Home  |  About Journal  |  Editorial Board  |  Instruction  |  Subscribe  |  Advertisement  |  council  |  Contact Us  |  中文

Forthcoming Articles       Current Issue       Advanced Search       Archive       Download Articles       Read Articles       Email Alert

Quick Search     Adv Search   2023 Vol. 33, No. 03 Published: 2023-06-10   1 Research progress on fine metal powder materials for electronic paste Hot! LIU Xiangqing，SUN Haixia，JIANG Zhi，ZHANG Xu，ZHANG Bin，WANG Jianwei，HE Huijun，WANG Limin DOI: 10.13228/j.boyuan.issn1006-6543.20230078 Electronic paste is the fundamental material of IT industry, widely used in aviation, aerospace, IT, com‐ munication device, automobile industry and many other fields. With the rapid and high integrated development of IT industry, as a conductive phase metal powder materials require high purity, controllable shape, free-agglomera‐ tion, controllable size and narrow distribution, and low oxygen content. This paper summarizes the main uses of electronic paste and analyses the preparation methods of fine metal powder materials. It is suggested the prepara‐ tion technology, development direction and applications of spherical and flake fine metal powder materials 2023 Vol. 33 (03): 1-6 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 7 Regression analysis for tensile strength of powder metallurgy low alloy steels Hot! FU Jiaqian，YU Yongliang，ZHANG Dejin，LI Songlin DOI: 10.13228/j.boy Powder metallurgy low alloy steels are an important component of iron-based powder metallurgy mate‐ rials, which are widely used in structural components. With the development of the powder metallurgy industry towards high-density, high-strength and complex-shaped powder metallurgy products, higher demands have been placed on the mechanical properties. The influence of chemical composition and related manufacturing process parameters on the mechanical properties of powder metallurgy low alloy steels is still unclear. The purpose of this study is to investigate the influence of various factors on the mechanical properties of powder metallurgy low alloy steel, to obtain a relationship model between chemical composition and manufacturing process parameters and the tensile strength, and to achieve effective prediction of material properties. Fe-Ni-Cu-C powder metallurgy low al‐ loy steels with LAP100.29 water-atomised iron powder as the base powder were prepared after pressing and sinter‐ ing, tensile strength was tested and a tensile strength database was established. A multiple linear regression model was established for the tensile strength of the powder metallurgy low alloy steels with pressing pressure, carbon content, nickel content, copper content and iron powder purity as independent variables. The regression model was tested for significance to determine the validity of the model and the performance of the regression model was as‐ sessed by the coefficient of determination and the mean relative error. Specimens of Fe-1Ni-1Cu-0.3C, Fe-1Ni- 1Cu-0.5C and Fe-1Ni-1Cu-0.8C powder metallurgy low-alloy steels were prepared under the same experimental conditions for tensile strength testing and metallographic observation to validate the multiple regression model. The multiple linear regression model for tensile strength is TS=-334 652.22+0.34 P+165.96 C+12.76 Ni+32.42 Cu+ 3 358.06 Fe. Significance tests show that the linearity of the model is significant and that the linear relationships between each of the variables in the model and tensile strength are significant. The R2 of the model was 0.873 and the R 2 adj was 0.863, indicating a good fit of the model. The mean relative error of the predicted values of tensile strength values is 6.39%. The mean relative error between the predicted and experimental values of the validation system is 4.43%, which is less different from the mean relative error value of the regression model. The multiple linear regression model has a good fit and high prediction accuracy, which can be used to effectively predict the tensile strength of powder metallurgy low alloy steels. More influencing factors present in the powder metallur‐ gy process can be taken into account to improve the mechanical properties database and establish a multivariate mechanical properties model.Applying it to actual production can reduce the number of experiments and tests, pro‐ viding a practical and effective solution to the problems of long product development cycles, low efficiency and high