铁基粉末冶金材料多元共渗层的摩擦与磨损

研究了不同成分及密度的铁基粉末冶金材料经多元共渗后渗层的摩擦与磨损特怀及金相组织，结果表明，经共渗处理后，低密度的铁基粉末冶金材料的耐磨性能优于高密度的铁基粉末冶金材料，且摩擦力矩小，摩擦系数低。     

稀土La对35钢盐浴碳氮共渗涂层结构与性能的影响

在由氰酸盐(KCNO和NaCNO)与碳酸盐(K2CO3和Na2CO3)组成的盐浴中添加适量稀土La,对35钢材料进行盐浴碳氮共渗,对涂层的显微组织、涂层的厚度、显微硬度沿层深的分布以及涂层的耐磨性进行测试与分析,研究稀土La对35钢盐浴碳氮共渗的影响。结果表明:在盐浴中添加稀土La可显著提高碳氮共渗层的厚度和表面硬度;在温度为560℃、时间为2 h条件下进行盐浴碳氮共渗时,添加稀土La可增加化合物层的厚度,稀土添加量(质量分数)为5%时化合物层最厚;添加稀土还可提高涂层硬度,在575℃/2 h、添加5%稀土条件下盐浴碳氮共渗后,试样表层硬度HV0.01达到最大值835,且耐磨性显著提高,与常规盐浴碳氮共渗相比,质量磨损降低38.4%。     

稀土对低温固体B-C-N共渗的影响

本文研究了硼－碳－氮－稀土（Ｂ－Ｃ－Ｎ－ＲＥ）共渗工艺及共渗层的组织性能，并与硼－碳－氮（Ｂ－Ｃ－Ｎ）共渗工艺及共渗层的组织性能进行了比较，结果表明，在适当范围内，稀土具有明显的催渗作用；与Ｂ－Ｃ－Ｎ共渗相比，Ｂ－Ｃ－Ｎ－ＲＥ共渗层的耐磨性和耐蚀性明显提高。本文对Ｂ－Ｃ－Ｎ－ＲＥ共渗的机理及稀土元素的作用作了初步的探讨。     

45钢滴注式气体碳硼稀土共渗的研究

采用滴注式气体化学热处理方法对４５钢进行了表面强化的研究。在温度、时间、煤油滴量均相同的条件下，采用碳稀土共渗、碳硼稀土共渗和常规单纯渗碳３种工艺，从金相组织、渗层厚度和显微硬度的分布三方面作了对比试验，结果表明，碳硼稀土共渗试样的渗层度高于碳稀土共渗与单纯渗碳，以深度显著大于单纯渗碳，稍低于碳稀土共渗，显示了的催渗作用，同时试验了稀土加入量与渗层深度伯关系，找出稀土垢最佳加入量。     

《辉光离子氧—硫—氮三元共渗工艺的试验研究》

本文阐述了用NH_3和SO_2进行辉光离子氧—硫—氮三元共渗工艺的试验研究。试样材料选用45~#钢、Cr_(12)MoV、3Cr_2W_8等。对共渗后的试样进行了渗层的组织分析和表面状态观察;用X—射线测定了渗层的相结构。用电子探针分析了共渗试样的表层成分;测量了渗层的显微硬度;讨论了不同流量比、温度、时间对渗层组织和渗层厚度的影响。结果表明:离子S—N—O共渗,其共渗温度:450—570℃,时间1～6h,先氮化后共渗,共渗后可以得到满意的共渗效果。     

烧结锰钢碳氮共渗层结构的研究

用TEM研究了粉末烧结Fe—C系和Fe—Mn—C系合金碳氮共渗层的组织结构。结果表明,锰能增加烧结体的开口孔隙度,从而增加共渗层深度。经150℃回火,碳氮共渗马氏体中析出Fe_(18)N_2(α″)相,合金元素锰能显著增加Fe_(16)N_2(α″)相的弥散度。经300℃回火,碳氮共渗马氏体中析出Fe_3C,没有发现Fe_4N(γ′)相。     

碳氮共渗粉末锻造钢的表面摩擦磨损性能

原料粉末为Hoganas ATST-D,添加石墨粉以调整锻坯的最终碳含量。在控制气氛和1100℃进行热锻。将热锻件进行热处理,产生回火马氏体和贝氏体组织。进行碳氮共渗处理,其显微组织变化不明显,试样表面形成15μm厚的白色     

离子硫,氮,碳稀土多元共渗

对热挤压模具钢3Cr2W8V进行了基体强韧化处理以及表面离子硫、氮、碳加稀土共渗处理,分析其基体组织及表面层组织,进行了耐磨性试验。结果表明,加入稀土可有效地提高扩渗速度及渗层质量。由于表面形成了一层Fe_2S,在热挤压过程中有自润滑作用,从而大幅度提高了模具的耐磨性,显著增加使用寿命。     

