球形TC4合金粉末的制备、表征及雾化机理

采用真空气体雾化法制备了TC4合金粉末,并采用激光粒度分析仪、扫描电子显微镜和霍尔流速计等对制备的粉末粒度分布、组织形貌、松装密度、流动性等进行了测试分析。结果表明:真空气体雾化法制备的TC4合金粉末粒度呈正态分布,尺寸集中分布在32.52～182.50μm左右,粉末中值粒径d_(50)为92.70μm,粉末球形度高,氧含量低(0.14%);粉末具有较低的松装密度和良好的流动性,粒径在38～106μm的粉末其流动性为25～50 s/(50 g),松装密度为2.52～2.56 g/cm~3。TC4合金粉末中粒径较大的颗粒表面呈发达的近似等轴的胞状枝晶组织,而颗粒粒径越小,其表面越光滑。少部分小颗粒粘附在大颗粒表面上,出现连体的"卫星"状。     

超瞬态凝固增材制造梯度整体涡轮叶盘用高温合金粉末特性研究I：盘体用合金粉末

本文针对超瞬态凝固增材制造梯度整体涡轮叶盘用高温合金粉末特性开展研究。根据合金的承温能力和JMatPro相平衡计算结果,分别选用GH4169和K418作为盘体心部和轮盘边缘部位材料,DZ4125作为叶片材料。采用真空感应熔炼氩气雾化制粉(VIGA)制备高温合金粉末,筛分至53-105μm粒度范围,采用差示扫描量热分析（DSC）、场发射扫描电镜（FESEM）、电子探针（EPMA）、激光粒度仪、动态图像粒度粒形分析仪以及综合粉体性能测试仪对高温合金粉末的相变温度、显微组织、元素偏析行为、粒度、粒形、松装密度、振实密度和流动性进行了系统表征。结果表明：K418合金固液温度范围比G4169合金窄,K418合金的γ′和MC碳化物的开始析出温度均比GH4169高,过渡区(GH4169+K418)混合成分合金主要强化相的析出温度介于GH4169和K418两种合金之间。GH4169和K418合金粉末形貌主要为球形和近球形。表面和截面显微组织主要呈树枝晶结构,所含元素中偏析倾向较强的元素有Ti、Nb、Zr和Mo,均富集分布于枝晶间,而偏析倾向弱的元素包括Ni、Cr、Fe和Al,高温合金粉末元素偏析类型与铸造镍基高温合金相近,但粉末组织更为细小均匀。激光衍射和动态图像分析法测得的粉末粒度值接近,GH4169的D50分别为79.1μm和76.2μm,K418的D50分别为67.8μm和65.6μm。动态图像法测得2种合金均具有较好的球形度,GH4169和K418的SPHT均值分别为0.91和0.90。所选GH4169和K418高温合金粉末具有相近的松装密度、振实密度和流动性,其松装和振实密度分别达到合金理论密度的50%和60%,压缩度在13.3~15.5%范围,粉末具有较好的流动性（18.5~20.4 s?(50 g)-1）。     

超瞬态凝固增材制造梯度整体涡轮叶盘用高温合金粉末特性研究Ⅱ：叶片用合金粉末

本文针对超瞬态凝固增材制造梯度整体涡轮叶盘高温合金叶片用合金粉末特性开展研究。根据合金的承温能力和JMatPro相平衡计算结果,选用DZ4125作为叶片材料,K418作为叶盘轮缘部位材料。采用真空感应熔炼氩气雾化制粉(VIGA)制备DZ4125高温合金粉末,筛分至53-105μm粒度范围,采用采用差示扫描量热分析（DSC）、场发射扫描电镜（FESEM）和能谱（EDS）、激光粒度仪、动态图像粒度粒形分析仪以及综合粉体性能测试仪对DZ4125高温合金粉末的相变温度、显微组织、析出相成分、元素偏析行为、粒度、粒形、松装密度、振实密度和流动性进行系统表征。结果表明：DZ4125比K418合金的固液凝固温度范围宽,过渡区DZ4125+K418混合成分合金其液相线温度和MC碳化物开始析出温度介于两种合金之间,γ′开始析出温度与两种合金相当。DZ4125合金粉末形貌主要为球形和近球形,表面和截面显微组织主要呈树枝晶结构。所含元素中偏析倾向较强的元素有Hf、Ta、Ti、Mo和W,而偏析倾向弱的元素包括Ni、Co、Cr和Al。粉末内部枝晶间区分布有细小的MC碳化物,尺寸约为200nm。激光衍射和动态图像分析法测得的DZ4125粉末粒度值接近,中位径D50分别为70.2μm和72.8μm。动态图像法测得DZ4125合金粉末具有较好的球形度,SPHT和b/l均值分别为0.91和0.86。所选DZ4125高温合金粉末具有较好的松装密度、振实密度和流动性,其松装和振实密度分别达到合金理论密度的52%和63%,压缩度为17.7%,且粉末具有较好的流动性（20.79 s?(50 g)-1）。     

