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。     

低压等离子喷涂制备喷雾干燥型与机械混合型ZrB2-MoSi2复合涂层的比较研究

利用喷雾干燥与真空烧结技术制备团聚型ZrB2-MoSi2复合粉末,以这些粉末为原料,通过低压等离子喷涂法制备了ZrB2-30 wt.%MoSi2复合涂层(SZM涂层)。作为对比,利用机械混合粉末制备了ZrB2-30 wt.%MoSi2复合涂层(MZM涂层)。借助SEM、XRD和EDS等对涂层的组织结构进行研究,并利用霍尔流速计和松装密度计对团聚粉末的流动性和松装密度进行了测试。此外,对涂层的显微硬度、孔隙率和氧化特性均进行了研究。结果表明：喷雾干燥粉末在1200℃真空烧结1h后,它的流动性和松装密度分别达到25.8 s/50g 和1.12 g/cm3。与MZM涂层相比,SZM涂层中的MoSi2分布更加均匀,而且结构更加致密。所以团聚粉末制备的涂层在1500℃的抗氧化性能更好。     

Al2O3弥散强化铜-锡含油轴承的制备和性能

以内氧化法制备的Al2O3弥散强化铜(简称“弥散铜”)粉和雾化锡粉为原料,采用扩散合金化法制备弥散铜-锡合金粉末,经压制、烧结制备弥散铜-锡含油轴承,研究扩散温度对弥散铜-锡粉末合金化程度的影响,并考察烧结温度对含油轴承性能的影响。结果表明:弥散铜-锡混合粉末经700℃扩散处理后,锡在弥散铜基体中分布均匀,制备的弥散铜-锡合金粉末的松装密度为2.40 g/cm3、流动性为39.6 s(50 g);轴承压坯在800℃及以下温度烧结时,粉末颗粒之间没有发生显著烧结,导致轴承性能较差。当烧结温度为850℃时,粉末颗粒之间形成一定的冶金结合,轴承强度显著提升,开孔率小幅降低。在900℃及以上温度烧结时,轴承发生显著收缩,开孔率明显降低。850℃烧结制备的弥散铜-锡含油轴承的径向、轴向尺寸变化率均约为1.0%,压溃强度为160 MPa,显微硬度为166 HV0.05,开孔率为26.0%。     

低压等离子喷涂制备喷雾干燥型与机械混合型ZrB_2-MoSi_2复合涂层的比较研究（英文）

利用喷雾干燥与真空烧结技术制备团聚型ZrB_2-MoSi_2复合粉末,以这些粉末为原料,通过低压等离子喷涂法制备了ZrB_2-30%MoSi_2(质量分数)复合涂层(SZM涂层)。作为对比,利用机械混合粉末制备了ZrB_2-30%MoSi_2复合涂层(MZM涂层)。借助SEM、XRD和EDS等对涂层的组织结构进行研究,并利用霍尔流速计和松装密度计对团聚粉末的流动性和松装密度进行了测试。此外,对涂层的显微硬度、孔隙率和氧化特性均进行了研究。结果表明:喷雾干燥粉末在1200℃真空烧结1 h后,它的流动性和松装密度分别达到25.8s/50 g和1.12 g/cm~3。与MZM涂层相比,SZM涂层中的MoSi_2分布更加均匀,而且结构更加致密。所以团聚粉末制备的涂层在1500℃表现出更好的抗氧化性能。     

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。     

冷压烧结制备高密度粉末冶金零部件的新方法

冷压外加烧结法是获得高密度粉末冶金零部件的一种低成本工艺，工艺研究集中于制备密度尽可能高的粉末冶金部件。为了减小压制过程中模壁与粉体间的摩擦，提高未烧结件的密度和均匀性，传统粉末压制与烧结工艺中元素粉末混合时须添加润滑剂，然而大量残留的润滑剂会限制压制件的致密化．降低湿态强度。因此，烧结初始阶段须去除残留的润滑剂。润滑剂于150℃溶化，600℃左右开始分解。润滑剂的分解会使烧结密度减小。另一方面压坯孔洞内的气体也会降低制件的密度，润滑剂对压制工艺的影响已进行了许多研究，但孔洞内气体对压制工艺的影响尚未见有关报道。     

钼包铁粉对Fe-2Cu-1Mo-0.8C合金显微组织、工艺性能和力学性能影响

分别采用元素混合粉和钼包铁粉将钼元素引入到Fe-2Cu-1Mo-0.8C成形混合料中,经压制烧结后得到烧结体,考察了两种钼元素引入方式对粉末工艺性能及烧结体显微组织和力学性能的影响.结果表明,由钼包铁粉所制备的Fe-2Cu-1Mo-0.8C成形混合料松装密度和流动性都优于元素混合粉末,分别提高了0.22 g/cm3和2.14 s/50 g.经800 MPa压力压制后,由钼包铁粉制备的压坯密度为7.29 g/cm3,于1150℃烧结90 min后得到烧结体的密度为7.26 g/cm3.烧结体的显微组织以珠光体和铁素体为主,由钼包铁粉制备的烧结体组织更为致密,钼元素在烧结体中分布更均匀,其抗拉强度和硬度分别为533 MPa和98.2 HRB,由元素混合粉制备的烧结体的抗拉强度和硬度分别为501 MPa和93.5 HRB.     