稀土对模具钢钒硼共渗层组织和性能的影响

本文研究了模具钢盐浴钒硼共渗工艺中，添加适量稀土对共渗层组织和性能的影响。并探讨了稀土元素对共渗层催渗作用机理，以及盐浴稀土钒硼共渗工艺在模具表面强化处理中的实际应用。应用结果表明，冷作模具经盐浴稀土钒硼共渗处理后比常规热处理的模具使用寿命提高３～７倍。     

硼碳共渗—低温渗硫复合处理在热冲模上的应用

本文介绍了用简易的夹具对热冲模具进行固体硼碳共渗处理,并在共渗层的表面施以渗硫的尝试。结果表明,热冲模具经硼碳共渗及基体强化处理后再渗硫复合处理工艺,可提高模具寿命三倍,经济效益显著。     

Effect of C/N Concentration Fluctuation on Formation of Plasma Electrolytic Carbonitriding Coating on Q235

 The plasma electrolytic carbonitriding (PEC/N) on the Q235 steel was investigated in an aqueous solution containing monoethanolamine and KCl in a very short period of time. The microdischarge characteristics of the voltage/current on the Q235 were observed using real-time imaging during the PEC/N. The microstructure and element distribution of the carbonitriding layer were examined using scanning electron microscope (SEM) equipped with energy dispersive spectroscope (EDS). The effect of microdischarge on roughness, thickness and microhardness was evaluated. The formation of the carbonitriding layer was discussed. Research shows that it is similar in the microstructure and properties between the plasma electrolytic carbonitriding and the traditional gas carbonitriding. The formation of the carbonitriding layer results from the carbon and nitrogen fluctuation in PEC/N process. The microhardness and thickness can be up to HV 779 and 0.360 mm in 180 s, respectively, which is close to the results of the gas carbonitriding in the microhardness. Therefore, the plasma electrolytic carbonitriding has a potential to substitute the gas carbonitriding.     

Roentgenographic Determination of Residual Stresses in Carbonitrided Layers

The aim of the current investigation is to examine the influence of carbonitriding in low-temperature plasma on forming macroresidual stresses in the surface layer of the materials. Particular modes of ion carbonitriding are considered in which layers of different depth and different surface microhardness are obtained. The residual stresses in the α-Fe in carbonitride layers are determined by the method of “sin²Ψ.” The results show that at different modes of ion carbonitriding, residual macrostresses are obtained that have different values and depend on the qualitative characteristics of the formed carbonitrided layers.     

A REVIEW OF SINTERED METAL BEARINGS: THEIR PRODUCTION,PROPERTIES, AND PERFORMANCE

Abstract

Five classes of sinter-based bearings are identified: steel-backed materials with compacted non-porous sintered linings for engine bearings and wrapped bushes; steel-backed materials with porous sintered linings impregnated with a plastic, intended for operation dry or with sparse lubrication; unbacked porous sintered-metal parts impregnated with oil to form self-lubricating bearings; unbacked non-porous sintered metal parts incorporating graphite; sintered polytetrafluoroethylene parts incorporating powdered metals. Methods of manufacture are outlined.

Techniques of bearing evaluation are described, the most useful being sophisticated, flexible test-rigs which approach closely the conditions of actual bearing applications.

The relative fatigue strengths of sintered engine-bearing linings are given and sintered copper-lead is shown to be equivalent in fatigue strength to cast linings.

The impregnation of sintered bronze linings with PTFE and lead yields a material with good un lubricated wear-resistance. The effect of load, rubbing speed, and other variables is described. A polyacetal lining bonded to a steel backing via a porous bronze interlayer gives a bearing material with good performance under conditions of sparse lubrication.

The relative merits of oil-impregnated porous metal bearings obtained by the pressing and sintering of copper, iron, or aluminium alloy powders are described. For optimum performance the bearing conditions should favour the formation of a hydrodynamic film of oil over the bearing surface.

The incorporation of graphite into fully compacted powder-metallurgy parts gives improved wear-resistance under dry and sparsely lubricated rubbing conditions.

PTFE parts incorporating metal powders can be moulded to finished size by powder-metallurgy techniques.     