直流电弧热等离子体球化处理TA1粉末工艺研究

采用直流电弧热等离子体对不规则TA1粉末进行球化处理。利用金相显微镜、扫描电子显微镜、粒度粒形分析仪、霍尔流速计、斯科特容量计及氧氮分析仪等分析测试手段,研究球化工艺对粉末组织形貌、粒度分布、球形度、流动性、松装密度及氧含量的影响。结果表明,球化处理可将不规则形状TA1粉末球化为表面附着亚微米颗粒的实心球形;球形粉末内部组织由等轴状α相转变为长条状α相。球化处理使TA1粉末平均粒径和氧含量降低,球形度升高。原料粉末粒度越小、等离子体发生器功率越高,球化后粉末平均粒径越小,球形度越高;但会导致球化后粉末中亚微米颗粒含量增加、粉末流动性变差、松装密度降低;去除亚微米颗粒可以提高粉末流动性,并进一步降低氧含量。     

射频等离子体制备球形钨粉的研究

通过射频等离子体球化处理工艺,以不规则形状钨粉为原料,制备了球形钨粉,并研究了加料速率和粉末粒度对粉末球化率的影响。采用扫描电子显微镜、X射线衍射和激光粒度分析仪对球化处理前后粉末的形貌、物相和粒度分布进行了测试和分析。结果表明：粒度在5.5~26.5 μm范围的不规则形状钨粉,经等离子球化处理后得到表面光滑、分散性好、球化率可达100%的球形钨粉。球化处理后,粉末的粒度略微增大。随加料速率的增加,钨粉的球化率降低。随着钨粉球化率的提高,粉末的松装密度和流动性得到显著改善。松装密度由6.80 g/cm3 提高到11.5 g/cm3,粉末流动性由14.12 s/50 g提高为6.95 s/50 g     

热喷涂Cr/Al2O3复合粉末的制备及性能研究

目的获得热喷涂用包覆型Cr/Al_2O_3复合粉末的制备工艺,探究工艺参数对热喷涂粉末结构及性能的影响规律。方法将纳米Al_2O_3水分散液与粘结剂混合润湿形成胶状液体,然后使其在核心粒子Cr表面团聚直接得到陶瓷相包覆金属相的复合颗粒,确定最佳制备工艺参数,并通过扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)和霍尔流速与松装密度计研究工艺参数对复合粉末结构和性能的影响。结果在核-壳结构复合粉末制备过程中,加入一定量的粘结剂和减少包覆次数可以改善包覆效果,最终制得的包覆型颗粒壳层厚度可以达到25μm。随着Cr含量的增大,包覆效果有所下降,但粉末流动性变好,松装密度值提高。初始Cr粒度增大,包覆效果增强,颗粒球形度改善,但流动性和松装密度变化不大。结论机械包覆Cr/Al_2O_3复合粉末的最佳制备工艺参数为加入质量分数为5%的粘结剂进行一次包覆,该方法制得的复合粉末粒度分布均匀,流动性和松装密度值良好,适合热喷涂。     

PH13-8Mo钢的离子渗氮工艺

对PH13-8Mo钢离子渗氮工艺参数进行了研究,其中包括渗氮温度、渗氮时间及渗氮件表面粗糙度。结果表明:随渗氮温度的升高、渗氮时间的延长、零件表面粗糙度的降低,PH13-8Mo钢渗氮层厚度增加;渗氮零件表面粗糙度对渗氮层脆性等级影响较大,渗氮零件表面粗糙度为6.3 μm时,其脆性等级达到III级;渗氮时间、渗氮温度及零件表面粗糙度对渗氮层硬度影响甚微。渗氮温度540 ℃,渗氮时间22 h,零件表面粗糙度0.8 μm时,PH13-8Mo钢可获得良好的渗氮层,渗氮层厚度可达197.5 μm,渗氮层硬度可达1083 HV0.2,脆性等级为II级。     

