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Quick Search     Adv Search   2021 Vol. 31, No. 04 Published: 2021-08-10   1 Materials development of powder metallurgy valve seat inserts and their failureResearch progress of Al series high-entropy alloy prepared by selective laser melting Hot! WUWenheng，ZHANG Liang，LU Lin DOI: 10.13228/j.boyuan.issn1006-6543.20210090 The high entropy alloy has broken the shackles of the traditional alloy design and become one of the hot spots in the 21st century due to its excellent properties, among which the Al system high entropy alloy is particularly outstanding. Selective Laser Melting (SLM) is an additive manufacturing technology for direct manufacturing of three-dimensional metal parts with complex shapes. There is no need to make molds, and the time for mold design and manufacturing can be omitted, which greatly reduces the product development cycle, saves development costs, and is feasible. The economic benefits of the new alloy have unique advantages in tapping the performance and application potential of new alloys. Inconclusion, the application of SLM technology to the preparation of high-entropy alloys can be described as a "strong combination". This article will introduce in details the research results of SLM technology in the preparation of Al series high-entropy alloys in recent years, review the research progress of the microstructure and performance improvement of Al series high-entropy alloys formed by SLM technique, and point out the importance and difficulty of the current SLM process of Al series high-entropy alloys. Based on this, we look forward to the future research, application and development of laser selective melting and forming of highentropy alloys. 2021 Vol. 31 (04): 1-10 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 11 A comparative research of porosity in stainless steel powders manufactured by vacuum induction-melting gas atomization and plasma rotating electrode process Hot! HU Jiaqi，WANG Changjun，WEI Lai，YANG Zhe，LIANG Jianxiong，DONG Han DOI: 10.13228/j.boyuan.issn1006-6543.20190073 In this paper, a comparative research on the characteristics of porosity in stainless steel powders manufactured by vacuum induction-melting gas atomization (VIGA) and plasma rotating electrode process (PREP) were conducted via metallographic examination. The results show that the number of hollow powders increases with the increment of particle size in both powders. Meanwhile, the morphology of porosities primarily exhibites a spherical shape. The forming mechanisms of porosity in VIGAed and PREPed powders are quite different in essence. The atomization is accompanied by the rapid cooling of droplets during VIGA process. The incomplete bag breakup during secondary breakup stage causes gas preservation inside the liquid film. Considerable hollow powders form after droplets solidification due to the gas preservation. While in the case of PREP with low pressure of gas (0.1 MPa), a minute amount of gas enters into the core of melted end face under the negative pressure generated from high-speed rotation of the metal bar. The invaded gas would further move along with the liquid film. The gas-containing liquid film forms droplets under the control of centrifugal force. Consequently, a small amount of hollow powders with porosity are produced after solidification during PREP. 2021 Vol. 31 (04): 11-15 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 16 The study on degassing behavior of nickel-base superalloy FGH96 powder Hot! LUO Xuejun，ZHANG Lichong，LI Zhou，CHEN Hao DOI: 10.13228/j.boyuan.issn1006-6543.20210041 The degassing behavior of nickel-base superalloy FGH96 powder was studied by means of temperature programmed desorption mass spectrometry (TPD- MS), field emission scanning electron microscopy (FE- SEM) and X-ray photoelectron spectroscopy (XPS). The results show that under the condition of helium purging, the desorption of hydrogen (H2), water (H2O), carbon monoxide (CO) and carbon dioxide (CO2) occurres on the surface of the powder with the increase of degassing temperature. The desorption of hydrogen and carbon monoxide mainly occurres in the heat preservation stage, and the desorption of water and carbon dioxide mainly occurres in the heating stage. During the degassing process, oxides such as TiO2, Cr2O3, and Nb2O5 on the powder surface do not decompose and deoxidize, while hydroxides such as Ni(OH)2 are hydrolyzed and deoxidized to generate Ni element. The effect of temperature on degassing behavior of the FGH96 superalloy powder is significant. For the FGH96 superalloy powder used in this study, the degassing temperature is recommended to be 350-450 ℃ within 1 h under helium purging conditions. 