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2019 Vol. 24, No. 2
Published: 2019-04-15
Engineering and Technology
95
Effect of multiple laser cladding processes on microstructure and properties of Fe-based alloy coatings
FU Li, HUANG Huanhuan, CHEN Xiaoming, LIU Wei, ZHAO Jian, ZHANG Lei, ZHOU Xialiang
A FeCoCrNiAlTiSi Fe-based alloy coating was prepared on the substrate Q235 steel surface by repetitive preplaced powder type laser cladding technology. XRD, SEM, microhardness, and electrochemical test, etc. were used to measure and analyze the phase composition, morphology, microhardness and electrochemical properties of the coating. The results show that the composition of the coating is basically stable as Fe
50
Co
10
Cr
10
Ni
10
Al
1
Ti
1
Si
10
phase after repeated cladding. Its main structure transforms from BCC to FCC and with enriched (Al,Ni) phase. In addition, the microhardness value is higher than that of the base material, approaching closing to 700 HV, and the over-passivation potential extends to 0.212 V and corrosion current density 1.69×10
-6
A/cm
2
.
2019 Vol. 24 (2): 95-99 [
Abstract
] (
344
)
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722
)
100
Microstructure and properties of ultrafine-grained WC-Al
x
CrFeCoNi composites prepared by hot pressing
ZHOU Panlong, XIAO Daihong, ZHOU Pengfei, YU Yongxin, YUAN Minhui
Al
x
CrFeCoNi (
x
=0.5, 1) high entropy alloy powder was prepared by gas atomization, and mixed with WC powder by high-energy ball milling to obtain WC-Al
x
CrFeCoNi composite powders. The WC-Al
x
CrFeCoNi composite was prepared by hot pressing sintering. The microstructure, mechanical properties and corrosion behavior of the sintered samples were studied by X-ray diffraction, scanning electron microscopy, Vickers hardness and electrochemical corrosion test. The results show that replacing Co with Al
x
CrFeCoNi high entropy alloy as bonding phase can inhibit WC grain growth and refine grain size. The WC-Al
x
CrFeCoNi has higher hardness and better fracture toughness than traditional WC-10Co cemented carbide. Among them, the WC-10AlCrFeCoNi alloy has the highest hardness of 20.3 GPa, while the WC-10Al
0.5
CrFeCoNi alloy has the maximum fracture toughness of 12.0 MPa·m
1/2
. WC-10Al
x
CrFeCoNi composite has better corrosion resistance than WC-10Co traditional cemented carbide.
2019 Vol. 24 (2): 100-105 [
Abstract
] (
416
)
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756
)
106
Microstructure and properties of powder metallurgy Ti-Zr alloys for dentalimplants
WANG Baoqi, ZHANG Taomei, WANG Jianying, YANG Hailin, RUAN Jianming
Powder metallurgy Ti-
x
Zr alloy (
x
=15, 25, 35, 45, mass fraction, %) were prepared by vacuum sintering technology. The microstructure and phase composition of Ti-Zr alloys were investigated by OM and XRD, the mechanical properties were measured by Vickers hardness tester and universal material testing machine, the friction performance and corrosion resistance were investigated by Rolling friction and wear tester and electrochemical workstation, and the in-vitro cytotoxicity tests (MG-63) were carried out for biocompatibility evaluation. The results indicated that α and α′ phase exist in Ti-
x
Zr alloys, all Ti-Zr alloys show a lower elastic modulus ranging from 53.5 GPa to 59.3 GPa compared with CP-Ti. The alloys presented no cytotoxic effects and the surface of the alloys exhibited great growth conditions for MG-63 cells. Increasing Zr content could lead to increase in mechanical properties, friction performance and corrosion resistance. The Ti-45Zr alloy exhibited the maximum vickers hardness (HV 525), compressive strength (1 599.9 MPa), corrosion potential
E
corr
(-0.255 V) and the minimum volume of friction wear (0.078 3 mm
2
) and friction coefficient (0.3-0.4) which is of great potential for dental applications.
