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2018 Vol. 28, No. 04
Published: 2018-08-10
1
The research and development of powder metallurgy superalloy
HU Lian-xi，FENG Xiao-yun
DOI: 10.13228/j.boyuan.issn1006-6543.20180067
Powder superalloy is a key material for manufacturing rotating components that high-performance aero-engine turbine discs. Segregation of components is limited into the powder particles， which can eliminate the macroscopic segregation of conventional casting and has the advantages of uniform microstructure and fine grains， obtaining good yield strength and fatigue properties. The development， preparation methods and consolidation process of powder superalloy were summarized. In addition， the main defects existing in powder superalloy were described. The development status of laser additive manufacturing technology was also summarized， and the research progress of numerical simulation of powder superalloys was briefly demonstrated. Finally， according to the domestic demand situation of powder superalloy， the development direction of powder superalloy in the future was predicted.
2018 Vol. 28 (04): 1-7 [
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Characterization of micro/nano copper powder for vehicle capacitors prepared by liquid phase reduction method
DONG Bin，ZHANG Yong-xue，WU Yue-wu
DOI: 10.13228/j.boyuan.issn1006-6543.20170065
The micro/nano copper powder for vehicle capacitors was prepared by liquid phase reduction method. The effects of pH value and mixing method on the composition， morphology and particle size of the product were studied by X-ray diffraction and scanning electron microscope. The results show that when the pH value of the solution is 6 or 8， the product is Cu powder with face-centered cubic structure. As the pH value increases to 10， there is Cu2O phase in addition to the metal Cu in the product. The shape of copper particles is irregular smooth polyhedral structure， and the particle size decreases with the increase of pH value. Under the same experimental conditions （pH＝3）， the copper powder particles mixed by pouring method have narrow particle size distribution， the particle size is about 1 μm， which has good dispersibility.
2018 Vol. 28 (04): 8-11 [
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Study on surface passivation process of iron-silicon powder
LI Wei-jian，LI Yuan-yuan
DOI: 10.13228/j.boyuan.issn1006-6543.20170168
In order to study the surface passivation process of soft magnetic metal powder， gas atomized iron-silicon powder was used as raw material to prepare passivation powder under different passivation conditions， and the passivation powder was pressed into magnetic rings. The surface morphology of passivated powder was observed by scanning electron microscopy （SEM）， and the magnetic ring properties were tested. The results show that with the increase of reaction temperature or the decrease of pH value of reaction solution， the density and permeability of the magnetic core decrease， and the insulation resistance and compressive strength increase. Through the comparison of data， the passivation process with high permeability and high insulation resistance is obtained， that is， the mass ratio of Fe-Si powder and aluminum dihydrogen phosphate solution with pH 3.0 is 1∶1， and the reaction is carried out at 50 ℃ for 15 min. The magnetic ring has the best performance， the relative permeability is 36.3， the insulation resistance is 57 mΩ， the density is 7.24 g/cm3， and the compressive strength is 6.0 MPa.
2018 Vol. 28 (04): 12-16 [
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17
Effect of TiAl target preparation process on properties of hard coatings
DAI Hu-min，XU Ju-zhong
DOI: 10.13228/j.boyuan.issn1006-6543.20170163
TiAl alloy targets were prepared by pressureless sintering and hot pressing sintering respectively， and TiAl hard coatings were prepared by sputtering deposition method. The microstructure and phase composition of the hard coatings were analyzed， and the high temperature oxidation resistance and mechanical properties of the coatings were also tested. The results show that the hard coating of target material prepared by pressureless sintering is poor in compactness， uneven in dispersion， fast in oxidation rate and only 1 798 HV in microhardness. While the hard coating of target material prepared by hot pressing sintering has the advantages of high density， low porosity， fine grain size， uniform distribution， significantly improved oxidation resistance， which microhardness is as high as 3 165 HV， 76% higher than the former.