2021 Vol. 31 (04): 16-21 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 22 Numerical simulation and mechanism analysis of gas atomized pulverizing process for additive manufacturing Hot! WANG Changjun，LIU Yu，CAO Chengxiang，LANG Tong，MAConghui，XIE Yanjun DOI: 10.13228/j.boyuan.issn1006-6543.20210071 Using a numerical approach of computational fluid dynamics (CFD), the effects of atomizing gas temperature and pressure on the supersonic flow field distribution and powder yield were studied in comparison to industrial production data. The result shows that with the atomized gas increased, the average temperature and velocity of the atomization area increase, which is theoretically beneficial to the finer powder production. Besides, as the pressure of the atomized gas increases, the average temperature of atomized region reduces and the average velocity increases. Furthermore, with the pressure of atomized gas increased, the impact of temperature on the yield of finer powder gradually weakens, and even resulting in worse powder yield in case of high-pressure atomized gas. Hereby, the increased yield of finer powder is dominated by the additional pressure of atomized gas. Comprehensively, the parametric optimization should be carried out to ensure the high production efficiency of finer powder and reduce the manufacturing cost. 2021 Vol. 31 (04): 22-28 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 29 Effect of graphene content on hardness and conductivity of copper matrix composites Hot! WANG Shaopeng，WEI Kunxia，JIA Feilong，DU Qingbo，WEIWei DOI: 10.13228/j.boyuan.issn1006-6543.20200195 Graphene copper matrix (Gr/Cu) composites were prepared by powder metallurgy, and sodium dodecyl sulfate (SDS) was used as dispersant to study the influence of graphene content on the microhardness and conductivity of the composites, so as to determine the optimal content of graphene in copper matrix to obtain high hardness and high conductivity graphene copper matrix composites. The results show that graphene is evenly distributed in the composites. After adding graphene, the hardness of copper matrix increases, while the conductivity decreases. When the content of graphene is 0.5%, the composite has high hardness and good electrical conductivity. The microhardness is increased by 25% to 57HV0.025, and the conductivity is 84%IACS. 2021 Vol. 31 (04): 29-34 [Abstract] ( 4 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 35 Effect of axial turbine structure on mixing effect of ZrO2 ceramic powder prepared by dry method Hot! YU Dongling，ZHU Zuoxiang，ZHOU Jiangen，HUANG Jiawen，WU Nanxing DOI: 10.13228/j.boyuan.issn1006-6543.20200151 In order to investigate the effect of axial turbine structure on the rotating coupled flow field of dry prepared ZrO2 ceramic powder, the mathematical model of gas-solid two-phase flow was established, and the powder numerical models of ZrO2 rotating coupling chamber with four different axial turbine structures were established by CFD method. The volume fraction nephogram and velocity field nephogram of ZrO2 powder were analyzed, and the internal relationship between mixing effect of rotating coupling flow field of ZrO2 ceramic powder and different axial turbine structure was explored. At the same time, the experimental platform of dry preparation of ZrO2 powder was built, and the micro morphology and sphericity of the powder were analyzed to verify the correctness of the numerical simulation. Numerical analysis shows that the axial opening turbine structure overcomes the difficulties of strong radial flow and weak axial flow, and the enhanced axial flow is more distributed in the upper and middle parts of the rotating coupling chamber. The uniformity of ZrO2 ceramic powder is the best, and the proportion of volume distribution is between 0.7- 0.8, and there is no obvious accumulation phenomenon. The results show that the shape of ZrO2 powder prepared by turning on the turbine structure is regular, and the sphericity is about 0.72. The experimental results are consistent with the simulation results, which verifies the accuracy of the numerical simulation. 