等离子球化制备球形CaF2/BaF2共晶粉末*

探究了使用大气等离子喷涂设备制备适合热喷涂使用的球形CaF2/BaF2共晶粉末的可能性。68%BaF2、32%CaF2粉末(质量分数)经过1 100℃真空烧结后,形成致密的块状氟化物共晶。机械破碎后的氟化物共晶经过等离子焰流重熔后得到了球形的氟化物共晶。使用F14-1流动性和松装密度测定仪测量球化前后粉末的流动性和松装密度。采用扫描电子显微镜,XRD表征球化前后粉末的形貌和物相组成。结果表明:球化后的粉末呈现较好的球形,球化后粉末的流动性和松装密度较球化前也有较大的改善:球化后共晶粉末的流动时间为55.20s/50g,松装密度为1.89g/cm3;另外,球化后共晶粉末还表现出良好的高温润滑性能:含有10%CaF2/BaF2共晶(质量分数)的镍基涂层在600℃和800℃的平均摩擦因数都小于0.3。     

不同粒径Ti粉的高速压制行为和烧结性能

以平均粒径为150,75,48和38μm的4种Ti粉为原料(依次定义为A,B,C和D粉末),采用高速压制技术进行成形,考察粉末粒径对压坯密度、最大压制力和脱模力的影响,进一步研究粉末的高速压制特性和压坯的烧结性能.结果表明,高速压制的压坯密度与粉末粒径和松装密度有关.冲击能量较小时,压坯密度主要取决于松装密度,而冲击能量较高时,则主要取决于粉末粒径.在冲击能量≤761 J下成形时,具有最大松装密度的B粉末所获得的压坯密度最高;进一步增大冲击能量,平均粒径最大的A粉末所获得的压坯密度最高.粉末粒径对压坯密度和最大压制力具有相似的影响,并且4种粉末的最大压制力和压坯密度之间的关系均符合黄培云压制方程;但粉末粒径对脱模力无明显影响.试样的烧结密度随粒径的细化而增加,同时伴随着不同程度的晶粒长大.4种压坯经1250℃真空烧结后,最终均获得了近全致密的试样.     

粉末制粒工艺对金刚石刀头冷压坯质量的影响

采用容积式自动装料冷压成型法生产金刚石锯片刀头,需要对流动性不好的混合粉料进行制粒处理,使粉料既有适当的流动性又具有稳定的松装比,从而实现刀头冷压坯重量和厚度偏差的稳定性。采用擦筛法和高速搅拌法两种工艺进行粉末制粒,对制粒后粉末颗粒的形貌、松装密度、流动性以及最终冷压坯的质量进行实验研究。结果表明:擦筛法制粒的粉末松装密度小于高速搅拌法制粒的粉末;高速搅拌法制粒粉末的流动性大于擦筛法;采用高速搅拌法制粒得到的冷压坯的重量均一性比擦筛法制粒的更好。     

Die wall lubricated warm compaction of iron-based powder metallurgy material

Lubricant is harmful to the mechanical properties of the sintered materials,Die wall lubrication was applied on warm compaction powder metallurgy in the hope of reducing the concentration level of the admixed lubricant.Iron-based samples were prepared by die wall lubricated warm compaction at 175℃,using a compacting pressure of 550MPa.Emulsified polytetrafluoroethylene(PTFE) was used as die wall lubricant.Admixed lubricant concentration ranging from 0 to 0.5% was tested.Extremely low admixed lubricant contents were used.Results show that in addition to the decrease in ejection forces,the green density of the compacts increases with the decrease of admixed lubricant content until it reaches the maximum at 0.06% of lubrcant content,then decreases with the decrease of admixed lubricant content.The mechanical properties of the sintered compacts that contain more than 0.06% admixed lubricant are better than those of the samples that contain lesser lubricant.No scoring was observed in all die wall lubricated experiments.     