2019 Vol. 24 (2): 106-111 [
Abstract
] (
335
)
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1170
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112
Microstructure and mechanical property of 7056 aluminum alloy produced by spark plasma sintering
HUANG Lanping, HE Jun, LI Song, CHEN Songyi, CHEN Kanghua
The bulk ultra-high strength 7056 aluminum alloys were prepared by spark plasma sintering (SPS) combined with nitrogen atomization process. The effects of sintering temperatures on the density, microstructure and mechanical properties of this consolidated alloy were studied. The results showed that the gas-atomized 7056 aluminum alloy particles of an average of 43.4 μm exhibited a cellular-like dendritic structure with a grain size of about 1-2 μm, obvious solute element segregation was found at grain boundaries. The nearly full dense bulk body could be obtained by spark plasma sintering. It was the yield strength maxium of 284.7 MPa of the consolidated alloy during compression when the sintering temperature was 480 ℃. With the increase of sintering temperature, the yield strength during compression first increased and then decreased. The mechanical properties of the consolidated alloy could be obviously enhanced after solution and aging treatment, the yield strength of alloy was amaxium of 575.9 MPa as sintering temperature was 420 ℃, and gradually decreased with the increase of sintering temperature.
2019 Vol. 24 (2): 112-119 [
Abstract
] (
408
)
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559
)
120
Electrochemical corrosion behavior of binderless TiCN-based cermets in NaOH solution
XIAO Qiaoping, ZHANG Li, LUO Guokai, CUI Yanming, WU Houping, HUANG Long
Four binderless TiCN-based cermets TiC
0.4
N
0.6
, TiC
0.7
N
0.3
, TiC
0.7
N
0.3
-29WC-12TaC and TiC
0.7
N
0.3
-29WC- 12TaC-2Mo
2
C with a relative density greater than 98.5% were prepared by spark plasma sintering (SPS). Scanning electron microscopy SEM observation shows that the average grain size of binderless TiC
0.4
N
0.6
is substantially larger than that of other three groups. Electrochemical corrosion behaviors of binderless TiCN-based cermets in 0.1 mol/L NaOH solution were investigated by potentiodynamic polarization curve and electrochemical impedance spectroscopy. The results show that the corrosion resistance of the cermets in NaOH solution follows the following order, i.e., TiC
0.7
N
0.3
>TiC
0.7
N
0.3
- 29WC-12TaC>TiC
0.7
N
0.3
-29WC-12TaC-2Mo
2
C>TiC
0.4
N
0.6
. The increase of nitrogen and the addition of metal carbides are detrimental to the corrosion resistance of cermets. The oxidation product formed during the corrosion process can act as a passivation film, which results in a pseudo-passivation phenomenon. Binderless TiC
0.7
N
0.3
cermet has the highest relative densification (99.5%) and the best corrosion resistance.
2019 Vol. 24 (2): 120-128 [
Abstract
] (
432
)
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843
)
129
Effect of CVD carbon content on the properties of copper-based powder metallurgy clutch material
WANG Xiufei, LI Bingju, ZHANG Xiang, YI Xu, WANG Bin, TAN Zhoujian
The cutting debris of C/C composites prepared by chemical vapor deposition (CVD) was used as the source of carbon powder. Chemical vapor deposition (CVD) carbon powder/copper-based powder metallurgy friction materials with different CVD carbon powder contents were prepared by powder metallurgy method. The microstructure and composition of the friction surface of the materials were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The mechanical properties, friction and wear properties were also studied. The results show that the brinell hardness, density and compressive strength of CVD carbon powder/copper-based powder metallurgy materials decrease and the open porosity increases respectively with increasing the content of CVD carbon powder. The CVD carbon powder is smooth layer pyrolytic carbon. The main wear mechanism of 1%-2% CVD carbon powder/ copper-based powder metallurgy materials is abrasive wear, and the main wear mechanism of 3%-5% CVD carbon powder/copper-based powder metallurgy materials samples is mixture of abrasive and delamination wear.