2021 Vol. 31 (04): 35-42 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 43 Effect of Ce doping on microstructure and magnetic properties of Nd-Pr-Ce-Fe- Al-B as-spun ribbons Hot! HE Younian，GUO Zhaohui，FANG Yikun，JING Zheng，YUAN Zikai，ZHU Minggang DOI: 10.13228/j.boyuan.issn1006-6543.20200294 [(Nd0.76Pr0.24)1-xCex]12Fe79Al3B6 (x = 0~0.3) series melt as-spun ribbons with diffrent Ce content were prepared, and their microstructures and magnetic properties were investigated. The experimental results show that the magnetic properties of the as-spun ribbons decrease with the increasing of Ce content, however, abnormal increases appear for the x = 0.2 ribbon with Hcj=8.38 kOe, Br=8.68 kGs and (BH)max=14.42 MGOe. HRTEM/EDS results reveal that the average grain size of the x = 0.2 as-spun ribbon is about 28 nm, which is the most uniform and finest among all the ribbons, and the grains of the 2:14:1 phase possess significantly high component fluctuation, indicating that phase separation has occurred. The abnormal increases in magnetic properties of the x = 0.2 as-spun ribbon is mainly contributed to both the grain refinement and the phase separation. 2021 Vol. 31 (04): 43-48 [Abstract] ( 4 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 49 Preparation and performance of WC/TiC reinforced iron matrix composites Hot! YE Xuan，QIN Ling DOI: 10.13228/j.boyuan.issn1006-6543.20190258 TiC and WC/TiC were added into Fe-1.5Cu-1.8Ni-0.5Mo-1C and Fe-1.5Cu-0.7C. Composites were prepared by conventionally mixed powder in mesh belt sintering furnace. Material properties were tested including microscopic pore morphology, density, hardness and bending strength. The results show that compared with WC, the interface bonding between TiC and Fe-1.5Cu-1.8Ni-0.5Mo-1C/Fe-1.5Cu-0.7C is poorer. When TiC is added, materials have the worst performance, which declines as TiC content increases. When WC is added, materials have the best performance, which first increases and then decreases with the increasing of WC content. When TiC and WC are added at the same time, materials have the moderate performance, which also declines as TiC and WC content increases. Under the experiment condition of this paper, adding the right amount of WC to Fe-1.5Cu-1.8Ni-0.5Mo- 1C/Fe-1.5Cu-0.7C as reinforcing particles may be a better choice. 2021 Vol. 31 (04): 49-54 [Abstract] ( 4 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 55 Microstructure and friction properties analysis of Cr3C2 coating on Ni alloy surface prepared by sintering Hot! LIU Lingge，ZHU Jingjin，TIAN Hailan，LIU Lingling DOI: 10.13228/j.boyuan.issn1006-6543.20190088 The Cr3C2 coating was prepared on the surface of nickel alloy used in engine by plasma spraying and the electric contact sintering. The microstructure, wear resistance and other mechanical properties of the coating were tested and analyzed. The results show that the porosity obtained by electrical contact sintering is lower than that obtained by the plasma spraying, and some well-distributed carbides are formed in the substrate, and the density of coating microstructure is significantly increased. The electrical contact sintering method can significantly improve the bonding strength of coating. The friction coefficient increases firstly and then decreases with the changing of temperature. The wear rate of coating remains basically stable at each temperature. The wear morphology of samples does not change significantly between room temperature and 400 ℃. When the temperature reaches 600 ℃, oxidation of the substrate and coating is caused, and fluoride is softened and more oxides generates. With the increasing of temperature, Cr and C elements in the wear surface of Cr3C2 coating first increase and then decrease, while O element shows first decreases and then increases. 2021 Vol. 31 (04): 55-58 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 59 Effect of sintering processing on compressive behavior of porous TNTZ alloy Hot! LI Boqiong，XIE Ruizhen，WEN Kai，ZHANG Jinhui DOI: 10.13228/j.boyuan.issn1006-6543.20200173 Porous Ti-Nb-Ta-Zr alloy with Science and low modulus has become a research hot spot of biomedical implant materials because of its non-toxic elements, excellent biocompatibility, high strength and remarkable plasticity. In order to improve the osseointegration ability of the implant and make it biologically fixed with the host bone, porous Ti-Nb-Ta-Zr alloy including β matrix and a small amount of second phases was prepared by powder metallurgy using space holder method. The results show that with the increaseing of sintering temperature and time, the density and binding strength of porous Ti-Nb-Ta-Zr alloy increase, however, when the sintering temperature (or time) exceeds 1 200 ℃ (or 2 h), the compressive Young's modulus and yield strength decrease. It is related to the crystal growth degree, the composition and distribution of the second phase in the alloy. The fractograph of porous TNTZ alloy is mainly composed of cleavage surface, transcrystalline fracture with the cleavage of similarly oriented laths in a colony and dimples, showing good plasticity. 