电渣重熔-等离子旋转电极雾化制备高品质316H奥氏体不锈钢粉末

首先采用电渣重熔法熔炼316H奥氏体不锈钢母合金,随后采用等离子旋转电极雾化(PREP)法制备了球形316H奥氏体不锈钢粉末.利用氧氮分析仪、扫描电镜(SEM)、X射线衍射仪(XRD)、霍尔流速计和激光粒度分布仪等研究了粉末的氧含量、形貌、相结构、流动性、松装密度、振实密度及粒度分布.结果表明:电渣重熔制备的316H奥氏体不锈钢母合金全氧含量为20×10-6,铸锭成分均匀;等离子旋转电极雾化法制备的316H奥氏体不锈钢粉末全氧含量为70×10-6,粉末粒度呈现双峰分布,细粉收得率高,粒径为15～150 μn的粉末占比近80％,粉末粒径分布范围广、球形度高、卫星粉少.粉末表面基本为胞状晶,截面为均匀的枝晶组织,为单一的γ-Fe相结构.制备态粉末的霍尔流速、松装密度和振实密度分别为14.83 s-50-1 g-1、4.725 g·cm-3和5.401 g·cm-3.粗粉和细粉质量分数各占一半时,粉末的霍尔流速为12.91 s·50-1g-1,小于初始粉末的霍尔流速,提高了粉末的流动性能.长时间的真空储存能降低粉末的带电性能,进而降低粉末颗粒之间排斥作用,可进一步提高粉末流动性.粗、细粉之比为7:3时,粉末的填充性能最好,填充率高达70.6％.     

球形钨粉的制备及应用

球形钨粉以其良好的流动性、高的松装密度和振实密度广泛应用于喷涂、增材制造等材料制备领域。本文以不规则形状钨粉颗粒为原料,采用射频等离子球化技术制备球形钨粉,并对球形钨粉进行铺粉及成形实验效果评价。在射频等离子球化过程中,研究球化工艺参数（送粉速率、送粉位置）和原料粉末形态对球化结果的影响。在铺粉实验方面,研究粉末特征和铺粉层厚对铺粉效果的影响。采用扫描电子显微镜、激光粒度分析仪和BT-100粉体综合特性测试仪对球化处理前后粉末的形貌、粒度、流动性、松装密度和振实密度进行测试和分析。结果表明：经过球化处理后,钨粉颗粒呈规则球形,表面光滑,球化率可达100%,流动性、松装密度和振实密度得到明显提高。球化率高的粉末流动性好,铺粉效果好;随着层厚的增加,铺粉效果逐渐得到改善;采用合适粒径的球形钨粉打印的钨薄壁件表面相对光洁,尺寸精度高。     

高温合金差示扫描量热分析(DSC)的影响因素研究II：粉末粒度和显微组织

对固溶强化型625镍基高温合金粉末进行升、降温差示扫描量热分析（DSC）试验,研究了<37μm、45-53μm、75-105μm、105-150μm、150-355μm不同粉末粒度对相变温度的影响。采用场发射扫描电镜（FESEM）、电子探针（EPMA）和同步辐射X射线衍射（SXRD）对625合金粉末的形貌、元素分布和相组成进行表征。结果表明：不同粒径PM625粉末均为树枝晶结构,枝晶间距在2~10μm范围,元素 Ni和Cr倾向分布于枝晶干,Mo和Nb偏析于枝晶间。不同粒度的PM625粉末中均仅存在基体γ相。PM625粉末DSC加热曲线固相线附近区域拐点尖锐,表现为合金开始熔化温度（偏离基线的拐点）与名义固相线温度（切线交点）差异很小,不同粒度间的差异仅为2-5℃。合金完全熔化后重新冷却的过程中原始粉末的低偏析特性消失,冷却曲线固相线区域圆弧较大,名义固相线和终凝温度差较大,为53-65℃。DSC试验升温过程中不同粒径粉末的固、液相线以及初熔温度最大差异分别为3℃、2℃和2℃,降温过程不同粒径粉末固、液相线温度差分别为6℃和2℃。0-355μm粉末粒径范围内,粒径对固溶强化型PM625高温合金粉末相变温度无明显影响。     

Effect of Particle Morphology and Size Distribution on Cold-Sprayed Pure Titanium Coatings

The effects of commercially pure titanium particle morphology (spherical, sponge, and irregular) and size distributions (mean particle sizes of 20-49 μm) on the cold spray process and resulting coating properties were investigated. Numerous powder and coating characterizations were performed including: powder oxygen and nitrogen contents, powder flowability, powder compressibility, coating microhardness, coating porosity, LOM/SEM analyses, and XRD. Compared to spherical powders, the sponge and irregular CP-Ti powders had higher oxygen content, poorer powder flowability, higher compression ratio, lower powder packing factor, and higher average particle impact velocities. XRD results showed no new phases present when comparing the various feedstock powders to corresponding coatings. A higher particle temperature was also obtained with larger particle size for all feedstock powder morphologies processed with the same set of spray parameters. A spherical powder with 29 μm mean particle size was found to have the lowest porosity coating and best cold sprayability. The relationships of several as-cold sprayed coating characteristics to the ratio of particle impact and critical velocities were also discussed.     