2019 Vol. 24 (2): 129-136 [
Abstract
] (
372
)
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734
)
137
Effect of template size of phenolic resin spheres prepared by hydrothermal method on the magnetic properties of ZnFe
2
O
4
hollow spheres
WANG Zhilong, GE Yicheng, RAN Liping, YI Maozhong
The phenolic resin microspheres using resorcinol and formaldehyde as reactants, ammonia as catalyst and anhydrous ethanol as dispersant were prepared by hydrothermal method. The hollow ferrite was prepared templated by phenolic resin microspheres, using ferric nitrate and zinc nitrate, ferric chloride and zinc chloride as precursors, respectively. The structure, morphology and particle size of phenolic resin spheres, as well as the crystal structure, chemical composition, micromorphology and magnetic properties of ZnFe
2
O
4
spheres were characterized. The effect of template sphere size on the magnetic properties of zinc ferrite was investigated. The results show that the size of the phenolic resin sphere decreases with the stirring speed increasing or the amount of formaldehyde decreasing. The phenolic resin balls of different sizes can be obtained by controlling the proportion and amount of raw materials in the reaction system, the spherical surface is smooth, the sphericity is high, the size is uniform, and the monodispersity is good, and the surface contains a large amount of hydroxyl functional groups. ZnFe
2
O
4
is a well-crystallized cubic spinel structure, which is a regular hollow sphere with good dispersibility and uniform size. As the size of the template decreases, the size of the ZnFe
2
O
4
sphere gradually decreases, and it turn out the ferromagnetism transit to paramagnetic, and the saturation magnetization (
M
s) gradually increases. When the template size is 271.8 nm, the saturation magnetization of the ZnFe
2
O
4
sphere is 5.4 (A∙m
2
)/kg.
2019 Vol. 24 (2): 137-146 [
Abstract
] (
347
)
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1251
)
147
Effects of heat treatment on the microstructure and mechanical property of PAN-based carbon fibers
XU Yixi, YANG Fenghao, WANG Xiyun, YI Maozhong
The PAN-based carbon fibers were heat-treated at temperatures ranging from 1 000 ℃ to 1 800 ℃. The microstructure and mechanical properties of the carbon fibers were analyzed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and single-fiber tensile test. The results show that the nitrogen content of PAN-based carbon fibers decreases and the surface roughness decreases first and then increases with increasing the heat treatment temperature. The microstructure in the skin region suggests that the turbostratic graphite structure gradually transforms into a three-dimensional graphite structure during heat treatment. The continuity of the graphite crystallites is improved due to the coalescence between adjacent graphite crystallites. The observation of the fracture morphologies shows that the crack initiation and propagation are controlled by the microstructure and defects of carbon fibers in the skin region. Due to the improvement of the cross-linking between the graphite crystallites, the tensile strengths of carbon fibers heat-treated at 1 200 ℃ and 1 400 ℃ increase to 4.68 GPa and 4.59 GPa respectively, which are higher than that of the as-received carbon fibers. The tensile strength of the carbon fibers is mainly determined by the amount of defects in the skin region, the cross-linking between the graphite crystallites and the interfacial residual stress.
2019 Vol. 24 (2): 147-153 [
Abstract
] (
423
)
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783
)
154
Fabrication and performance of aluminized coating on K403 Ni-based superalloy sintered by spark plasma sintering
JIANG Jun, LI Ruidi, YUAN Tiechui, WANG Yue, WANG Minbo
According to the effect of electric field on atomic diffusion, combined with the advantages of pulse plasma sintering which rapid temperature rise and high cooling rate can be achieved to realize rapidly aluminizing of nickel base alloy. In this paper, the effect of aluminizing temperature on aluminized process of K403 nickel-based superalloy and the high temperature oxidation resistance and wear properties of the Ni-based superalloy were studied. The results show that the aluminized coating with a thickness of about 109 μm is obtained through aluminized at 900 ℃ for 30 min, which belongs to low temperature and high activity aluminizing. The thickness of aluminized layer at 1 000 ℃ is about 89 μm, which belongs to aluminizing at high temperature and low activity. After 1 000 ℃ oxidation, the mass gain from 2.5 mg/cm
2
of untreated nickel-based superalloy decreases to 1.3 mg/cm
2
of the aluminized nickel-base superalloy, reduced by 48%. Meanwhile, the friction coefficient decreases by 50% from 1.2 to 0.6. The volume wear rate decreases from 4.08% to 0.392%, reduced by 90.4%.