2021 Vol. 31 (04): 59-65 [Abstract] ( 5 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 66 Research on fatigue behavior of the Fe-2Cu-2Ni-1Mo-1C alloys prepared by spark plasma sintering Hot! TANG Yu，ZHENG Donghai DOI: 10.13228/j.boyuan.issn1006-6543.20210012 Fe-2Cu-2Ni-1Mo-1C alloys were prepared by spark plasma sintering, and the influence of different sintering tempreture on the properties and structures were studied. The results show that specimen sintered at 820 ℃ has a fine and uniform structure, and it possesses good transverse fracture strength and hardness, which are 2 430 MPa and 42HRC respectively. The specimen possesses fatigue strength of 694 MPa at 106 cycles under ultrasonic symmetric bending fatigue test. The fatigue cracks initiate from the surface of the specimen, and the fatigue zone exhibits fatigue striations which means good toughness. 2021 Vol. 31 (04): 66-71 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 72 Friction properties of MoS2/Ag lubricated coating sprayed by plasma spray on rotating shafts Hot! LI Can，ZHANG Zhongxin DOI: 10.13228/j.boyuan.issn1006-6543.20200255 In order to improve the lubrication performance of the surface of mechanical rotating shaft, the MoS2/ Ag coating was prepared on the surface of 1Cr18Ni9Ti stainless steel by plasma spraying (APS) process. The microstructure and friction properties of the coating were studied. The results show that there are metal phase components in the MoS2/Ag coating, the high temperature will cause the melting of the two kinds of metal powder particles and the coating with dense structure is obtained. Ag powder has co-deposited with MoS2 in high temperature environment, and the elemental composition of each coating is basically the same as that of spraying powder. When 20%Ag is added to the coating, the friction coefficient is lower at all temperatures compared with other Ag content coatings. When the temperature increases to 650~850 ℃, the wear rate decreases with the increase of Ag content in the coating. The 20%Ag coating has the smoothest wear surface and no peeling or furrowing occurs. The Ag coating provides good lubrication. The Ag2MoO4 with lamellar structure is formed by chemical reaction between Ag and Mo at high temperature, and good lubricity is obtained. 2021 Vol. 31 (04): 72-76 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 77 Microstructure and properties of Ni based laser cladding coating on AZ91D magnesium alloy Hot! ZHANG lijie，WANG bohua DOI: 10.13228/j.boyuan.issn1006-6543.20200279 With Ni-Cr-Fe alloy powder and Al coated nickel powder as coating material, cladding alloy coating was prepared by laser cladding on AZ91D alloy. The microstructure and properties of the coating were tested. The results show that the comprehensive properties of the coating are the best when the content of Ni-Cr-Fe alloy powder is 30% . The thickness of cladding layer is 827 μm,the dilution ratio is 22.62%, the coating area is 1 000～3 000 μm and the hardness is 758~819HV0.5. In the SEM microstructure of the cladding coating, the petal structure composed of Ni, Cr and Al is the most; XRD analysis shows that the phase is mainly composed of γ-Ni，α-Cr，FeNi3， Fe3Ni2，Cr2Ni3 and (Cr，Fe)7Al. The average friction coefficient is 0.28 and the wear amount is about 2.7 mg. In the fracture toughness test, there is no expansion crack at the indentation, the indentation thickness is relatively uniform, the shape is clear and visible, and the symmetry is good, showing anisotropic fracture characteristics in the direction perpendicular to the interface. The results of high temperature oxidation test shows that the weight gain rate of the coating is slowing down, which indicats that the coating improves the possibility of protecting AZ91D magnesium alloy from high temperature. 2021 Vol. 31 (04): 77-81 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 82 Research progress on the gas atomization for producing metal powders Hot! ZHU Panxing，SHI Shenghe，YANG Jian，ZHANG Chao，ZHAO Xinming DOI: 10.13228/j.boyuan.issn1006-6543.20210003 Gas atomization is a widely used process for manufacturing high performance powders of metals and alloys. The characteristics of powders produced by gas atomization are related with the break up mechanisms of molten metal and process parameters greatly. Based on these, this article expounds the break up mechanisms of molten metal and the factors influencing the performances of powders, aiming to provide some information on the research and development of gas atomization. 