2018 Vol. 28 (04): 17-20 [
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21
Effect of nano-composite grain inhibitors on composition and microtructure of WC-TiC-Co cemented carbide prepared by microwave method
ZHENG Juan，ZHAO Zhi-wei，LIU Xiao-fang ，CHEN Fei-xiao，YANG Bao-zhen
DOI: 10.13228/j.boyuan.issn1006-6543.20170042
The effect of composite grain inhibitor on the composition and microstructure of cemented carbide was studied by using nano WC， TiC and Co powder as raw materials and nano V8C7-Cr3C2 composite powder as grain inhibitor. The results show that the nano V8C7-Cr3C2 composite powder synthesized by microwave in-situ exhibits good dispersity and consists mainly of spherical or quasi-spherical particles with an average size of about 30 nm. After microwave sintering， WC-based composite powder is mainly composed of WC and TiC， and the diffraction peak intensity of WC is obviously weakened. After adding nano-composite grain inhibitor， the distribution of hard phase is uniform and the average grain size is about 500 nm.
2018 Vol. 28 (04): 21-25 [
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Study on compressive properties of aluminum foam with small pore size at low strain rate
WANG Jun-de，CHEN Gui-qing
DOI: 10.13228/j.boyuan.issn1006-6543.20170036
The compressive properties of aluminum foam with small pore size at low strain rate were studied by using 6061 aluminum alloy powder as raw material and TiH2 powder as foaming agent. The results show that the pore size of aluminum foam prepared by powder metallurgy method is small and the pore structure is uniform. With the increase of compression pressure， aluminum foam undergoes three stages： elastic deformation， collapse deformation and densification. The static compressive stress-strain curve of aluminum foam is arc-shaped. With the increase of strain， the stress of aluminum foam with different porosity shows the same trend. The energy absorption capacity of aluminum foam is directly proportional to the strain and inversely proportional to the porosity. However， the energy absorption efficiency is proportional to the porosity， and increases at first and then decreases with the increase of the strain.
2018 Vol. 28 (04): 26-30 [
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31
The HVOF spraying parameters optimization of CoCrW coating and the effects of microstructure on adhesion strength
Lü Yan-hong，ZHANG Qi-fu
DOI: 10.13228/j.boyuan.issn1006-6543.20160141
The HVOF spraying parameters of CoCrW coating were optimized by using four factors and three levels orthogonal test method， the microstructure of coating was taken as objective to analyse the results and the adhesion strength of coating with substrate prepared by using optimized parameters were tested. The results show that the best process parameters is 897 L/min for the oxygen flow， 22 L/h for the kerosene flow， 66 g/min for the feed rate and 340 mm for the spray distance. The adhesion strength of CoCrW coating with substrate is 69.7 MPa at these parameters. The analysis shows that in HVOF spraying process， high-speed moving particles impact the matrix to produce shot peening effect. At the same time， kinetic energy is converted into thermal energy in a short time， which makes molten particles produce secondary plasticization at the interface. It is beneficial to the rapid spreading of the molten droplets， enhances the compactness of the coating and improves the bonding strength between the coating and the substrate.
2018 Vol. 28 (04): 31-36 [
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37
Study on preparation of copper-base tee parts by warm flow compaction
YANG Yi，DING Tao，NI Dong-hui
DOI: 10.13228/j.boyuan.issn1006-6543.20170098
The near net-shape manufacturing process of complex parts is always the development goal of warm flow compaction technology. The copper-based powder material was used as the research object， and the tee part green body was pressed at 85 ℃ by using the warm flow compaction process. Through a reasonable degreasing and sintering process， the tee part sample was successfully prepared. The degreasing process， microstructure and density of the sample were also analyzed. Results show that the copper-based tee sintered part without significant surface defects is obtained by keeping the temperature at 300 ℃ and 450 ℃ for 30 min respectively and slowly heating to 950 ℃ for sintering for 60 min. However， the parts density distribution is not uniform after sintering， and the lateral part density is significantly lower than the axial part.
