硬质颗粒增强型新能源汽车铁基粉末冶金阀座的热处理工艺

以W6Mo5Cr4V2高速钢粉末为基体粉末,添加Fe-Mo、Co-Cr-Mo等硬质颗粒,压制成阀座坯体,然后以专用渗铜粉(Cu-Fe-Mn)作为熔渗剂,通过真空高温熔渗制备颗粒增强铁基粉末冶金阀座,进行淬火和回火热处理,研究淬火温度与回火温度对阀座材料基体与硬质颗粒显微硬度以及阀座材料摩擦磨损性能的影响,并通过正交试验优化材料的热处理工艺。结果表明:淬火温度对阀座材料的W6Mo5Cr4V2基体和Fe-Mo、Co-Cr-Mo硬质颗粒硬度和耐磨性能影响较大,在1 140~1 260℃温度下淬火时,Fe-Mo和Co-Cr-Mo硬质颗粒发生明显扩散。淬火对铜覆盖区域的碳化物影响较小,覆盖区域内未溶碳化物较多且尺寸较大。淬火温度为1 220℃时,材料基体以及Fe-Mo和Co-Cr-Mo硬质颗粒的显微硬度(HV)分别为528,892和632。回火温度对阀座的硬度影响小,回火温度为520℃时阀座硬度最高。在淬火温度为1 220℃,回火温度5 20℃,回火次数为3次的条件下,阀座的硬度(HRC)达到49.2,磨损量为0.029 5 g。     

骨架密度对C/C-ZrC骨架压力浸渗铜的影响

采用CVI法增密针刺毡炭纤维预制体制备C/C坯体,然后用PIP法在C/C坯体中加入ZrC陶瓷制得不同密度的C/C-ZrC骨架,再对C/C-ZrC骨架进行压力浸渗铜,研究了不同密度的C/C-ZrC骨架压力浸渗铜的组织和性能.结果表明:密度分别为1.29、1.35、1.49、1.56 g/cm3的C/C-ZrC骨架经压力浸铜后密度分别达到2.05、2.28、2.39、2.49 g/cm3,铜都不同程度地浸入到骨架中的网胎层和炭纤维束间的孔隙中,表明ZrC的加入改善了Cu对骨架中C/C的浸润性,且浸润性改善效果随骨架中ZrC量的增加、骨架密度的提高而增强.C/C-ZrC骨架密度显著影响着C/C-ZrC骨架压力浸渗铜的抗弯强度、抗压强度,随着C/C-ZrC骨架密度的升高,C/C-ZrC骨架压力浸渗铜的抗弯强度、抗压强度随之增加.     

冷处理及回火次数对刀剪用M390粉末钢组织和性能的影响

通过对M390粉末不锈钢进行淬火、冷处理和低温回火，研究了热处理对合金显微组织和力学性能的影响。结果表明：冷处理降低合金中残余奥氏体的数量，大幅度提高材料硬度和抗弯强度；1 180℃淬火试样冷处理后，随回火次数的增加，单位面积碳化物颗粒总数和平均粒径增加，硬度下降，一次回火后硬度达到61.1 HRC;1 130℃淬火试样冷处理后，随着回火次数增加，单位面积颗粒总数不断增加，平均粒径和硬度下降，一次回火后硬度达到60.0 HRC；淬火温度和回火次数对抗弯强度影响不大，合金抗弯强度为4 000 MPa左右。     

(Ti,V)C35CrMo原位烧结钢结硬质合金的热处理及性能的研究

研究了(Ti,V)C35CrMo钢结硬质合金热处理组织与力学性能的关系。结果表明,1000℃淬火500℃回火发生二次硬化现象,硬度达86HRA左右,抗弯强度为1540MPa。断口形貌特征为硬质相解理、基体准解理及韧窝。基体形变磨损和硬质相脱落是钢结硬质合金的磨料磨损机理。1000℃淬火和250℃、500℃回火后合金的耐磨性分别是高铬铸铁的3.8倍和3.5倍。     

C/C-ZrC骨架压力浸渗Cu的微观结构与力学性能

以炭纤维针刺整体毡为预制体,先采用CVI增密工艺制备密度1.10 g/cm3的C/C坯料,然后通过PIP法将ZrC陶瓷加入C/C制得密度1.50 g/cm3的C/C-ZrC骨架,最后对C/C-ZrC骨架压力浸渗Cu.结果表明:C/C-ZrC骨架的浸铜体积分数达24％,开孔浸铜率达74％,浸铜后的材料密度3.63 g/cm3,开孔率5.6％,获得良好的浸铜效果.浸入骨架的Cu填充到骨架中网胎层和纤维束间的孔隙里,与ZrC、炭一起构成骨架浸铜材料的基体.骨架中的炭纤维对基体增韧增强,使C/C-ZrC骨架浸铜后的材料抗弯强度达到302 MPa,抗压强度达到342 MPa.     

