316L不锈钢粉末温压与模壁润滑的高密度成形

通常在室温下，用内润滑厅式难以将316L不锈钢粉末压制成高密度生坯。本工作研究了316L不锈钢粉末的温压、模壁润滑和同时使用温压与模壁润滑的压制过程。研究发现：（1）模壁润滑和温压的同时使用可大幅度提高316L粉末的模压生坯密度。（2）复合润滑剂比单质EBS蜡更适用于有模壁润滑的温压过程，在工业常用的压制压力下，粒度〈74μm的316L粉末的生坯密度超过7．4g／cm^3。（3）316L粉末的高密度成形使得粉末颗粒强烈塑性变形，出现了晶粒内的亚晶结构。（4）同时使用模壁润滑和温压得到的高密度生坯在烧结过程不会发生体积膨胀，烧结密度超过7．56g／cm^3。     

420不锈钢粉末温压成形工艺

对420不锈钢粉末进行温压,探索温压工艺参数对压坯密度的影响,并对温压与室温模压（添加0．7％硬脂酸锌作润滑剂）后压坯的密度和弹性后效进行比较。实验结果表明：最佳粉末加热温度为90℃,最佳模具温度为120℃,最佳润滑剂含量为0．7％（质量分数）。在该工艺条件下,当压制压力为784MPa时,压坯密度达到6．86g／cm^3：经1130℃烧结后样品密度略有下降,为6．83g／cm^3,硬度为HRC33。温压压坯密度比室温模压的提高约0．2g／cm^3,温压后压坯弹性后效较室温模压小。     

压坯密度对烧结NdFeB磁体磁性能的影响

采用速凝片（SC）、氢破（HD）和气流磨（JM）工艺制备钕铁硼磁粉,研究了压坯密度、烧结温度对磁体取向度、微观结构和磁性能的影响。结果表明：选择合理的压坯密度（ρx=3．4g／cm3）可以使磁体在模压和液相烧结过程中保持较高的取向度,剩磁提高约2％。在低温度（1055℃）烧结时,可以获得较为理想的显微组织,主相晶粒细小...     

冷压烧结法制备Al2O3/Cu复合材料

采用压坯烧结加复压复烧工艺制备出A12O3／Cu复合材料。Al2O3颗粒的尺寸分别为2μm、7μm、10μm，体积含量分别为5％、10％、15％。结果表明，一次烧结工艺是影响材料密度的关键因素；复压及复烧能够进一步提高复合材料的密度及性能。金相组织观察表明，Al2O3颗粒分布均匀，与基体的界面结合良好。     

含Fe-Mo-B预合金粉铁基合金的温压成形与液相烧结

研究了含Fe-Mo-B预合金粉的铁基合金的温压和液相烧结行为,分析了成形温度和压制压力对压坯密度的影响,对比了不同Fe-Mo-B预合金粉含量下烧结前后试样的密度和显微组织．结果表明:与常温成形相比,温压能够明显提高压坯密度,在120℃时含10%和15．4% Fe-Mo-B预合金粉的压坯密度分别提高0．34g·cm^-3和0．32g·cm^-3;混合粉中加入一定量的Fe-Mo-B预合金粉,压坯烧结时可形成液相烧结,促进材料的致密化,密度最大可达7．49g·cm^-3,其相对密度为97．74%,并可获得典型的贝氏体组织．     

温压粉末冶金材料的性能与公差

为提高粉末冶金对其他制造技术的竞争性，需要适宜的合金系以及在降低加工费用的情况下提高力学性能并保持公差控制精度的工艺技术。在加热了的模具中压制加热的粉末是一种经一道工序就使密度提高到7.2～7.5g／cm3的新工艺。通过该工艺，可以得到相当于复压／复烧的密度水准与力学性能。然而，通过温压提高性能须兼而保持与传统粉冶工艺路线相同等级的公差猜度。本文介绍了这种特性粉末以及一些低合金粉冶材料（在温压与烧结后）的力学性能。同时也叙述了用温压工艺生产部件时有关公差精度的一些试验结果。     