Effects of Oxygen Increasing/Decreasing Processes on Surface Characteristics of Superalloy Powders and Properties of Their Bulk Alloy Counterparts: Powders Storage and DegassingEI北大核心CSCD

采用场发射扫描电镜(FESEM)、X射线光电子谱(XPS)、高角环形暗场扫描透射电镜(HAADF-STEM)以及程序升温脱附与质谱联用(TPD-MS)等表征手段研究了不同窄粒度范围镍基高温合金粉末的原始表面状态以及存储和脱气等增/降氧过程对合金组织和性能的影响。结果表明：不同粒度原始态粉末的表面组成均为Ni O/Ni(OH)₂、TiO₂、CoO和Cr₂O₃,0～15μm粒径粉末(细粉)和150～180μm粒径粉末(粗粉)平均氧化膜厚度分别为3.32和10.90 nm。细粉和粗粉在空气环境中存储后氧含量逐渐增大，在3～10 d达到稳定值，分别约为250×10^-6和40×10^-6。存储后0～53μm粉末制备的块体合金氧含量升高，室温、650℃和750℃拉伸强度变化不大，但塑性下降，合金在650℃、890 MPa和750℃、530 MPa的持久性能均下降。0～15μm细粉加热过程中(室温～1000℃)会发生气体脱附，存在明显脱附峰的气体包括CO₂     

Plasma spraying of combustion flame spheroidized hydroxyapatite (HA) powders

Tailoring powder characteristics to suit the plasma spray process can alleviate difficulties associated with the preparation of hydroxyapatite (HA) coatings. Commercial HA feedstock normally exhibit an angular morphology and a wide particle size range that present difficulties in powder transport from the powder hopper to the plasma spray gun and in nonuniform melting of the powders in the plasma flame. Hence, combustion flame spheroidized hydroxyapatite (SHA) was used as the feedstock for plasma spraying. Spherical particles within a narrow particle size range are found to be more effective for the plasma spray processes. Results show coatings generated from spheroidized HA powders have unique surface and microstructure characteristics. Scanning electron microscope (SEM) observation of the coating surface revealed well-formed splats that spread and flatten into disc configurations with no disintegration, reflecting adequate melting of the HA in the plasma and subsequent deposition consistency. The surface topography is generally flat with good overlapping of subsequent spreading droplets. Porosity in the form of macropores is substantially reduced. The cross-section microstructure reveals a dense coating comprised of randomly stacked lamellae. The tensile bond strengths of the SHA coatings, phase composition, and characteristics of the coatings generated with different particle sizes (125 to 75 μm, 45 to 75 μm, 20 to 45 μm, and 5 to 20 μm) showed that a high bond strength of ∼16 MPa can be obtained with SHA in the size range from 20 to 45 μm. This can be improved further by a postspray treatment by hot isostatic pressing (HIP). However, larger particle size ranges exhibited higher degrees of crystallinity and relatively higher HA content among the various calcium phosphate phases found in the coatings.     

Si粉粒径及其添加量对SiC陶瓷材料结构和性能的影响

将平均粒径为75 μm和48 μm、质量分数为0%~8%的Si粉分别添加到SiC陶瓷材料中,在1550℃下保温3 h烧成,研究Si粉粒径及其添加量对SiC陶瓷材料烧结性能、力学性能和显微结构的影响。结果表明:添加不同粒径及质量分数的Si粉可改善SiC陶瓷材料的显微结构,提高其烧结性能和力学性能;在一定范围内,较小粒径的Si粉更有利于形成均匀、致密的SiC烧结体,大幅提升SiC陶瓷材料的性能;当Si粉粒径为48 μm且添加的质量分数为4%时,SiC陶瓷材料的烧结性能和力学性能较优,其体积密度和显气孔率分别为2.58 g/cm3和13.5%,抗弯强度和洛氏硬度分别为25 MPa和115 HRB。      