cost. 2023 Vol. 33 (03): 7-12 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 7 ) 13 Manufacturing of high nitrogen stainless steel by Selective Laser Melting with overmixed powders Hot! REN Jianbiao，ZHAO Dingguo，SUN Xin，WANG Shuhuan，NI Guolong，LIU Kun DOI: 10.13228/j.boyuan.issn1006-6543.20220118 Nitrogen evolution exists in the process of Selective Laser Melting of high nitrogen stainless steel pow‐ der under atmospheric pressure, and qualified high nitrogen stainless steel cannot be effectively made. Stainless steel powder with nitrogen content of 1.472% was prepared by overmixing powder method, and the printing form‐ ing experiment of overmixed powders were carried out on Selective Laser Melting equipment. The effect of laser processing parameters on the nitrogen content, microstructure and mechanical properties of high nitrogen stainless steel was studied. The experimental results show that high nitrogen stainless steel with more than 0.9% nitrogen content and certain mechanical properties can be prepared by overmixed powders method. The nitrogen content of the formed sample is inversely proportional to the laser power, at a scan speed of 1 000 mm/s, laser power is increased from 200 W to 300 W, nitrogen content decreases from 0.991% to 0.956%. Being directly proportional to the scan speed, at 225 W laser power, Scan speed is increased from 700 mm/s to 1 000 mm/s, nitrogen content increases from 0.823% to 0.985%. At 250 W laser power, Scan speed is increased from 700 mm/s to 1 000 mm/s, nitrogen content is increased from 0.817% to 0.970%. The scanning speed has more significant effects on the nitro‐ gen content. At a scan speed of 1 000 mm/s, ranging from 200 to 300 W, with the increase of laser power, the inter‐ nal defects of the sample gradually reduce, the forming quality becomes better, and the tensile strength increases first and then decreases. The optimization results show that the scanning speed of 1 000 mm/s and laser power of 275 W are the optimal parameters. The forming quality of high nitrogen stainless steel is the best, the number of internal defects is the least, and the comprehensive tensile properties are good, the tensile strength and yield strength are 1 001.7 MPa and 363.8 MPa, respectively, while the nitrogen content is higher than 0.9%. 2023 Vol. 33 (03): 13-22 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 23 Effect of sphericity on soft magnetic properties of FeSiCr alloy powders Hot! Lü Shiya，MA Hongqiu，KUANG Chunjiang，MENG Lingbing，ZHAO Gang，CUI Lei DOI: 10.13228/j.boyuan.issn1006-6543.20230026 The high spherical FeSiCr soft magnetic alloy powder was prepared by the improved combined atomiza‐ tion technology, and the D50 is 10 μm、12.5 μm、15 μm and 21 μm sample. At the same time, FeSiCr soft magnetic alloy powder with the same D50 particle size was prepared by conventional combined atomization technology as the control group. The morphologies of the two process powders were measured and observed by means of specific sur‐ face and pore size analyzer and scanning electron microscope, and the magnetic properties of FeSiCr soft magnetic powder were characterized by soft magnetic AC equipment. The results show that the morphology of the new com‐ bined atomized FeSiCr alloy powder tends to be spherical obviously, and the specific surface area of the powder with the same particle size is significantly lower than that of the conventional combined atomized powder. Both at‐ omization processes produce bcc structure α-Fe(Cr, Si) solid solution powder. Effective permeability of new com‐ bined atomized powder with the same particle size μe is lower than the conventional combined atomization powder, while the DC bias characteristic and magnetic loss are better than the conventional atomization, and the Pcv of X10 at 100 kHz and 50 mT is only 601.8 mW/cm3. 2023 Vol. 33 (03): 23-29 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 30 Effects of densification process on microstructure and properties of PM 6061 Al alloy Hot! YANG Mengxiang，HUANG Pengpeng，SHI Siyang，WANG Jiaojiao，WU Yake，JIANG Feng DOI: 10.13228/j.boyuan.issn1006-6543.20220124 Aluminum alloy parts prepared by traditional powder metallurgy pressing and sintering process can ful‐ ly play the advantages of nearly net forming and lightweight. It will gradually replace some die-casting and ma‐ chined parts in automobile, electrical appliances and other industries, which is of great significance for energy con‐ servation and emission reduction. 