2021 Vol. 31 (04): 82-87 [Abstract] ( 4 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 88 Domestic research status of plasma rotation electrode process equipment Hot! YANG Hongtao，LU Zhihui，SUN Zhiyang，ZHANG Leile，YOU Guangfei，CHEN Chao DOI: 10.13228/j.boyuan.issn1006-6543.20200190 With the rapid development and application of additive manufacturing and powder metallurgy technology, the demand for metal powder is increasing. Compared with other powder preparation process, metal powders prepared by plasma rotation electrode process (PREP) have obvious advantages in powder characteristics, which make them ideal forming materials for additive manufacturing and powder metallurgy. The development status of PREP technology domestic and abroad was introduced, the key technical characteristics were analyzed, and then the future development of PREP technology was prospected. 2021 Vol. 31 (04): 88-93 [Abstract] ( 6 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 94 The development status and trend of thermal spraying technology towards artificial intelligence era Hot! WANWeiwei，CHEN Xinhua，QU Lianshi，BEI Guoping DOI: 10.13228/j.boyuan.issn1006-6543.20210045 Thermal spraying technology is an important part of material surface engineering, and it has been widely used in advanced manufacturing field and has been developed and improved continuously. The emergence of artificial intelligence provides a new way for the development of thermal spraying technology vitality. This paper first introduces the basic research status of thermal spraying and the main technical challenges have to be solved. Secondly, it introduces the principle, advantages and disadvantages of the main thermal spraying methods as well as their applications. Finally, it expounds the application of artificial intelligence technology in the development of thermal spraying technology from the aspects of process control and spraying equipment. 2021 Vol. 31 (04): 94-99 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 100 Crack analysis of PM engine bearing pedestal Hot! DING Xia，WU Zengqiang DOI: 10.13228/j.boyuan.issn1006-6543.20210031 This paper analyzed and studied the chemical composition, density, hardness, metallography and fracture morphology of the cracks, and discussed the rationality of finishing die and finishing process. The results show that the unreasonable design of finishing die is the main reason for the surface crack of bearing pedestal. After the optimization design of finishing die, the test results show that all indexes of the product meet the requirements, the improvement effect is obvious. 2021 Vol. 31 (04): 100-104 [Abstract] ( 6 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 105 Study on impregnated teeth for bits in extremely hard rock formation of oil and gas drilling Hot! XU Liang，LIU Yibo，SUN Yanlong，ZHOU Jinhui DOI: 10.13228/j.boyuan.issn1006-6543.20190226 This paper introduces the raw material and structure design of impregnated teeth used for drilling bits in extremely hard rock at oil and gas exploitation, and emphatically introduces the key technology of impregnated teeth preparation, which are the Diamond "encapsulated ball" technology and HIP process treatment technology. The influence of HIP process on the density and wear resistance of impregnated teeth is verified by indoor grinding test and 6 inch impregnated bits are prepared and test on drilling platforms. The average drilling speed of the impregnated bits in Grade 10 hardness granite can reach 2.7 m/h under the pressure of 6.7 t and rotary speed of 140 r/min. 2021 Vol. 31 (04): 105-109 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 110 Analysis on discontinuous display of ultrasonic flaw detection of molybdenum infiltrated copper connecting plate for gas rudder Hot! GUO Yingli，QIU Xiangru，SHENG Xi，HUANG Xin，LIN Bingtao，SUN Xiaoxia DOI: 10.13228/j.boyuan.issn1006-6543.20200158 Taking molybdenum infiltrated copper (Mo-10Cu) connecting plate used in gas rudder system as the research object, the discontinuous display phenomenon found in ultrasonic flaw detection of products was analyzed. The results show that there are micropores with a diameter of about 2~5 μm in the banded area (discontinuous display area) marked by ultrasonic flaw detection of molybdenum infiltrated copper products, which is the root cause of discontinuous display of ultrasonic flaw detection. The banded region and the non-banded region have almost the same microstructure and similar mechanical properties. Suggestions on classification of ultrasonic flaw detection for molybdenum infiltrated copper products are put forward. 2021 Vol. 31 (04): 110-116 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 1 )

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