热处理状态对H13模具钢渗氮层的影响

 采用X射线衍射、扫描电镜及显微硬度等技术,综合比较和分析了H13模具钢在不同热处理状态下经相同气体渗氮处理后表层的组织结构和硬度。结果表明,经淬火＋二次回火和淬火+三次回火的试样渗氮后,渗氮层厚度均达到约0.24 mm,致密化合物层厚度达到10 μm以上,表面硬度HV达到950 (约为HRC 67)。这两种热处理状态下渗层中化合物层均由ε相（Fe2N）、γ′相和Fe3O4构成,扩散层均由α Fe相、ε相（Fe3N）、CrN相和γ′相构成,但各相含量有差别。而淬火态和淬火+一次回火态的渗氮试样未能获得具有足够好综合性能的渗层组织。     

显微组织对WCu触头材料电弧特性及抗烧蚀性能的影响

采用两种不同的真空熔渗工艺制备了W80Cu20触头材料,分析了两种合金的显微组织,测定了两种合金的成分、密度、电导率、硬度和抗弯强度。对两种合金进行了真空电弧击穿试验和SF6断路器型式试验,测量其真空击穿时的截流值和击穿场强,分析了触头材料电弧烧蚀后的表面形貌,比较了两种合金的抗电弧烧蚀能力。结果表明,两步法烧骨架熔渗工艺制备的WCu合金显微组织均匀,铜相平均尺寸为4~6μm;一步法熔渗工艺制备的WCu合金中的铜相大小不一致,存在带状铜相聚集体,其最大尺寸可达80~100μm。两步法工艺制备的WCu合金的硬度、抗弯强度高于一步法制备的合金,真空击穿场强及截流值稳定,其耐电弧烧蚀能力明显高于一步法制备的合金。     

热处理工艺对18%Cr马氏体不锈钢组织与力学性能的影响

以羰基Fe粉以及Cr_3C_2,VC,Mo_2C等碳化物粉末为原料,制备Cr含量(质量分数,下同)为18%的粉末冶金马氏体不锈钢。将不锈钢分别在1 050℃和1 150℃下淬火,然后于200~590℃下进行回火处理,研究热处理工艺对不锈钢组织与力学性能的影响。结果表明:粉末冶金18%Cr马氏体不锈钢的基体中存在M_7C_3型以及MC型碳化物,随回火温度升高,碳化物数量增多并且碳化物形态由原来的部分连续状向孤立、块状转变。1 150℃温度下淬火的不锈钢,其硬度较高,HRC最高达63.9,在较低温度下(200℃)回火时,抗弯强度为2 002 MPa,而在530℃温度下回火后,抗弯强度大幅升高至3 093 MPa。1 150℃淬火的不锈钢,其冲击韧性较低,随回火温度升高而升高。热处理后的不锈钢断裂形式均为准解理断裂。     

淬火温度对高碳钢组织和断裂韧度的影响

研究了不同淬火温度对高碳钢组织及断裂韧度的影响。利用紧凑拉伸试样测量其平面应变断裂韧度,扫描电镜(SEM)观察淬回火后的组织演变规律及断裂韧度试样断口形貌。结果表明:随着淬火温度的升高,淬火态组织中残余碳化物数量逐渐减少至920℃时全部消失;晶粒尺寸在淬火温度大于960℃时明显长大。600℃高温回火后,组织由残留大碳化物颗粒、回火析出碳化物及铁素体基体组成;塑性单调下降;断裂韧度在小于960℃时单调下降,大于960℃后基本不变;KIC试验断口逐渐由准解理型断裂转变为沿晶断裂。塑性变化是试验钢韧性降低的主要原因。     

喷射成形2060高速钢的组织与性能

利用雾化沉积炉制备喷射成形2060高速钢沉积坯,经过锻造后再进行盐浴淬火和回火处理,研究喷射成形2060高速钢及其热处理后的组织与力学性能。结果表明:喷射成形2060高速钢沉积坯的表面较光洁,无明显的宏观偏析,晶粒较细小,晶粒尺寸约为20μm,沉积坯的相对密度在99.5%以上;沉积坯中主要存在M6C和MC两种碳化物相,均匀弥散分布在晶界与晶内以及基体中,氧含量只有1.6×10-7左右。2060高速钢的抗弯强度随淬火温度升高而逐渐降低,淬火温度应低于1 210℃。在1 170~1 190℃下淬火时可获得抗弯强度≥3 000MPa、硬度≥70 HRC的良好综合力学性能。     