铁基粉末温模压制技术的研究

温压工艺是一种能以较低成本制备高密度铁基粉末冶金零部件的新技术，但该技术在工业化应用中，需要昂贵的设备投入及改造费用，限制了其大规模应用。论文作者利用具有优异室温润滑性能的润滑剂，以经过退火和未退火处理的雾化铁粉配制的、材质为Fe-2Ni-1.5Cu-0．5C的2种混合粉末为原料，研究制备高密度粉末冶金材料的常规压制和温模压制工艺。结果显示，粉末中较理想的润滑剂含量范围为0．1％～0．3％（质量分数），此时，润滑剂含量对压制效果影响不明显。在压制压力为763MPa、模具温度为100℃的条件下，含0．1％润滑剂的2种粉末压坯密度分别达到7．50g／cm^3和7．43g／cm^3，对应的脱模压力为34MPa和42MPa，与传统温压效果相接近，而采用传统的室温压制也可以获得7．36g／cm^3的压坯密度。     

低温温压工艺

较系统地研究了低温温压工艺,考察了粉末温度、模具温度、润滑剂含量和压制压力对温压 密度的影响。实验结果表明:低温温压中最佳的模具温度、粉末温度分别为120℃和100℃;粉末 中最佳的润滑剂含量为0.65％;当压力为686 MPa时,Fe-1.5Cu-0.5C和Fe-1.5Ni-0.5Mo-0.5Cu- 0.5C(均为质量分数,％)材质体系的粉末压坯密度分别达到了7.42和7.41 g／cm3;2种粉末的温 压坯件经烧结后都发生了收缩,进一步提高了密度,合金Ni,Mo元素等具有优良的烧结强化效 果;采用低温温压工艺可以生产出烧结密度为7.34 g／cm3,烧结硬度为HRC 28,热处理后表观硬 度为HRC 54的高性能P／M齿轮。     

温压法处理转炉污泥铁粉

对转炉污泥铁粉进行了系统的温压试验。研究了温度、压制压力、石墨量、润滑剂量对污泥铁粉温压制品性能的影响。结果表明,用正匀试验方法优选出的温压工艺可使零件生坯密度达7．20g/cm^3,烧结件密度达7．12g/cm^3,压溃强度达406．1MPa。     

不锈钢金属蜂窝的制备、组织结构及力学性能研究

采用410L不锈钢粉末与增塑剂的混合物，用增塑挤压烧结法制备了不锈钢金属蜂窝，研究了挤压成形过程、烧结温度和时间对蜂窝组织结构的影响及蜂窝的压缩性能。结果表明，合适的挤压料配比为70％～80％，挤压力为9．5～11MPa；随烧结温度、时间的提高，蜂窝的表观密度等结构参数都提高，但温度的影响大于时间的影响；烧结组织由Fe—Cr固溶体、（Fe，Cr），Si和（Fe，Cr）3C组成，最佳烧结参数为1235℃及25min；蜂窝屈服强度与表观密度密切相关；径向压缩为单一层状屈服，最大屈服强度可达40．9MPa（表观密度2．16g／cm^3）；轴向压缩变形为多变形带屈服，最大屈服强度为224．7MPa（表观密度2．02g／cm^3）。     

THE INFLUENCE OF A PARTIALLY WETTING SECOND PHASE ON THE SINTERING OF SOLID PARTICLES

Abstract

A geometrical model is considered which describes the sintering kinetics between two solid, spherical particles covered by a partially wetting second phase. Conditions selected are such that the grain boundary is not penetrated by the second phase. The model is kinetically similar to the case of solid-state sintering by grain-boundary diffusion and can also be compared with Kingery’s model of liquid-phase sintering. It predicts that the sintering rate of two solid particles remains virtually unchanged when a second phase (solid or liquid) is added. An example is the sintering behaviour of SmCo₅. The applicability of the model to carbide-metal and oxide-metal systems is discussed.     