2018 Vol. 28 (04): 37-41 [
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42
Effect of Nd2O3 addition on the sintering properties of dolomite
ZHANG Wang-nian，DENG Ning，WANG Yong
DOI: 10.13228/j.boyuan.issn1006-6543.20160148
Adding various contents of Nd2O3 into natural dolomite， magnesium-calcium materials were prepared by two-step calcination method， and the influence of Nd2O3 on sintering properties of dolomite was studied. The results show that the bulk density of samples without Nd2O3 is 3.25 g/cm3， the apparent porosity is 3.8%， and the MgO grain size is 3.82 μm when sintered at 1 600 ℃ for 3 h. When 0.75% （mass percent） of Nd2O3 is added， the activation energy of grain growth is decreased due to the solid solution reaction of Nd2O3 with MgO and CaO. The bulk density of the sample increases to 3.33 g/cm3， the apparent porosity decreases to 2.8%， and the MgO grain size increases to 4.53 μm.
2018 Vol. 28 (04): 42-46 [
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47
Effect of CeO2 content on microstructure and mechanical properties of SiC particle reinforced aluminum matrix composites
ZHU Peng-fei，XIE Jing-pei，，WANG Ai-qin，，LI Jian-yun
DOI: 10.13228/j.boyuan.issn1006-6543.20170003
In order to study the effect of CeO2 on microstructure and mechanical properties of SiCp/Al-12Si composites， the composites were prepared by powder metallurgy method with micro-sized SiC particles and Al-12Si-Cu-Mg alloy powder as raw materials and CeO2 powder added. The microstructure of the material was characterized and analyzed by SEM and EDS， and its physical and mechanical properties were tested. The results show that the addition of appropriate CeO2 can significantly refine the precipitated Si， and the distribution of Si phase particles is more uniform. The density， tensile strength and elongation of the composite are significantly improved， and the coefficient of thermal expansion is significantly reduced. When the volume fraction of CeO2 is 0.2%， the properties of the composite reach the optimal values， which are 98.38%， 376.9 MPa， 4.09 % and 13.94×10-6 K-1， respectively.
2018 Vol. 28 (04): 47-51 [
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52
Effect of Cu-Sn alloy addition on the performance of friction material for vehicle braking
LIU Li-na， ZHANG Ming-ming
DOI: 10.13228/j.boyuan.issn1006-6543.20170008
The mechanical properties， friction properties and friction surfaces of copper-tin alloy friction materials for vehicle braking were characterized， and the effects of different copper-tin alloy additions on the performance of friction materials were analyzed. The results show that the density of friction materials gradually increases， and the pH value remains almost unchanged， the hardness first increases and then decreases， compressive stress first decreases and then increases， and shear strength changes little with the increase of Cu-Sn alloy content. With the increase of brake pressure， the friction coefficient of all samples decreases. A relatively complete friction film is formed on the surface of the sample with 15% （mass percent） copper-tin alloy， but the friction film peels off to some extent.
2018 Vol. 28 (04): 52-55 [
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Research progress on the preparation methods of metal powder for 3D printing
CHEN Ying-ying，XIAO Zhi-yu，LI Shang-kui，ZOU Hai-ping，LI Bo
DOI: 10.13228/j.boyuan.issn1006-6543.20160153
Since 2015， China has officially incorporated 3D printing into the key direction of national industrial transformation and upgrading. Metal powder for 3D printing is the value of 3D printing technology， and more and more researchers are committed to researching high-quality and low-cost metal powder preparation technology for 3D printing. Gas atomization technology has the advantages of high production efficiency， low cost and good sphericity of prepared powder， which can meet the special requirements of metal powder for 3D printing. The development history and current situation of metal or alloy powder preparation technology at home and abroad were expounded， the gas atomization powder preparation technology was emphatically discussed， and the problems and development trends of metal powder for 3D printing were pointed out.