铜包覆石墨烯增强316L奥氏体不锈钢力学性能研究

采用分子水平混合和低速球磨的方法制备铜包裹石墨烯/316 L不锈钢复合粉体,通过放电等离子烧结制备石墨烯增强316 L奥氏体不锈钢复合材料,研究铜及石墨烯对复合材料密度、硬度和拉伸性能的影响,并对拉伸断口形貌进行了分析.结果表明:通过分子混合和球磨混合可制备铜包裹石墨烯与不锈钢均匀混合的复合粉体.烧结过程石墨烯结构保持完整.铜包裹石墨烯增强体可明显改善烧结不锈钢复合材料的密度、硬度、抗拉强度和屈服强度,使其分别提高3.6%、17.4%、35.8%和34.5%.     

硅黄铜预合金粉末在金刚石工具中的应用

采用气水耦合雾化法制备了含有质量分数0.4%稀土Ce的硅黄铜预合金粉末, 在680~720 ℃热压烧结预合金粉末, 获得了致密烧结体。通过洛氏硬度计测试烧结体硬度为HRB62~65, 使用万能力学实验机测试烧结体抗弯强度为530~550 MPa, 利用扫描电子显微镜观察烧结体基体微观组织为α相黄铜, 组织中还存在蠕虫状及花状的弥散银灰色(β'+γ)相。选择添加质量分数20%的硅黄铜预合金粉末配方(铁粉+铜粉+锌粉+预合金粉末)制备花岗岩切割用金刚石刀头, 与单质粉末混合配方(铁粉+铜粉+锌粉)制备的刀头相比, 添加硅黄铜预合金粉末的刀头硬度增加22%, 抗弯强度降低8%, 刀头锋利度和使用寿命整体提升, 胎体磨粒夹杂减少, 并出现大量排屑沟槽。     

还原铁粉对Fe-1.1Ni-0.5Mo-0.5Cr合金组织与性能的影响

在惰性气体雾化法制备的Fe-1.1Ni-0.5Mo-0.5Cr预合金粉末中添加1.5％的Cu粉和0.6％的C粉(均为质量分数)以及还原铁粉(添加量分别为0、10％、20％和30％),混合均匀后在600 MPa压力下模压,在1 180℃烧结1h.烧结合金经180℃/1h回火处理后,进行密度、硬度、拉伸力学性能检测以及显微...     

合金元素对汽车减震器活塞组织与性能的影响

为了将轴承滚动体研磨钢泥制得的还原铁粉应用于汽车减震器活塞的生产中,在其中加入石墨、电解铜粉及羰基铁粉等制成合金粉末,并压制、烧结成型,通过正交试验探讨石墨、电解铜粉及羰基铁粉质量分数对试样组织和性能的影响。结果表明,碳对硬度和抗拉强度的影响最大,铜的影响较小;随石墨和铜粉质量分数的增大,铁素体减少,珠光体增多;得出成分为Fe-1.2C-1.8Cu-10羰基铁粉的合金符合汽车减震器铁基粉末冶金零件技术条件JB/T 9138-1999的要求。     

Effect of copper infiltration on fracture mode in sintered steels

Abstract

The fracture mode of PM steels depends on features, such as pores, densification, diffusion of any added alloying elements, contact area between particles, microstructural homogeneity, and applied load conditions. Consequently, when a sintered steel is infiltrated, several factors that determine the fracture behaviour are affected. The density is raised (in absolute terms, because the infiltrant is usually of higher density, and in relative terms, because activated sintering is promoted by permanent liquid phase sintering). The liquid phase promotes a rounding of the pores which enhances stress transmission from the necks to the particles. Sintered steel with 0˙6%C was infiltrated with three amounts of copper to study the influences of the amount of infiltration and the resultant final density on the fracture mode. Specimens were first uniaxially pressed to 7˙0 g cm^–3 green density, then sintered and infiltrated simultaneously at 1120°C in a 90N₂–10H₂ atmosphere. The mechanical results and microstructures were analysed to evaluate the fracture behaviour and fracture surfaces. The mechanical behaviour was characterised by hardness, tensile and three point bending tests.     