粉末烧结法制备多孔Ti-6Al-7Nb合金的工艺优化

以Ti粉、Al粉和Nb粉为原料,采用粉末烧结法制备多孔Ti-6Al-7Nb合金,利用正交试验考察了混料时间、压制压力、烧结温度、烧结时间对孔隙率的影响。结果表明,各因素对孔隙率的影响主次顺序为:烧结温度烧结时间压制压力混料时间。结合骨科植入所需材料的孔隙率和孔径分布情况确定最优工艺参数为:混料时间4 h,压制压力100 MPa,烧结温度1 100℃,烧结时间2.5 h,采用最优工艺制备的多孔Ti-6Al-7Nb孔隙率为32%,孔径尺寸集中分布于5~12μm范围。     

耐磨粒子和活化烧结剂对铜合金动密封材料的力学和摩擦磨损性能的影响

本文用热压工艺制造了一种铜合金基动密封材料。研究了耐磨粒子和活化烧结剂的含量对其机械性能和摩擦磨损性能的影响 ,并且观察了其显微组织。试验结果表明 ,随着耐磨粒子和活化烧结剂的增加 ,机械性能随之提高 ;活化烧结剂改善了烧结性能 ,降低了材料的孔隙度 ;耐磨粒子的加入使耐磨性能增加一倍     

微波烧结过程中Cu_(60)Cr_(40)合金组织演变的研究

采用机械合金化和冷压微波烧结法制备了Cu_(60)Cr_(40)合金,通过X射线分析和SEM扫描电镜分析Cu_(60)Cr_(40)合金的相组成和显微组织,研究了微波烧结过程中Cu_(60)Cr_(40)合金组织的演变规律。结果表明:Cu_(60)Cr_(40)合金粉体和冷压压坯组织呈层片状;随烧结温度的提高,Cu_(60)Cr_(40)合金压坯在烧结过程中由层片状组织向短棒状或球棒状转变,晶界逐渐明显,孔隙减少,致密度增加,由固相烧结转变为液相烧结。     

Explosive pressing of a TiC-TiNi powder composite

Conclusions Explosive pressing enables specimens of relative densities up to 95% to be obtained, whereas the maximum attainable density after static pressing does not exceed 70%. There exist optimum sintering temperatures and compact densities, which are different for the static and explosive pressing methods. It is important that the optimum temperature of sintering after explosive pressing is 150°C lower than that of sintering after static pressing. This enables the sintering of the hard metal to take place virtually in the absence of a liquid phase. Explosive pressing is performed without a plasticizer, which simplifies the preparation of the powder mixture, enables the rate of heating in sintering to be increased, and improves the conditions of operation of the sintering furnace. Compared with static pressing, the explosive method ensures an about 50% lower residual porosity, a more fine-grained structure, and higher transverse rupture strength.Translated from Poroshkovaya Metallurgiya, No. 7(271), pp. 27–31, July, 1985.     

高密度铁基粉末冶金零部件制造原料的研究

温压粉末原料是采用温压成形技术制造高密度粉末冶金零件的基础和温压工艺的技术核心。高价格的进口温压粉末制约了我国高密度铁基粉末冶金零件的开发与应用,因此,必须开发出符合我国国情的温压粉末原料体系。作者根据我国资源特点,采用鞍钢产水雾化铁粉、水雾化低合金钢粉和攀枝花钢铁公司产转炉烟尘铁粉为原料,进行了制备相应体系的温压粉末原料和温压工艺参数优化的研究。以水雾化铁粉为原料设计制造的Fe-1.5Ni-0.5Mo-0.5Cu-0.6C粉末经637MPa压制,温压密度为7.46g/cm~3;压坯的回弹率为0.03％.在1150℃烧结40 min后,收缩率为0.025％。而以转炉烟尘铁粉设计制造的Fe-1.5Ni-0.5Mo-0.5Cu-0.6C粉末经686 MPa压制,压坯密度达7.35g/cm~3;以Fe-1.5Ni-0.5Mo水雾化合金钢粉为原料制造的Fe-1.5Ni-0.5Mo-1.5Cu-0.8C粉末在686 MPa时压制密度为7.35g/cm~3。这些粉末原料的设计为我国高强度铁基粉末冶金零部件的制造创造了条件。     

Some Features of Coalescence Processes and Mechanisms in Systems of Nonmetallic Crystalline Particles

