粉末粒径和烧结温度对K418高温合金多孔材料显微结构及性能影响

以气雾化K418镍基高温合金球形粉末为原料，经过粉末松装烧结制备出高温合金多孔材料。通过对多孔材料微观结构、渗透性能、毛细性能及压缩强度进行表征，研究了原始粉末粒径和烧结温度对多孔吸液芯样品显微结构及性能的影响。结果表明，随烧结温度增加，样品的平均孔径和孔隙率减小；在相同烧结温度下，随着原始粉末粒径增加，样品的平均孔径和孔隙率增大。在烧结温度为1230℃，粉末粒径为53～150μm的条件下，多孔材料样品综合性能最优，渗透率为13.69×10-15 m2，毛细压力为22.1 kPa，压缩强度为86 MPa。     

Ni-Cr-Co-W-Mo-Al-Ti合金制备多孔材料的组织与性能研究

用粉末烧结法制备了孔结构为球形中空孔和线型中空孔的镍基多孔高温合金材料.对试样进行显微组织观察和力学性能测试.结果表明:制备的多孔高温合金材料的孔隙分布均匀,孔径大小一致.通过高温烧结,多孔合金骨架处的金属颗粒之间形成了烧结颈,发生了烧结结合.生成孔的孔隙度随造孔剂(尿素)的添加量增加而增加,当造孔剂的质量分数为40%时,可得到孔隙度为81.62%的球形多孔材料.多孔材料具有优良的能量吸收性能,其压缩性能随孔隙度和孔径的增加而下降.     

Ni—基渗层改性管冷凝强化换热实验研究

对Ｎｉ－基渗层管的强化冷凝换热进行实验,研究发现渗层管壁面具有低表面能,能够形成珠状凝结。与普通管相比,渗层管的整体换热效果好,总换热系数提高４０％以上,凝结换热系数提高约２倍,且随着管内流速的增大,渗层管强化换热的效果增强。     

稀土对机械合金化制备碳钢表面铬合金层的影响

以纯铬粉和Cr+RE[w(RE)=10%]硅铁粉末组合为原始粉末,利用行星球磨机,制备高铬合金层.采用X射线衍射、扫描电镜、能谱等方法分析合金层成分、显微结构及元素分布,并用多种实验手段检测合金层的显微硬度、抗热剥落能力及在NaCl和H2SO4腐蚀介质中的耐蚀性,以探讨稀土元素对合金层性能的影响.实验结果表明,合金层的显微硬度显著提高,抗剥落能力得到明显改善,在质量分数为3.5%的NaCl溶液中的耐腐蚀性能也得到较大提高.     

高通量换热管与烧结型高通量换热管性能介绍

高通量换热管是管壳式换热器强化传热技术深入研究下的产物。通过介绍汽化核心和汽泡形成阐释其强化传热原理。烧结型高通量换热管是多种高通量换热管型中具有代表性的一种,在有相变的沸腾工况下,其提高传热效果已被证实,但强化程度说法不一。通过蒸发池沸腾测试试验,比较公司自行研发的烧结型高通量换热管和普通光管的测试结果,探究高通量换热管的真实传热性能,对高通量换热器设计及高通量换热管的研发提供参考建议。     

人工髋关节用复合多孔钛股骨头制备方法的研究

本研究采用等离子旋转电极制取的Tc4钛合金球形粉末,涂覆在致密芯杆上,制成柄部表面多孔层厚度约2mm的复合多孔钛股头。本文着重研究了原始粉末粒度、烧结制度、基体表面粗糙度对复合多孔层的孔径、孔隙度以及多孔层与基体间结合强度的影响,同时还测定了复合多孔钛股头的机械性能。研究结果表明,材料的最大孔径主要取决于原始粉末粒度,并随粉末粒度的增大而线性增加。影响结合强度的主要因素是烧结制度、原始粉末粒度和基体表面粗糙度。其结合强度随烧结温度的提高、保温时间的延长、原始粉末粒度的下降和基体表面粗糙度的增加而增加。孔隙度仅取决于粉末的堆积状态。所获得的复合多孔钛股头的机械性能为σ_b=830~880 MPa,σ_0.2=810~840 MPa,σ=9.5~12.0%,ψ=26.0~33.0%。     

