs. The microstructure of the alloy is composed of equiaxed grains when sintered at 1 170 ℃. The carbide precipitates distribute along the prior particle boundaries, which make quite obvious PPBs. It is indicated that the method of SPS can reduce the PPBs in certain degree, but it had no effect on control the grain size.
2018 Vol. 23 (5): 488-494 [
Abstract
] (
644
)
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(0 KB)
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(719 KB) (
730
)
495
Effects of Ni-coated graphite particles on microstructure and properties of graphite/copper composites
LAI Yuanteng, GAN Xueping, XIAO Zhu, LI Zhiyou, LI Zhou, ZHOU Kechao
Graphite/copper composites with high performance were fabricated by spark plasma sintering (SPS) and Cu coated graphite with Ni pre-coating. The morphologies and microstructures of the composites were characterized by SEM, EDS, TEM and XRD, the effects of nickel content on the physical properties of the composite were investigated. The results show that the Ni coating can improve the interfacial bonding strength between Cu matrix and graphite, and the interface of graphite/Cu composites are composed of copper/(Ni+Ni
3
P) coating interface and graphite/(Ni+Ni
3
P) coating interface. The well dispersion of Ni-coated graphite particles in the copper matrix and net-shaped copper matrix can be obtained. Moreover, the hardness, compressive strength and relative density of graphite/copper composites are improved because of the introduction of Ni coating on graphite, and the physical properties increase with increasing the content of Ni coating. The relative density, hardness, and compressive strength of the composites with 10% Ni are 99.68%, 64.58 HB and 281.04 MPa, respectively.
2018 Vol. 23 (5): 495-502 [
Abstract
] (
489
)
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(791 KB) (
1312
)
503
Effects of oxidation time on microstructure and corrosion resistance of micro-arc oxidation film on aluminum alloy
FANG Lei, MA Yunzhu, LIU Wensheng, LIU Yang, LIU Chao, YAN Huanyuan
Micro-arc oxidation (MAO) films were fabricated on 5052 aluminum alloy by micro-arc oxidation in silicate system (Na
2
SiO
3
+KOH) solution. The morphology, elemental distribution and phase composition of MAO films were analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD).The effects of oxidation time on the film thickness, surface porosity, the maximum hole diameter and the corrosion resistance of the film were analyzed emphatically. The results show that the surface of the micro-arc oxidation film has “volcano deposit” morphology, and the film thickness, surface porosity and pore diameter increase with increasing oxidation time. The film mainly with O and Al elements, is composed of γ-Al
2
O
3
and α-Al
2
O
3
phases, in which the content of γ-Al
2
O
3
phase is higher. The corrosion resistance of MAO treated sample is obviously improved, the corrosion current density is decreased by at least two order of degree magnitude, and the electrochemical impedance modulus |Z| is increased at least two order of degree magnitude. With the oxidation time increasing from 10 min to 50 min, the corrosion resistance of the sample first increases and then decreases. When the oxidation time is 20 min, the sample shows the best corrosion resistance.
2018 Vol. 23 (5): 503-510 [
Abstract
] (
421
)
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(0 KB)
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(641 KB) (
1990
)
511
Effects of substrate temperature on microstructure and property of M2 high-speed steel prepared by selective laser melting
DING Huan, LIU Rutie, XIONG Xiang, XU Jie, CHEN Jie, LIAO Ning
M2 high-speed steels were prepared by selective laser melting (SLM) with the substrate temperature of 100, 150 and 200 ℃ respectively. The effects of substrate temperature on the microstructure and mechanical properties of the samples were studied. The results show that increasing of substrate temperature is beneficial to increase the density and uniformity of M2 high-speed steel. When the substrate temperature is 200 ℃, the microstructure of the SLM sample is more uniform and dense, the solid solution of each element and the content of carbide is high. The direction of the columnar crystals no longer grows only along the Z-axis direction. At the same time, the sample with 200 ℃ substrate temperature has the maximum microhardness of 1 150 HV
0.1
, which is increased by 40% compared with the samples with 100 ℃substrate temperature. With increasing substrate temperature from 100 ℃ to 200 ℃, the tensile strength of M2 high-speed steel at room temperature printed along the Z-axis decreases from 865.23 MPa to 443.85 MPa, due to the decrease of the number of columnar grains in a single direction.