Warm compaction powder metallurgy of Cu

A series of experiments were carried out using different admixed lubricant contents, different compaction pressures and temperatures in order to study the warm compaction of copper powder. Results show that too much admixed lubricant will lead to the squeeze out of the lubricant from the compact during the warm compaction processing of Cu powder. Results also show that blisters can be found in sintered samples that contain lubricant less than 0.15%(mass fraction). Optimal warm compaction parameters for producing high density powder metallurgy copper material are obtained. Compacts with green density of 8.6 g/cm^3 and a sintered density of 8.83 g/cm3 can be produced by warm compacting the Cu powder, which contains 0.2% admixed lubricant, and is compacted at 145℃ with a pressure of 700 MPa.     

Analysis of density and mechanical properties of high velocity compacted iron powder

A new method for producing higher density PM parts, high velocity compaction (HVC), was presented in the paper. Using water atomized pure iron powder without lubricant admixed as the staring material, ring samples were compacted by the technique. Scanning electron microscopy (SEM) and a computer controlled universal testing machine were used to investigate the morphologies and the mechanical properties of samples, respectively. The relationships among the impact velocity, the green density, the sintered density, the bending strength and the tensile strength were discussed. The results show that with increasing impact velocity, the green density and the bending strength increase gradually, so the sintered density does. In addition, the tensile strength of sintered material is improved continuously with the sintered density enhancing. In the study, the sintered density of 7.545~g/cm³ and the tensile strength of 190~MPa are achieved at the optimal impact velocity of 9.8 m/s.     

The influence of powder apparent density on the density in direct laser-sintered metallic parts

In direct laser sintering, the density is expected as high as possible for the industrial application. Since the density not only determines the industrial acceptance, but also limits the accuracy of the parts. This paper reports on the influence of the powder apparent density on final density of the sintered part's in direct laser sintering of Cu-based metal powder. The relative densities of the sintered parts with the different apparent densities using different process parameters have been investigated. The result shows that the apparent density has the most significant effect on final density of the sintered part. The final density increases with the increase of the apparent density. It is easy to get a higher final density in direct laser sintering process if a higher apparent density is used. However, the final density seems to have an upper limit for a given metal powder system.     

增材制造用高流动性铝合金粉末制备技术研究

采用自主开发的旋转盘离心雾化实验装置进行雾化制备增材制造用铝合金粉末实验研究,通过开展雾化盘实验研究优选出粒度分布较均匀收得率较好的盘形,并获得其结构和工艺参数的影响规律;通过对制得的铝合金粉末性能和3D打印成型件物理性能进行检测。结果表明:离心雾化制备的铝合金粉末具有高流动性、窄粒度、高球形度、高松比,表面光洁无卫星粉,无空心粉等特点,同时3D打印离心雾化样件熔覆道均匀,孔洞缺陷少,致密度和力学性能明显优于气雾化样件,尤其是抗拉强度和屈服强达到495和320 MPa,相比气雾化粉打印样件提高近10%。     

Application of compression lubricant as final porosity controller in the sintering of tungsten powders

Sintering behavior of two tungsten powders (1.2 μm and 6 μm) was studied for preparing infiltrable porous skeleton. Both powders were compressed by mechanical press (MP) and cold isostatic press (CIP) with and without stearic acid respectively as compaction lubricant. Results showed that presence of solid lubricant powder in addition of its essential effect on soundness of parts, depending on its size and distribution, could mainly affect sintered microstructure. Stearic acid as compaction lubricant in addition of decreasing friction between particles during the compaction, has acted as spacing particles between primary powder particles. In the cases that lubricant particles are much bigger than tungsten particles a big pore remained after evaporation of lubricant. During the sintering, big pores became bigger due to coarsening mechanism and formed an interconnected network of pores and on the other hand small pores shrank or even disappeared due to densification. By exact controlling of the size of tungsten powder and lubricant powder, infiltrable tungsten skeletons with 80% of theoretical density were produced successfully at low sintering temperatures such as 1500 °C.     

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。     

Warm compacted NbC particulate reinforced iron-base composite(Ⅰ)--Effect of fabrication parameters

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镁对氢化钛烧结致密化的影响

以氢化钛粉末和镁粉为原料,利用模压工艺制备纯钛,主要研究了镁对氢化钛粉末烧结致密化的影响。结果表明,少量镁的添加能够促进氢化钛粉末的烧结致密化,而过量镁则降低烧结密度,镁添加量为0.5%(质量分数,下同)时效果最优,将烧结体相对密度由96.5%提高到98.7%。通过对烧结过程动力学、镁还原氧化钛反应的热力学和动力学,以及烧结体成分进行分析,发现少量镁促进氢化钛烧结致密化的机理为:真空烧结时镁从坯体中挥发,形成的镁蒸气对粉末颗粒表面的氧起到净化作用,提高了烧结活性,从而提高烧结密度。