2019 Vol. 24 (2): 154-160 [
Abstract
] (
464
)
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(597 KB) (
653
)
161
Effects of process on the microstructure and anti-oxidation property of GH600 nickel-base superalloys for spark plug
WANG Zonghao, YAO Pingping, TAO Shunqiang, CHEN Zhaoke, ZHAO Jian, ZHAO Lin
Nickel-based superalloy used in spark plugs was prepared by casting-electroslag remelting-forging-drawing processes. The effects of the processing on the microstructure and oxidation resistance of the Nickel-based superalloys, especially the phase composition and morphology of the formed oxide layers were studied. The results show that, the grain size of casting alloy is large and pores and impurities were found. Electroslag remelting process can improve the purity of the alloy, while reducing the shrinkage of the material. The forging and drawing process can make the grain of the alloy refinement. The oxide layer on the surface of the casting alloy is incomplete and easy to peel off. Weight gain of the casting alloy after oxidation at 900 ℃ for 100 h is 1.74 mg/cm
2
. With the process of electroslag remelting, forging and drawing, the oxide layer becomes complete and compact. Nodular oxides appear on the surface of forging alloy and drawing alloy, and their antioxidant properties are gradually improved. Weight gain of electroslag remelting, forging and drawing alloys after oxidation are reduced to 1.17, 0.71 and 0.51 mg/cm
2
, respectively. Casting, electroslag remelting and forging alloys form a double-layer oxide layers, the outer oxide layer is mainly composed of NiO and NiFe
2
O
4
, while the inner oxide layer is an enriched area of Cr. After the double-layer oxide layer is formed on the surface of the drawing alloy, a similar double-layer oxide layer is formed inside the alloy, and finally a four-layer oxide layer is formed in drawing alloy.
2019 Vol. 24 (2): 161-167 [
Abstract
] (
418
)
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(821 KB) (
478
)
168
Preparation and characterization of diamond-cemented carbide composites based on co-electroplating process
LUO Guokai, ZHANG Li, CUI Yanming, LIU Tao, XIAO Qiaoping, HUANG Long, WU Houping
Ni-diamond composite was electroplated on WC-10Co cemented carbide substrate by sand-falling process. The effects of main salt concentration, temperature and pH value on the nucleation overpotential of nickel were investigated by cyclic voltammetry to optimize the process parameters of co-electroplating. Based on the optimized process parameters, the effect of substrate pretreatment method on the area fraction of diamonds was investigated. The adhesive strength between the plating and the cemented carbide substrate as well as between the diamonds and the nickel substrate was tested by thermal shock. The results show that, under the process conditions of main salt concentration 280 g/L, temperature 40 ℃, pH4, current density 0.015 A/cm
2
and diamond powder concentration 2.3 g/L, nickel and diamond (W10, with an average particle size of around 10 μm) can be co-deposited with high quality. The plating is chracterized with a dense microstructure, even distribution of diamond and high adhesive strength. The area fraction of diamonds in the plating reaches 36.9% by 1500 mesh diamonds polising and chemical etching.