The influence of particle size, presence of soluble impurities, and the development of solid-state polytype transitions in systems of nonmetallic crystalline particles on coalescence mechanisms during sintering is considered. The following cases that have not been studied previously are discussed. Coalescence is activated by oxygen during sintering fine plasma chemical powders of AlN, TiC, and TiN. Its mechanism may be considered as alloy formation realized by movement of a boundary between areas differing in oxygen concentration. Development of this coalescence governs the formation of collective grain growth centers. Polytype transitions in self-bonded SiC give rise to the occurrence of Ostwald coalescence accomplished as recrystallization by the grain in grain type. Polytype transitions in SiC and AlN may cause the growth of fine monopolytype grains at the expense of coarse grains consisting of a collection of multilayer polytypes. On the example of silicon-bonded SiC it is shown that during liquid-phase sintering of ceramic materials with solubility of solid phase in the liquid phase three types of Ostwald coalescence may be realized differing in the mass-transfer mechanisms: reprecipitation through the liquid phase (solution of carbon in silicon); joining of two or more single original SiC particles by a single-crystal shell forming as a result of crystallization of the condensed phase from the melt-solution; combined reprecipitation through a liquid phase and recrystallization by migration of boundaries between particles.     

Co-Cr-Mo-Si颗粒强化铁基材料的研制

采用烧结 -熔渗和后续热处理工艺制备了Co Cr Mo Si硬质相颗粒强化的高性能铁基粉末冶金气门座材料。研究了不同状态下材料的显微组织以及Co Cr Mo Si硬质相颗粒和合金元素对材料性能和组织变化的影响。结果表明 ,材料烧结态孔隙多 ,硬质相颗粒与基体结合不完全。熔渗后 ,孔隙明显减少 ,致密度较高 ,显微组织为针状珠光体、铁素体、粒状碳化物和游离铜 ,硬质相颗粒作为独立相存在于组织中 ,并且与基体形成较为理想的界面结合强度。热处理后 ,显微组织为细针状的马氏体、残余奥氏体、游离铜 ,细小粒状的碳化物和以独立相存在的硬质相颗粒。这种组织可以明显提高材料的硬度、密度和强度 ,并且还具有一定的塑性和冲击韧性。合金元素的加入 ,可以细化晶粒 ,提高材料的机械性能     

Effect of porosity on the volume changes experienced by Al-Cu compacts during liquid-phase sintering

Conclusions In the Al-Cu system a linear relationship between the end and starting porosities exists only at porosities exceeding 20%. At a smaller pore content the linearity is disturbed by the presence of an irreducible oxide phase on the aluminum particles. Decreasing the starting compact porosity results in greater growth in the first stage of sintering and smaller shrinkage in the second. The extent of the compact growth preceding the shrinkage may markedly exceed that due to copper and aluminum atom diffusion under conditions of uniform reaction of the liquid phase on all the surfaces of the particles. The anomalously large compact growth in the first stage of sintering is due to a negative regrouping of particles resulting from an uneven Kirkendall flow of material inside the particles, bringing about a change in their shape. The extent of shrinkage is not apparently linked with the structure forming during sintering, but depends on the starting porosity. Pores in a compact affect grain growth during sintering by inhibiting it.Translated from Poroshkovaya Metallurgiya, No. 7(295), pp. 22–26, July, 1987.     

制备工艺对碳化硼陶瓷性能的影响

以活性炭和碳化硅为烧结助剂,采用真空热压工艺,制备了碳化硼陶瓷材料.研究了真空热压工艺、烧结助剂对碳化硼陶瓷性能及断口的影响,结果表明,以活性炭和碳化硅为烧结助剂的碳化硼陶瓷随热压压力增加,开口孔隙度减小,相对密度和抗弯强度增加.添加活性炭的碳化硼陶瓷在热压压力为35MPa下,开口孔隙度有最小值(1.7%),相对密度(91.7%)和抗弯强度(277.6MPa)达最大值;以碳化硅为烧结助剂的碳化硼陶瓷在热压压力为30MPa下,开口孔隙度有最小值(0.66%),相对密度(91.9%)和抗弯强度(173.6MPa)达最大值.添加活性炭的碳化硼陶瓷随保温时间由30min增加到90min,开口孔隙度逐渐减小而相对密度逐渐增加(90min时分别达到0.19%、99.6%),抗弯强度先增加后减小,在保温时间为60min时抗弯强度达到最大值(351.7MPa).在相同的真空热压工艺下,添加活性炭的碳化硼陶瓷与添加碳化硅的碳化硼陶瓷相比,其开口孔隙度低,抗弯强度高.初步探讨了真空热压工艺以及添加剂促进碳化硼陶瓷烧结的机理.