6061 Al alloy was prepared by powder metallurgy technology, and the effects of compaction pressure（140~330 MPa）and sintering temperature（566~616 ℃）on material density, microstruc‐ ture, dimensional change rate and properties were studied in this paper. In addition, T6 heat treatment was per‐ formed to improve mechanical properties of 6061 Al alloy. The results show that with the increase of compaction pressure, the density and hardness of the sintered samples increase first and then decrease, the dimensional change rate gradually decreases, and the tensile strength and electrical conductivity are improved continuously, but all the indexes above are improved with the increase of sintering temperature. The improvement of compaction pressure will gradually reduce the pores in the alloy substrate, increasing the sintering temperature can produce more lowmelting-point liquid phase filling pores to promote alloy density. In general, the comprehensive performance of the sample pressed at 210 MPa and sintered at 616 ℃ are potential, with the density of 2.597 g/cm3, hardness of 38.4HV, tensile strength of 139 MPa and stable dimensional shrinkage rate of 1.6 %. Further, the sintered sample is subjected to T6 heat treatment. After heat treatment, the hardness of the sample increases by 186 % to 109HV, the tensile strength increases by 95% to 271 MPa, and the elongation after fracture decrease from 11.9 % to 2.2 % . This research can provide useful reference for the industrial development and application of powder metallurgy 6061Al alloy 2023 Vol. 33 (03): 30-37 [Abstract] ( 4 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 38 Microstructure and properties of fine-grained pure Ti materials for golf heads Hot! YANG Hong，ZHANG Haolin，ZHOU Zheng DOI: 10.13228/j.boyuan.issn1006-6543.20220128 The high-strength face of the golf head is very significant, and the high-performance ball head material can ensure good control and forgiveness, higher hitting accuracy and longer hitting distance. In this paper, the finegrained pure Ti materials were fabricated by high-energy ball milling, cold compaction, vacuum sintering and hot extrusion, and the microstructure and properties of as-unextruded and as-extruded fine-grained pure Ti were sys‐ tematically studied by scanning electron microscope（SEM）and tensile testing machine. The results show that the spherical Ti powders are transformed into fine nano-crushed particles after high-energy ball milling for 5 hours, and the average particle size is reduced from 25 μm to less than 5 μm and the dispersion is uniform. The microstruc‐ ture and grains of as-extruded fine-grained pure Ti are adequately refined and the micro-void defects in the grains disappeare. In addition, the tensile strength, yield strength and elongation of the as-extruded fine-grained pure Ti are increased by about 16.1%, 19.7% and 16.3% compared with the as-unextruded. The fracture morphology shows that compared with before extrusion, the number of fracture dimples of the as-extruded fine-grained pure Ti is more, and the depth is small and uniform, and the distribution of tearing edges is more dense. 2023 Vol. 33 (03): 38-43 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 44 Preparation of plasma-sprayed 8YSZ thermal barrier coatings under orthogonal test design Hot! YU Haiyuan，BIAN Qing，XUE Zhaolu DOI: 10.13228/j.boyuan.issn1006-6543.20220110 In order to explore the coupling effect of spraying process parameters on microstructure and mechanical properties of coating, 8YSZ thermal barrier coating was prepared by atmospheric plasma spraying technology. The results show that the plasma-sprayed 8YSZ coating is layered with fine columnar crystal structure between layers. The coating is composed of t-ZrO2 and a small amount of m-ZrO2 phase. The change of spraying parameters has no obvious effect on the phase composition. The comprehensive effect of spraying parameters on bonding strength and porosity of thermal barrier coatings is in the order of spraying distance > power > main gas flow. The average bond‐ ing strength and porosity of 8YSZ thermal barrier coatings are 18 MPa and 11.14% with the best spraying process parameters optimized by orthogonal experiment, among which spraying distance is 110 mm, power is 30 kW and main gas flow is 45 L/min. 2023 Vol. 33 (03): 44-52 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 53 Preparation of Mn2AlB2 by Combustion reaction Hot! HAN Jingxian，LIU Jialin DOI: 