2018 Vol. 28 (04): 56-61 [
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Research progress on the effect of the third component addition on binary immiscible system alloys with nano-composite structure prepared by mechanical alloying
WU Jiang，WU Zhi-fang，ZHANG Lei
DOI: 10.13228/j.boyuan.issn1006-6543.20160143
The binary immiscible system alloys with nano-composite structure prepared by mechanical alloying show the unique properties compared with micro-scale structure. The third component is generally added into binary immiscible system alloys to further improve their comprehensive properties. The effect of the third component addition on binary immiscible system alloys with nano-composite structure prepared by mechanical alloying was reviewed， with focus on the microstructure and properties.
2018 Vol. 28 (04): 62-67 [
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Discussion on design of gas tightness detection equipment based on powder metallurgy products
YANG Hui
DOI: 10.13228/j.boyuan.issn1006-6543.20170019
A kind of equipment used for gas tightness detection of powder metallurgy products was briefly described， the overall structure and control system of the gas tightness detection equipment were introduced， and the hardware design of the electrical control system was discussed. The gas tightness detection equipment has the advantages of simple structure， safety and reliability， low cost and convenient use， which well meets the requirements of detection work. The gas tightness detection technology in the future will be further developed in the direction of high accuracy， high efficiency and intelligence.
2018 Vol. 28 (04): 68-70 [
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Research and design on cooling system of hot stamping die
PANG Li-juan，ZHANG Xue-feng，HUANG Zhi-yong
DOI: 10.13228/j.boyuan.issn1006-6543.20170023
In order to solve the problem of uneven strength in different parts of ultra-high strength steel hot stamping parts， the heat transfer process during pressure maintaining and cooling stage under different cooling conditions was simulated and analyzed through Deform software. The results show that the die surface temperature decreases rapidly by 50.0-100.0 ℃ in the pressure maintaining stage after cooling water is introduced. By optimizing the arrangement of cooling channels， the number and diameter of cooling channels and the cooling water flow velocity， the temperatures at the fillet of male die and female die decrease by 14.5 ℃ and 26.0 ℃ respectively. The optimal design scheme of mold cooling system is applied to the hot stamping mold of A-pillar reinforcement part， the uniform martensite structure is finally obtained， which is beneficial to obtain parts with consistent mechanical properties.
2018 Vol. 28 (04): 71-76 [
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Study on the remanufacturing technology for sintered Nd-Fe-B magnets bulk wastes adding Ce
MEI Li-ping
DOI: 10.13228/j.boyuan.issn1006-6543.20180018
During the recycling process of sintered Nd-Fe-B magnets， rare earth elements will be oxidized and lost， thus the densification of the recycled magnets is interfered. The addition of Ce metal is helpful to densify the recycled magnet and optimize the microstructure of the magnet. Through the addition of low-cost Ce metal， the comprehensive performance of the recycled magnet was successfully optimized. The hydrogen absorption process of waste sintered Nd-Fe-B magnets was also studied. The magnetic properties of the recycled magnets were tested by BH tester， and the microstructure of the magnet was observed by scanning electron microscopy. The results show that when 4% Ce （ mass percent ） is added， the remanence of the recycled magnet reaches more than 98% of that of the original magnet， and the intrinsic coercivity exceeds that of the original magnet under the conditions of 1 350 K sintering and 773 K heat treatment.
2018 Vol. 28 (04): 77-81 [
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Methods to improve the density of the center and top of powder metallurgy automobile water pump hub
Lü Hao
DOI: 10.13228/j.boyuan.issn1006-6543.20170020
Powder metallurgy automobile water pump hubs generally require a large clasp force （also known as the force fell off the hub）， good wear resistance， high strength， good corrosion resistance， etc. Such requirements make a high demand for equipment， molds， processes， etc.， of which the clasp force is the most important. The upper end of the automobile water pump hub is mostly a conical surface， and the structure is quite special. During pressing， it is easy to cause a low density in the center and top ends. The clasp force is depending on the density in the case that other conditions are equal. Therefore， in order to improve the clasp force， it is necessary to increase the center and top density of the hub. Starting from the actual production and the basic structure of the hub， three methods to increase the density of the center and top of the hub were introduced.
2018 Vol. 28 (04): 82-85 [
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