超音速电弧喷射雾化制备的非互溶Ag-10Ni合金粉末的凝固特征

采用超音速电弧喷射气雾化制粉设备制备了难固溶Ag-10Ni合金粉末。研究了粉末粒度分布、形貌及凝固组特征，并对雾化熔滴的冷却速率及过冷度、凝固组织的凝固次序、形成机制进行了分析。结果表明：粉末分散性好、粒度主要集中在20pm～45μm、平均粒度32μm、形貌主要为球形和近球形；粉末颗粒凝固组织为富Ag基体＋弥散分布于基体中的细Ni相＋位于芯部的大直径初晶富Ni相，在大直径初晶富Ni相中弥散分布析出Ag相；富Ag基体的凝固组织为树枝晶组织，小颗粒粉末（〈20μm）枝晶间距小于0．2μm。     

Effect of Spraying Powders Size on the Microstructure,Bonding Strength,and Microhardness of MoSi2 Coating Prepared by Air Plasma Spraying

Molybdenum disilicide (MoSi₂) coatings were deposited on carbon steel by air plasma spraying technology with different feedstock powder sizes (i.e., powder A: ?15 + 2.5 μm, powder B: ?30 + 15 μm, powder C: ?54 + 30 μm, powder D: ?74 + 54 μm and powder E: ?106 + 74 μm). Phase composition and microstructure of coatings were characterized by x-ray diffraction (XRD) and scanning electron microscope. The bonding strength and microhardness of coatings were also evaluated. The XRD results show that there exists mutual transformation between T-MoSi₂ and H-MoSi₂ phase and part of Mo-rich phases are formed because of oxidization during the spraying process. With the increase of spraying powders size, the content of Mo-rich phases (Mo or Mo₅Si₃) and molybdenum oxide (MoO₃) in coatings decreases, and that of disilicide-rich phase (MoSi₂) in coatings increases. The oxidation degree of MoSi₂ particle gradually decreases during the spraying process with the increase of spraying powders size. The MoSi₂ is the main phase of the as-sprayed coatings when the spraying powders size is beyond 30 μm. With the increase of spraying powders size, the porosity of the as-sprayed coating increases, and the bonding strength of the coating gradually decreases. The hardness of coatings first increases and then decreases with the increase of spraying powders size.     

High pressure EIGA preparation and 3D printing capability of Ti—6Al—4V powder

Ti—6Al—4V alloy powder was processed by electrode induction melting gas atomization (EIGA) at high gas pressure (5.5–7.0 MPa). The effects of atomizing gas pressure on the powder characteristics and the microstructure, along with the mechanical properties of the as-fabricated block by laser melting deposition (LMD), were investigated. The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400 μm, and the median powder size (d₅₀) decreases with increasing gas pressure. The powders with a size fraction of 100–150 μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability. The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%–0.20%. Specimens fabricated by LMD are mainly composed of α+β grains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength (UTS) and yield strength of approximately 1100 and 1000 MPa, respectively. Furthermore, the atomized powders have a favorable 3D printing capability, and the mechanical properties of Ti—6Al—4V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.     

Preparation of Ti-Mo getters by injection molding

Ti-Mo getters have been fabricated via metal injection molding (MIM) using three kinds of Ti powders with different mean particle sizes of 46 μm,35 μm and 26 μm,respectively. The surface morphology,porosity,and hydrogen sorption properties of Ti-Mo getters formed by MIM using paraffin wax as a principal binder constituent were examined. It has been proven that the powder injection molding is a viable forming technique for porous Ti-Mo getters. The particle size of Ti powders and the powder loading influence...     

Powder Size Influence on Tensile Properties and Porosity for PM Ti_2AlNb Alloy Prepared by Hot Isostatic Pressing

Pre-alloyed powder of Ti_2AlNb alloy was prepared by electrode induction gas atomization method, and the powder was screened into fi ve kinds of powder size distribution. Fully dense Ti_2AlNb alloy was prepared by powder metallurgy(PM) using hot isostatic pressing. The properties of pre-alloyed powder and PM Ti_2AlNb alloy were tested. Results show that mean grain size of PM Ti_2AlNb alloy is infl uenced by powder particle size, but particle size has no signifi cant infl uence on tensile properties. Finer Ti_2AlNb powder has low Argon gas bubble ratio and high oxygen content, and poor fl owability of fi ner powder increases the degree of diffculty during degassing. As a result, big pores( 50 μm) are observed in PM Ti_2AlNb alloy prepared by fi ner powder and cause plasticity loss of tensile properties. In order to get a better comprehensive properties of PM Ti_2AlNb alloy, powder with an average size(～ 100 μm) is suggested.