2018 Vol. 23 (5): 511-517 [
Abstract
] (
526
)
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(0 KB)
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(464 KB) (
864
)
518
Preparation and properties of graphene reinforced aluminum matrix composites
WANG Yu, ZHU Chuanping, LEI Ting
Improving the interfacial bonding between aluminum matrix and graphene reinforcement is the key to improve the mechanical properties of the aluminum matrix composites. In this paper, copper-coated graphene reinforced aluminum matrix composites were prepared by powder metallurgy and spark plasma sintering (SPS). The effects of different amounts of copper-coated graphene on the mechanical properties and corrosion resistance of aluminum matrix composites were studied. The results show that through the pretreatment of graphene and electroless plating process, the copper coating on graphene surface with uniform size, uniform distribution, complete film and good bonding strength can be obtained. Copper-coated graphene as reinforced phase can improve the wettability and interface bonding strength between graphene and aluminum matrix. When the content of graphene in the composite reaches 0.2%, the composites exhibit the best performance, the density reaches 99.63%, the hardness, tensile strength and bending strength are 60.13 HV, 152.88 MPa and 659.47 MPa, respectively, which increased by 48.95%, 149.48% and 470.08% respectively as compared to pure aluminum. However, the composite materials show decreased corrosion resistance due to the galvanic corrosion between graphene carbon and the aluminum matrix.
2018 Vol. 23 (5): 518-526 [
Abstract
] (
905
)
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(0 KB)
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(608 KB) (
1461
)
527
Bonding and anti-oxidation properties of cermet composite coatings with Ni on surface of nickel-based superalloy for aviation engines
GAO Bo, ZENG Fanhao, GU Yi, LI Yi
In order to make the nickel alloy used in aerospace engine work safely and efficiently under the conditions of high temperature, high pressure and oxygen enrichment. A new Ni/cermet coating containing B
2
O
3
-A1
2
O
3
- BaO-CeO
2
-ZrO
2
(Ni/BACZ) were prepared on GH4586 nickel-based alloy by slurry method. The surface and cross section morphologies and the phase composition of the coating were analyzed by SEM and XRD respectively. The properties of coating were analyzed by the stretching test, oxidation test and thermal shock experiment. The results show that the structure of Ni/BACZ coating is compact and solid with the matrix, and the main phases are Ni, Al
2
O
3
and CeBO
3
. The coating is firmly combined with the matrix, and the tensile strength is more than 55 MPa. Furthermore, the oxidation resistance of GH4586 nickel-base alloy with cermet coating is improved 7 times than that of the uncoated alloy at 900 ℃. Ni can reduce the coating cracks produced by the high temperature thermal stress, improve the toughness of the coating so that it has a great thermal shock resistance.
2018 Vol. 23 (5): 527-533 [
Abstract
] (
363
)
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(0 KB)
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(490 KB) (
661
)
534
Preparation and mechanical property of powder metallurgy Ti-3Al-5Mo-4.5V (TC16) alloy
XIANG Zeyang, XU Rongjun, LIU Bin, LIU Yong
Ti-3Al-5Mo-4.5V (TC16) alloy was prepared by powder metallurgy (PM) process with Ti powder, Al-V alloy powder and Mo powder as raw materials. The microstructure and mechanical properties of the powder metallurgy TC16 alloy were studied. The results show that the powder metallurgy TC16 alloys have a basketweave microstructure composed of α phase and β phase. The powder metallurgy TC16 alloy with the relative density of 93.5%, the tensile strength of 1 062 MPa, the yield strength of 973 MPa and the uniform elongation of 2.3% is obtained, in which the yield strength reachs the level of casted TC16 alloy.
2018 Vol. 23 (5): 534-538 [
Abstract
] (
369
)
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(489 KB) (
738
)
539
Preparation and properties of C/C-SiC composites by high-solid-loading slurry impregnation
YIN Huan, PENG Ke, RAO Fei, YI Maozhong
C/C-SiC composites were prepared by high-solid-loading slurry impregnation and densified by precursor infiltration and pyrolysis (PIP) process. The rheological properties of the slurry, the microstructure, the mechanical properties and the ablative properties of the composites were studied. The results show that a good fluidity and permeability high-solid-loading (40%) SiC slurry can be prepared with 5% ethanol water, when the pH value of slurry is 6 and the mass fraction of PEI is 0.7%. SiC mainly concentrates in the fiber webs between the non-woven layers homogeneously. The bending strength and fracture toughness of C/C-SiC composites are 335.7 MPa and 16.2 MPa·m
1/2
, respectively. C/C-SiC composites have good ablation resistance at 2 000 ℃, and the oxidation product SiO
2
can fill the defects such as pores and cracks to prevent the further oxidation of the materials.
2018 Vol. 23 (5): 539-546 [
Abstract
] (
448
)
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(0 KB)
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(630 KB) (
1443
)
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