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The stainless steel/iron chips core cladding bar was hot-rolled by using recycling iron scrap. The interface of the metals and the influence of rolling pass, rolling temperature, graphite additive on properties of stainless steel/iron chips core cladding bar were analyzed by optical microscope, SEM, EDS and micro hardness tester. The experimental results show that element diffusion occurs at the interface after six passes rolling and the width of diffusion zone is about 70-80??m. The Fe of carbon steel diffuses into stainless steel and the Cr, Ni, Mn of stainless steel diffuse into carbon steel which makes micro hardness of carbon steel near the interface increase obviously. The bonding strength between stainless steel and iron chips core increases with increasing of rolling passes and it is 355MPa after six passes rolling. The tensile strength and elongation of the cladding bar increase with increasing of rolling temperature and they are 470MPa and 32% at 1150??, 500MPa and 35% at 1250??. The composition of iron chips core is improved by adding graphite powder. With the increasing of the graphite in iron chips, the tensile strength of cladding bar increase, but decrease for elongation. White reticular secondary cementite is appearing when the graphite is 1. 0% and the tensile strength is up to 736. 5MPa, the elongation decrease to 16%. The tensile fracture shows brittle fracture morphology.     

Strength of Unsintered Powder Compacts with Axial and Radial Loading

Cohesion and the internal friction angle characterizing the fracture region for the contour of Drucker-Prager limiting states are determined by experiment for green copper and iron powder compacts. With an increase in density the increase in cohesion is more marked for iron compacts. With an increase in compaction density the internal friction angle increases from 67° to 70° for copper compacts and it decreases from 70.5° to 69.9° for iron powder specimens.     

粉末冶金法制备CrFeNiCuMoCo高熵合金的组织与性能

利用粉末冶金法制备CrFeNiCuMoCo高熵合金,用带有能谱的扫描电子显微镜(SEM/EDS)、X射线衍射仪、显微/维氏硬度计、电化学工作站、材料试验机等对CrFeNiCuMoCo高熵合金组织结构进行分析并测试其硬度、耐蚀性和压缩性能.结果表明:CrFeNiCuMoCo高熵合金组织形貌简单;物相主要由FCC和BCC两相组成,Mo元素和Cu元素在合金中存在偏析现象;合金的耐蚀性能优异,与304不锈钢相比,自腐蚀电流密度减小1个数量级;组元间原子半径的差异导致较大的晶格畸变,阻碍位错的运动,使得固溶强化效应增强;Mo元素起到细化晶粒作用,使该合金具有较高的硬度和抗压强度,合金硬度为485 HV,抗压强度约为1 385MPa;断裂类型为脆性解理断裂.     

Effects of chromium sources on the microstructure and properties of TiC-steel composites

The composites of low alloy steel reinforced with TiC particles (36?wt-%) were prepared by conventional powder metallurgy process in this paper. The chromium in the steel matrix was provided by pure chromium powder (PCP), low carbon ferrochrome powder, medium carbon ferrochrome powder (MCFP) and high carbon ferrochrome powder. The SEM was used to observe the particle morphology and microstructure. Density, hardness and transverse rupture strength (TRS) of the samples were tested. The results show that the composite prepared with the PCP as a chromium source has low hardness and TRS and the composites prepared with different ferrochrome powders have higher hardness and TRS. The microstructures of the samples prepared with different chromium sources have some differences and provide the differences in mechanical properties and fracture morphology. The sample prepared with the MCFP as chromium source has the highest comprehensive performance after tempering: hardness 70 HRC and TRS 1752?MPa.     

OBSERVATIONS ON THE SINTERING OF COMPACTSFROM A MIXTURE OF IRON AND COPPER POWDERS

Abstract

Three grades of iron powder-an atomized steel powder, a sponge iron powder reduced from magnetite with carbon, and a powder reduced from mill scale with hydrogen were mixed with 3% of copper powder and pressed into compacts. The diametral dimensional changes of the compacts during sintering below and above the melting point of copper were measured, their microstructures examined, and both related to the characteristics of the powders, particularly their specific surface. During sintering below the melting point of copper, compacts of all three powders shrank. Micrographic examination showed that the copper is transported by solid-state diffusion along the surfacesand grain boundaries of the iron powder particles. During sintering above the melting point of copper, compacts of the atomized and the MH-100 sponge iron powders grew while those of the hydrogen reduced mill-scale powder shrank. This phenomenon is related to the different mode of penetration of liquid copper in the compacts from the three powders, observed in the microstructures of the compacts.