10.13228/j.boyuan.issn1006-6543.20210149 Mn/Al/B element mixed powders were used as raw material for combustion reaction to synthesize Mn 2AlB2 material with high content. The synthesis of Mn2AlB2 by combustion reaction in tubular furnace or spark plasma sintering furnace was systematically studied, and the reaction mechanism of combustion reaction synthesis of Mn 2AlB2 was put forward. The results show that in the products of combustion reaction in tubular furnace, the main phases are Mn2AlB2 and MnB, and contain a small amount of Mn2B, Al and AlMnx. Increasing Al content in raw materials will significantly promote the synthesis of Mn2AlB2. The combustion reaction of Mn/Al/B system be‐ longs to thermal explosion mode, and the heat release of the reaction is low. The sintering activity of the product is poor and easy to crush. The sample is composed of a large number of Mn2AlB2 lath or massive grains at the level of several microns and many grains of other phases at the level of submicron. Finally, a reaction mechanism of Mn 2AlB2 by combustion synthesis reaction is proposed. 2023 Vol. 33 (03): 53-58 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 59 Preparation of high chromium cast iron-Al2O3-TiC surface composites by pressureless infiltration Hot! SHI Yongliang，CAO Lei，CHEN Cunguang，YANG Fang DOI: 10.13228/j.boyuan.issn1006-6543.20230077 High chromium cast iron matrix Al2O3-TiC surface composites with a thickness of 3~4 mm were pre‐ pared on the surface of high chromium cast iron by pressureless infiltration of Ti-Al2O3 preform. The microstruc‐ ture and phase composition of the surface composites were analyzed by SEM, EDS and XRD, and the wear resis‐ tance and thermal shock resistance of the surface composites were measured. The results show that the liquid metal can be quickly induced to permeate the preform through Ti-C reaction with the adding of Ti element to the preform. In the infiltration layer, Al2O3 particles are tightly combined with the matrix and evenly distribute without cracks and defects. At high temperature, the transition layer around Al2O3 particles is formed by dissolution and precipita‐ tion of TiC, and the bonding strength between Al2O3 particles and matrix is improved. The wear resistance of the in‐ filtrated layer is 3~4 times that of high chromium cast iron, also it can resist 15 thermal shocks without cracks at 800 ℃. 2023 Vol. 33 (03): 59-64 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 65 Study on high temperature oxidation resistance and microwave absorption properties of Ti3SiC2 powders Hot! GUO Yang，TAN Kehua，GUO Xiaoying，WANG Bing，LI Huirong，BI Lei DOI: 10.13228/j.boyuan.issn1006-6543.20220117 Ti 3SiC2（TSC）is of great interest in the area of high-temperature microwave absorption because of its good electrical conductivity and high thermostability. In this paper, TSC powders were prepared by high-tempera‐ ture solid-state reaction at 1 400 oC for 3 h. The experimental raw materials were Ti powder, Si powder and graph‐ ite powder. Its composition and phase were analyzed by XRD and XPS. Further, its high temperature oxidation resistance and microwave absorption properties were characterized by thermogravimetric analyzer and vector net‐ work analyzer. The results show that the impurity phases in TSC powders mainly include SiC, SiO2, TiO2 and TiC. TSC powders can maintain good high-temperature oxidation resistance below 400 oC. When the thickness of the mixture of TSC and paraffin is 2.0 mm, the effective absorption bandwidth（EAB）of the composite containing 60%（mass fraction）TSC is 0.9 GHz（17.10-18.0 GHz）. When the TSC content is increased to 70%, the EAB is expanded to 3.86 GHz（12.95-16.81 GHz）. When the TSC content is further increased to 80%, its EAB decreases to 1.44 GHz（9.37-10.77 GHz）. 2023 Vol. 33 (03): 65-70 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 71 Effect of sintering temperature on properties of iron-based powder sintered products Hot! SU Fengge，SHANG Shubo，ZHANG Ruiping，ZHENG Zhuo，SHANG Yanjing DOI: 10.13228/j.boyuan.issn1006-6543.20220101 In this paper, Fe-Cu-C, Fe-Cu-Ni-Mo-C and Fe-Mo-C green were sintered at five different tempera‐ tures of 1 100, 1 140, 1 180, 1 200 and 1 220 ℃ in a powder metallurgy industrial furnace. The metallographic and fracture morphology were observed by metallographic microscope and scanning electron microscope（SEM）. The effects of different sintering temperatures on the hardness, fracture strength, metallography and fracture mor‐ phology of the samples were studied. The experimental results show that temperature at 1 100 ℃ and 1 140 ℃ have little influence on the hardness and strength of the above alloy between 1 100 ℃ and 1 220 ℃, the fracture strength of Fe-Mo-C and Fe-Cu-Ni-C increases with the increase of sintering temperature. When the sintering temperature exceeds 1 180 ℃, the fracture strength of Fe-Cu-C materials decreases with the increase of sintering temperature. 