H13模具钢表面处理和热疲-热熔损性能

对H13钢进行了硫氮碳（SNC）共渗加氢化处理、稀土（RE）-SNC共渗及稀土（RE）－SNC共渗加氧化处理等表面处理工艺试验；并对处理试样分别进行了热疲劳性能和在合金铝液中的热熔损性能试验；结果表明，在空气氧化条件下，添加稀土的SNC共渗加氧化复合处理试验的渗层热疲劳性能比未添加稀土（RE）的SNC共渗加氧化复合处理及随后未经氧化处理的RE-SNC共渗的试样高；在本试验条件下，加稀土进行处理的试样比未加稀土进行处理的试样，在铝液中的热熔损性能略偏低。     

Simultaneous plasma treatment for carburizing and carbonitriding using hollow cathode discharge

Ion carburizing and nitriding are effective processes for saving energy and providing polutionless surface treatment but have the disadvantage of using much electric energy. A cylindric subsidiary cathode was set up around a rod-shaped workpiece with a gap, and hollow cathode discharge for ion carburizing was studied. Thus, simultaneous plasma treatments for ion carburizing and ion car-bonitriding in one workpiece were researched using Cr-Mo steel to save electric treatment power. First, the effects of the gap between the test piece and subsidiary cathode and the pressure of electric discharge gas, including methane gas, on fundamental plasma treatment conditions were experimen-tally researched. It was found that the temperature for ion carburizing in a H₂-N₂-Ar-CH₄ gas mixture was 1123 to 1193 K with a gap of 3 to 5 mm under a gas pressure of 133 to 532 Pa. Next, the test piece was ion carburized with hollow cathode discharge and carbonitrided with normal glow dis-charge simultaneously. The ion-carburized layer was formed in the area covered by the subsidiary cathode. The surface hardness was 800 Hv, the effective case depth was 0.6 mm, and the surface carbon content was 0.75 wt pct. An ion carbonitriding layer was formed in the area without the subsidiary cathode. The surface hardness was 700 Hv and the case depth was 0.1 mm. It is useful to form the different layers of ion carburizing and ion carbonitriding in one treatment process and to give different mechanical and tribological properties on one workpiece simultaneously.     

Study of bipolar pulsed nanocrystalline plasma electrolytic carbonitriding on nanostructure of compound layer

Surface hardening of commercially pure titanium by using bipolar pulsed nanocrystalline plasma electrolytic carbonitriding was studied in this investigation. The coating process was performed on triethanolamine-based electrolyte by a cooling bath. The nanostructure of the obtained compound layer was examined with figure analysis of SEM nanographs. The effects of process variables, i.e., triethanolamine concentration, electrical conductivity of electrolyte, applied voltage, and treatment time, have been experimentally studied. Statistical methods were used to achieve the optimum size of nanocrystals. Finally, the contribution percentage of effective factors of pulsed current was revealed and confirmation runs showed the validity of the obtained results. The text was submitted by the authors in English.     

A METALLOGRAPHIC TECHNIQUE for FERRITES

Abstract

A technique is described for the rapid preparation of ferrite specimens for metallographic examination by means of polytetrafluorethylene polishing laps impregnated with diamond.     

20钢纺织钢领无毒盐浴C N RE共渗研究

 用55%KCl+45%NaCl作为基础盐，以“603”无毒液体渗碳剂添加适量的NH4Cl和微量的镧系氯化稀土等均匀混合后制成“混合渗剂”，首先在实验室内对20钢纺织钢领进行了不同温度和时间的C N RE共渗试验。对试验结果进行了表面质量、变形、硬度、金相和剥层分析后，优化出工艺参数，即在860 ℃下共渗25 h后直接淬火，再于140~150 ℃下低温回火15 h。随后，在重庆润丰纺织机械公司热处理车间进行了中试，将中试产品用于上车试验，取得了成功。最后，在100 kW中温盐浴炉上对该产品投入了批量生产。从而，淘汰了原来的气体渗碳后缓冷，再用70%NaCN+30%NaCl盐浴重新加热淬火并进行140~150 ℃低温回火的较为繁琐、不经济和有剧毒的工艺制度。     

Magnetic Microstructures of 2:17 Type Sm(Co,Fe,Cu,Zr)z Magnets Detected by Magnetic Force Microscopy

The magnetic microstructures of 2:17 type Sm(Co,Fe,Cu,Zr)z magnets were detected by magnetic force microscopy.Comparing the microstructures of the specimens coated with and without Ta thin film before and after heat-treatment, it is found that: (a) as a protection layer, Ta coating layer about 20 nm thick can effectively restrain Sm volatilization under high temperature;(b) the stress built in the 2:17 type Sm-Co magnets during specimen preparation only affects some local parts of the domain structures;(c) the magnetic microstructures vary largely for specimens heat-treated at high temperature without Ta film coating due to Sm volatilization.In addition, by comparing with high coercivity Fe-Pt point tips, it is found that the Co-Cr thin-film tips are not suitable for detecting the magnetic microstructures of strong permanent magnets.