2019 Vol. 24 (2): 168-175 [
Abstract
] (
379
)
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1256
)
176
Effect of Yb, Zr, Ti additions on the microstructure and mechanical properties of super-high strength Al-Zn-Mg-Cu alloys
FANG Huachan, ZHU Jiamin, CHEN Zhuo, LIU Tan
Four kinds of Al-Zn-Mg-Cu alloys adding Yb, Zr, Ti were prepared by cast metallurgy. Effects of Yb-Zr, Zr-Ti, Yb-Ti, Yb-Zr-Ti additions on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloy were compared by optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), hardness and tensile test. The results show that, the Al-Zn-Mg-Cu alloy with Yb-Ti additions forms obvious subgrain boundaries during hot extrusion. After solution treatment, the alloys with Yb-Ti and Zr-Ti additions have obvious recrystallization. The alloys with Yb-Zr and Yb-Zr-Ti have obvious effect of restraining recrystallization due to the precipitation of a large number of coherent Al
3
(Zr,Yb) dispersed phases with size of 10-20 nm. Micron-sized Al
8
Cu
4
Yb and Al
20
Ti
2
Yb phases are precipitated in Al-Zn-Mg-Cu alloy with Yb-Ti addition, which induce the matrix recrystallization. Al-Zn-Mg-Cu-Yb-Zr alloy without recrystallization has the highest mechanical properties and fracture toughness, the ultimate strength, yield strength, elongation and fracture toughness are 721.9 MPa, 711.5 MPa, 9.7 %, 29.3 MPa·m
1/2
, respectively, and exhibits complete dimple fracture characteristics. The mechanical properties of Al-Zn-Mg-Cu-Yb-Ti alloy with complete recrystallization are the lowest, and the fracture mode is complete intergranular fracture.
2019 Vol. 24 (2): 176-187 [
Abstract
] (
406
)
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(1673 KB) (
522
)
188
Flexural property of C
f
/Cu/C composites
ZHANG Huan, YIN Jian, XIONG Xiang, ZHANG Hongbo, XU Ya’nan, YANG Peng’ao
Using non-woven fabric/fibre web/copper mesh (A-type) and fibre web/copper mesh (B-type) as reinforcements, three kinds of C
f
/Cu/C composites were prepared by chemical vapor infiltration and impregnation- carbonization with resin carbon method. The percentage of pyrolytic carbon were 38% (M1), 29% (M2), 19% (M3) in the matrix. Respectively the flexural property of the composite was measured on Instron- 3369 mechanical testing machine. The effects of type of preform and pyrolytic carbon content on mechanical property were investigated. The results show that with the decrease of pyrolytic carbon content, the flexural strength of A-type and B-type composites decreases gradually in vertical and parallel direction. For the same specimen, the flexural strength of C
f
/Cu/C composites in the vertical direction is better than that of parallel direction, but the difference is small. Compared with B-type C
f
/Cu/C composites, A-type C
f
/Cu/C composites have better mechanical property. When the bending is carried out, carbon fibers from pyrolytic carbon and resin carbon layers are pulled out, and fracture morphology is step-like.
2019 Vol. 24 (2): 188-194 [
Abstract
] (
368
)
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(591 KB) (
689
)
195
Effect of graphite surface modification on microstructure and properties of Cu-based friction materials
LIU Tan, XIAO Peng, FANG Huachan, LI Jinwei, ZHU Jiamin, CHEN Zhuo, WU Junbo
Cu-based friction material were prepared by powder metallurgy technology with natural flake graphite and phenolic resin coated graphite as lubricating components. The effects of graphite surface modification on the microstructure, physical properties, mechanical properties and friction and wear properties of Cu-based friction materials at different braking speeds were studied. The results show that, compared with natural flake graphite/copper-based friction materials, the Cu-based friction materials with resin-coated graphite powder have more uniform graphite distribution, denser copper matrix, higher density, lower porosity, higher flexural strength and compressive strength. When the braking velocity is 5 500 r/min, the wear extent of the phenolic resin-coated graphite/Cu-based friction material is reduced by 24%, the matching plates wearing capacity is reduced by 40%, and the braking time is shortened by 11%. Compared with the natural flake-graphite, the deformation and failure of the resin coated graphite material decreases obviously, and the friction and wear properties of the resin coated graphite material increases.
2019 Vol. 24 (2): 195-204 [
Abstract
] (
358
)
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(1378 KB) (
946
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