2023 Vol. 33 (03): 71-76 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 7 ) 77 Characterization of carbides in powder high-speed steel based on digital image processing Hot! SHI Hui，WU Binhan，LU Yuhua，YU Xing，ZHU Yifei，ZHANG Songchuang，WAN Weihao DOI: 10.13228/j.boyuan.issn1006-6543.20220103 Aiming at the problems of characterization of small, numerous and complicated carbides in powder met‐ allurgy high speed steel, based on the high-throughput field emission scanning electron microscope，a quantitative characterization method of carbides in powder metallurgy high speed steel was established by means of digital im‐ age processing. By filtering, double threshold segmentation, feature extraction, expansion, corrosion and skeleton extraction on a large number of SEM images, the method can quickly obtain the quantitative statistical distribution information of carbides in SEM images. It has been applied to the quantitative analysis of the size, quantity and dis‐ tribution of MC, M6C type carbides of AHPT15M in different states. The results show that the carbide size distribu‐ tion of AHPT15M is 0-5 μm, and the carbide size below 2 μm accounts for more than 95% of the total carbide. The area fraction of carbide area in annealed speed steel is 21.62%, of which the proportion of MC type carbide is 14.05%, and that of M6C type carbide is 7.57%. After heat treatment, the area fraction of carbide decreases to 15.05%, of which the MC carbide is 10.47%, and that the M6C carbide is 4.58%. The quantitative result of carbides obtained by this method is consistent with the statistical data of physicochemical phase analysis. It shows that this method can quickly identify carbides of a large number of images in powder metallurgy high speed steel, and the results are more comprehensive. 2023 Vol. 33 (03): 77-82 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 83 Effect of carbon nanotubes on porous TiC-TiB2 composites synthesized by reaction sintering Hot! ZHANG Xu，CHEN Jingjing，ZHANG Jinling DOI: 10.13228/j.boyuan.issn1006-6543.20210154 TiC-TiB 2 composites were produced by reaction sintering. The effects of carbon nanotubes addition on the microstructure and mechanical properties of ceramic matrix composites were studied by X-ray diffractometry （XRD）, scanning electron microscopy（SEM）, Electro-Probe Microanalyzer（EPMA）and high resolution scan‐ ning electron microscopy（HRSEM）. The results show that the phases of the products are composed of TiC, TiB, Ti 3B4, TiB2, large number of open and closed pores exists on the matrix simultaneously. Compared with the base mi‐ crostructure of matrix without CNTs addition, the grains of the cermets with CNTs addition are refined due to con‐ straining the grain growth. Meanwhile some CNTs exist among the coming out of bulk and pull them together. TiC synthesized by CNTs and Ti connects into a network structure and increases the compressive strength, but it will decrease when the content of CNTs is excessive. 2023 Vol. 33 (03): 83-88 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 89 Effect of cold upsetting process on mechanical properties of Al-TiO2-Gr powder metallurgy composites Hot! Lü Ganglei，ZHU Yonggang，ZHANG Zhihui DOI: 10.13228/j.boyuan.issn1006-6543.20220054 Using ball mill powder as raw material, Al+2.5%TiO2+2%Gr, Al+2.5%TiO2+4%Gr, Al+5.0%TiO2+ 2%Gr, Al+5.0%TiO2+4%Gr aluminum-based composite materials were prepared by powder metallurgy method. The compaction process was carried out in a 40 kN hydraulic press with a suitable punch and die, and then sintered in an electric furnace. The sintered preform was subjected to an incremental compressive load of 10 kN until cracks were found on the free surface. During the cold heading process, the composite material produced elongated grains due to deformation. The upsetting process reduces the porosity in sintered samples. For the composites containing 2.5% TiO 2 and 2% graphite, the pores are closed and filled by reinforcements, and the number of pores after cold upsetting is very small. The addition of TiO2 and graphite particles improves the strength and hardness of the com‐ posites. For the composites containing 5% TiO2 and 2% graphite particles, the maximum hardness value 36.14HRB is obtained. 