烧结气氛及时间对凝胶注模成形多孔NiTi合金性能的影响

多孔NiTi合金由于其优异的形状记忆性能和生物相容性而广泛应用于医用植入材料领域。以雾化Ni粉和机械破碎法制备的TiH_2粉末作为原料,以甲基丙烯酰胺作为单体,通过凝胶注模工艺制备出了性能良好的多孔NiTi合金,研究了不同烧结气氛和保温时间对多孔NiTi合金孔隙率、微观组织及力学性能的影响。结果表明:烧结气氛对烧结体的各项性能均具有较大的影响,同氩气及氢气气氛下烧结相比,真空烧结得到的合金孔隙分布均匀,相组成均一,孔隙率及机械性能较好,是理想的烧结气氛;随着烧结时间的增加,合金孔隙率降低,孔径分布更加均匀,抗压强度和杨氏模量增加,同时物相组成并未出现太大变化,单一的NiTi相很难通过延长保温时间来获得。对于固相体积分数分别为42%和45%的坯体,在真空环境下,烧结时间由1 h增加到4 h,其孔隙率分别由49.58%和48.52%降低到35.01%和33.49%,抗压强度由57.13和98.04 MPa增加到207.34和296.14 MPa,弹性模量由10.12和14.2 GPa增加到17.01和19.96 GPa。     

表面增强强化传热金属管装置性能的实验研究与分析

本文对制冷工质在表面增强型强化传热金属管外的凝结与沸腾进行试验,在采用不同表面增强型强化传热金属管、凝结型强化管的基础上,对其传热特性进行研究,实验结果显示冷凝管的换热性能与其管内水流速有十分密切的联系。本实验对传热金属管进行试验所采用的实验方法为对数平均温差法,对强化管的总传热系数进行确定,从而使得金属管的换热性能能够得到确定,为设计人员提供了有价值的参考。     

多孔CoTi生物材料的制备及性能

以NH_4HCO_3为造孔剂,采用粉末冶金烧结法制备低弹性模量、高孔隙度、孔隙尺寸适中和生物相容性良好的多孔CoTi合金。借助X射线衍射仪、金相显微镜、扫描电镜和力学实验机等对多孔CoTi合金的物相组成、孔隙特征和力学性能进行检测与分析。通过扫描电镜观测MG-63细胞的黏附情况及动物体内植入实验,采用Alamar blue法测定细胞增殖率。结果表明,多孔CoTi合金的孔隙特征受造孔剂特性和烧结温度的影响,细胞正常黏附并增殖。其中烧结温度为1 000℃,添加21%的NH_4HCO_3造孔剂,可制备出性能优异的多孔CoTi合金,该合金孔隙度为53.97%,平均孔隙尺寸为122μm,抗压强度44.8 MPa,弹性模量为2.16 GPa,这些孔隙特征和力学性能与人体松质骨相匹配,在培养6 h后MG-63细胞黏附形态完整,7d后增殖近一倍,植入动物体内12周后,材料与组织嵌合紧密,具有作为骨科替代材料的潜能。     

W—Ni—Fe合金多孔材料的研究

研究了由细钨粉加1～2％Ni—Fe(wt),通过压制、预烧结、研碎、分级和强化烧结制预合金粉,再由合金粗粉加2％(wt)硬脂酸或0. 4％(wt)聚乙烯醇,通过成形、预烧结和烧结成W-Ni-Fe合金多孔材料的工艺。探讨了团粒强化烧结温度、粉末粒度、成形压力、烧结温度和时间等工艺因素对多孔W-Ni-Fe合金性能的影响。研制出具有最大孔径130. 7μm,相对透气系数1. 78×10~(-2)L/min·cm~2·mm·H_2O,开孔孔隙度26. 46％,抗弯强度141. 3MPa的多孔W-Ni-Fe合金多孔材料,经抗热震使用实验,证明能用于净化1523K和11. 8MPa的高温高压燃气。     