2023 Vol. 33 (03): 89-95 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 96 Research on the filtration performance of sintered metal filter tube and the mechanism of back-blowing ash cleaning Hot! ZHANG Lifeng，YOU Chao，GUO Qi，LI Fangxia，LI Caixia，NAN Haijuan DOI: 10.13228/j.boyuan.issn1006-6543.20220126 Sintered metal filter tube is the core element in the high-temperature gas filter, whose filtration perfor‐ mance is directly related to the downstream safety production. In this paper, through the analysis of the circulating pressure drop of the sintered metal filter tube, the dynamic pressure change inside the sintered metal filter tube dur‐ ing the pulse-back process, changes in the thickness of the dust cake, the shedding of the dust cake and the outlet concentration, it is found that the sintered metal filter tube has the better filtration performance, the concentration of particles is less than 10 mg/m3, the particle size distribution is basically below 1 μm, which meets the filtration requirements. The dynamic pressure change inside the filter tube is consistent with the trend of the thickness of the dust cake changing with time. When the dynamic pressure inside the filter tube reaches the maximum, the dust cake is also fluffy to the maximum. The cycle performance regeneration function of the sintered metal filter tube could be completed by using a low pulse-back pressure combined with the dynamic pressure change inside the fil‐ ter tube, thickness of the dust cake and the shedding of the external dust cake. 2023 Vol. 33 (03): 96-100 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 101 Effect of BCP surface treatment on the properties of superconducting niobium materials Hot! BAO Xifang，XIE Yongxu，WANG Huihui DOI: 10.13228/j.boyuan.issn1006-6543.20220097 The superconducting niobium high RF cavity, as the core component of the X-ray free electron laser de‐ vice linear accelerator, works at 2.0K to accelerate the electrons to the desired energy. The accelerated cavity of the superconducting high RF cavity is made of high purity niobium material. After this niobium material is electron beam melting, forging, rolling, vacuum annealing and BCP chemical polishing treatment, the performance meets the requirements of superconducting high RF cavity, and the high purity niobium materia is processed by deep stamping and electron beam welding. High purity niobium material has high residual resistance ratio RRR value and excellent mechanical properties, but also requires niobium material to have good surface quality, Therefore, the selection of the appropriate BCP chemical surface treatment method is an important research content in the process of preparing high quality superconducting niobium material. 2023 Vol. 33 (03): 101-106 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 107 A study on quenching cracking behavior in a nickel-based P/M superalloy ring-shaped worked piece Hot! LI Kemin，WANG Yixing，LIN Xinan，LI Yang，LIU Jiantao，LIU Mingdong DOI: 10.13228/j.boyuan.issn1006-6543.20220208 ：According to the cracking behavior of FGH4095 alloy ring part in the process of heat treatment quench‐ ing, the quench cracking mechanism was clarified based on the metallographic analysis of the microstructure of the cracking fracture, combined with the numerical simulation of the stress field and temperature field in the quenching process, and the effective measures to solve the quench cracking were given. It is concluded that the dynamic embrittlement occurs in the grain boundary of FGH4095 ring part during quenching under the combined action of tensile stress and oxidation, leading to the cracking along the circumferential direction, and the fracture presents typical intergranular embrittlement characteristics. The quenching cracking can be eliminated by coating the sur‐ face of the ring part with antioxidant coating before heat treatment. 2023 Vol. 33 (03): 107-110 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 111 Heat-treatment process control for microstructure and properties of laser cladding WC@Ni/Ni60 coating Hot! MEI Mingliang，HUANG Xu，LIU Chang DOI: 10.13228/j.boyuan.issn1006-6543.20230060 The heat treatment process is important to improve the forming quality of laser cladding coatings. In this paper WC@Ni / Ni60A and rare earth mixed powder were used to investigate the influence of different heat treatment processes on the microhardness, microstructure, phase composition, and residual stress of the cladding layer and to explore the optimal annealing temperature. The results show that increasing heat treatment temperature decreases the coating microhardness. Higher microhardness of the coating can be obtained at 700 ℃. Samples with 1% La 2O3 and with 0.5% Y2O3 have a hardness of 64.9HRC and 65.3HRC, respectively. With the increase of heat treatment temperature, the wear volume becomes larger. At an annealing temperature of 700 ℃, the friction coeffi‐ cient of the sample is lower than that of the untreated one. The increase in heat treatment temperature helps to re‐ duce the residual stress. Considering the performance indexes, the optimal heat treatment scheme includes the fol‐ lowing parameters: the heating temperature is 700 ℃, the heating speed is 10 ℃/min, the insulation time is 60 min, and cooling mode is furnace cooling. The results provide a theoretical basis for improving coating quality through heat treatment. 2023 Vol. 33 (03): 111-119 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 120 Effect of hot isostatic pressing on mechanical properties of 3D printed metal components Hot! LIN Yizhen，LIU Wenbin DOI: 10.13228/j.boyuan.issn1006-6543.20220135 Hot isostatic pressing can eliminate internal defects and residual stress of materials and improve me‐ chanical properties. As an important means of post-treatment for metal 3D printed components, it has attracted more and more attention and developed rapidly at home and abroad. The recent progress in improving mechanical properties of 3D printed components by hot isostatic pressing is reviewed, the main reasons for the improvement of mechanical properties are described, and some suggestions for hot isostatic pressing 3D printed components are put forward. 2023 Vol. 33 (03): 120-124 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 125 Study on improving reducibility of iron concentrate powder by adding coal Hot! LI Yalong，LIU Weidong，MA Chunyuan DOI: 10.13228/j.boyuan.issn1006-6543.20210181 With the gradual tightening of environmental protection and energy-saving policies in recent years, the structure of blast furnace burden has undergone significant changes, mainly due to the significant difference in met‐ allurgical properties between pellets and sintered ore, which has had a certain impact on the stability and economic and technical indicators of blast furnaces. The ratio of iron concentrate powder and coal powder, as well as the reduction degree achieved by iron concentrate powder under different atmospheres and temperatures were investi‐ gated. The results show that under the same reduction temperature and atmosphere, the reduction degree and metal‐ lization rate of the iron concentrate powder mixed with coal particles increase with the increase of coal content. This indicates that the C content in coal has a significant impact on the reduction degree of iron concentrate pow‐ der. When the coal content is 15%, the reduction degree of the reduced sample increases. The metallization rate reaches over 97%, and the continued addition of coal powder has no significant impact on the results. The Fe2+ con‐ tent of the reduced sample decreases with the increase of coal content. When the reduction atmosphere and coal content are the same, the reduction temperature is different, the reduction degree and metallization rate increase with the increase of temperature. The reduction degree tests at 900 ℃ is below 97%. When the reduction tempera‐ ture and coal content are the same, the reduction degree and metallization rate increase with the increase of CO concentration. After reduction, holes and pits appear on the surface of the sample, forming a dense iron layer with co‐ lumnar iron whiskers. The main component of the sample is C, which may be due to the coal powder falling off from the iron ore powder during the high-temperature reduction process, and the combination is not tight enough. The experiment provides accurate data such as reduction temperature, reduction atmosphere, and coal blending amount for the actual production process, which can save energy and reduce costs. 2023 Vol. 33 (03): 125-132 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 )

Copyright © Editorial Board of Powder Metallurgy Industry Supported by:Beijing Magtech