激光烧结法制备原位增强型多孔镍基复合材料

对自熔性镍基合金和TiH_2的混合粉末进行了激光烧结实验,并采用XRD、SEM、EDX等分析手段对烧结试样的微观组织结构进行了表征,对试样中的孔结构及析出相的成形机制进行了初步探讨.结果表明,烧结后试样中存在原位增强相TiC、TiB_2和孔结构;大量微米级尺寸的圆孔以及呈放射状或针叶状的高温强化相CrB均匀分布于基体中.     

烧结温度对NiFe2O4/TiN复合陶瓷惰性阳极材料性能的影响

采用两步烧结法制备了掺杂质量分数为7%TiN的NiFe₂O₄/TiN复合陶瓷惰性阳极材料,重点研究了烧结温度对NiFe₂O₄/TiN复合陶瓷惰性阳极材料的微观结构及性能的影响.研究结果表明:随着烧结温度的升高,惰性阳极材料的晶粒间隙变小,气孔逐渐减少,晶粒间结合度提高,体积密度呈先升高后降低趋势,在1325℃时达到最大值5.20g/cm³,但材料内部存在微裂纹;烧结温度为1300℃时,材料表现出较好的综合性能,抗弯强度达到最大值66.77MPa,一次热震强度剩余率为95.54%,表现出良好的耐高温冰晶石熔盐腐蚀能力;烧结温度超过1300℃时,材料内部缺陷尺寸增加,电解质成分更容易渗入到阳极材料中,耐腐蚀性能下降.     

Powder Metallurgy Wear-Resistant Materials Based on Iron. Part 1. Materials Prepared by Sintering and Infiltration

Available information on the composition and methods of production of iron-based powder metallurgy wear-resistant materials is reviewed. It is shown that most developments in this field are based on the principle of obtaining wear-resistant material by the creation of a pseudoalloy with a clearly defined heterogeneous structure, in which the microhardnesses of the base material and a hard phase are substantially different. In addition to traditional methods, including pressing and sintering porous ingots and (in some cases) infiltration with a lower melting alloy, methods based on hot working sintered porous ingots under pressure have recently found wider application.     

Strain hardening behaviour of powder metallurgy alloys

Abstract

A model to describe the strain hardening behaviour of porous alloys, produced by powder metallurgy, is presented. It accounts for the influence of the matrix strain hardening ability, the initial porosity content and the pore geometry, and its predictive ability is verified with reference to sintered iron and an Fe–0·3%C sintered alloy. The necessity to introduce in the model a parameter able to account for the internal notch strengthening effect exerted by pores is emphasised. This parameter is found to be dependent on the sintering degree of the materials.     

THE MEASUREMENT AND FORM OF POROSITY IN THE LOOSE SINTERING OF COPPER COMPACTS

Abstract

Changes in surface area of specimens of loose-sintered –300-mesh spherical copper powder, measured by the BET gas-adsorption technique, are given for sintering temperatures of 700,800,900, and 1000°C under furnace atmospheres of hydrogen and argon, for times of 0–24 h. Porosity determinations, using a xylene-impregnation technique, show that the porosity is composed entirely of interconnected pores at 700, 800, and 900°C, connected porosity occurring only after 14 h sintering at 1000°C. Determinations of pore-size distribution are also given, measured by a technique based on a “capillary rise of a liquid in a porous material”. Results indicate that for specimens sintered under a hydrogen atmosphere, an overall increase in pore size occurs, whereas for specimens sintered at 800 and 900°C under an argon atmosphere the size of the majority of the pores remains constant, whilst a small percentage of extremely large pores is developed. Permeability coefficients calculated from surface-area and pore-size distribution data are compared with the experimental values.     

Effect of MnS powder additions and vibratory ball peening on corrosion resistance of sintered 316LSC stainless steels

Abstract

As sintered parts are to be machined after sintering, the MnS powder is usually added to improve the machinability. Vibratory ball peening is used for deburring and improving the surface finish of sintered components in local PM industries. The effect of the MnS powder content and vibratory ball peening on the corrosion resistance of the sintered 316LSC alloys was investigated. Experimental results show that the addition of MnS powder slightly decreases the sintered density. The weight loss rate of the sintered specimens immersed in the 10%FeCl₃ corrosion test solution increases slightly with increas- ing MnS content, but decreases with increasing sintering temperature. Vibratory ball peening effec- tively decreases the weight loss rate of the sintered stainless steels. The chromium atoms actively migrate across the phase boundary and diffuse into the MnS particles during sintering. This intensive chromium diffusion affects the corrosion performance of the sintered alloys with MnS added. The surface morphology of the as sintered and the ball peened specimens before and after the corrosion test were studied with a SEM.     

半导体用BaZrO3-xNa2CO3粉末合金的烧结性能和电导率分析

为了提高半导体用BaZrO₃粉末合金的综合性能,在BaZrO₃混合粉末内添加不同比例的钠盐(Na₂CO₃),并加热到1 360℃保温烧结3 h,通过实验对其烧结性能和电导率进行了表征。研究结果表明：在试样断面区域形成了孔洞,大部分晶粒的粒径介于0.5～0.7μm之间。随BaZrO₃添加量增大至10%时,粉末合金组织中形成了分散状态小孔,获得了较高的致密度。随着烧结温度增加,试样致密度与收缩率明显升高。添加Na₂CO₃后有利于完成BaZrO₃粉末合金烧结过程,通过液相烧结使粉末合金组织更加致密。加入合适含量的Na₂CO₃能够使BaZrO₃粉末合金达到更低烧结温度,获得更优烧结效果。当温度升高后,BaZrO₃-Na₂CO₃粉末合金都发生了电导率上升,加入Na₂CO<...     

Formation of properties and interparticular concrescence of hotformed powder materials. I. Influence of the method of obtaining powder materials on the concrescence of particles and on mechanical properties

Conclusions The quality of concrescence is a factor determining the properties of powder material. High-quality concrescence of particles is promoted by shear strains, both at the stage of SCP and of HF. The highest indicates K_1C are encountered in sintered and hotforged materials from reduced powder PZh2M3 with ramified shape of the particles.Segregation of impurity elements on the surface of open and closed pores of a porous compact upon sintering in vacuum leads to the stabilization of the interparticular boundaries. In the process of subsequent HF an anisotropic substructure therefore forms, the influence of interparticular segregation increases, and the indices Kic decrease. If the qualitY of concrescence in the sintered compacts is satisfactory, then the annealing of hot-forged specimens promotes the migration of the former interparticular boundary, its detachment from the impurity surface layer and inclusions of the second phase, and consequently it improves concrescence and crack resistance.Translated from Poroshkovaya Metallurgiya, No. 10(334), pp. 32–38, October, 1990.     

Liquid phase sintering of ferrous powder by carbon and phosphorus control

Abstract

Powder mixtures composed of liquid forming master alloy powder and coarse iron powder were sintered to near full density by having a high amount (20 wt-%) of liquid phase during sintering. This was made possible by the use of the Fe-P-C system with or without Cu. Without post-sintering treatment, a brittle microstructure was obtained. By means of altered C and P control and decarburisation heat treatment of the as sintered material, the final non-brittle microstructure was achieved. Using the open porosity and liquid phase as a diffusion path, rapid decarburisation is created and the local combination of carbon and phosphorus in the microstructure is avoided. In this way, iron phosphide is not formed on grain and/or particle boundaries. Presence of pores is confirmed to be beneficial for grain growth control.