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1.
Yu. M. Lakhtin G. N. Neustroev N. I. Sologubova L. P. Frolova 《Metal Science and Heat Treatment》1987,29(5):359-364
Conclusion Carbonitriding at 700°C in a mixture of 70–30% of ammonia and 30–70% of endogas (or natural gas) is recommended for the production of a diffusion layer with a good set of operational properties (for example, with high wear resistance).Moreover, the use of a gaseous atmosphere based on commercial nitrogen (50–90%) with ammonia, natural-gas, oxygen, or carbon dioxide additives is promising for carbonitriding at 700°C. Here, this medium should not contain more 0.5–1.0% of O2 and 3% of CO2. The nitrogen-based gaseous atmospheres ensure the attainment of quality diffusion layers with decreased risk of explosion and saving of energy resources.Moscow Automobile Traffic and Highway Construction Institute. Nongovernmental Production Union "All-Union Scientific-Research and Experimental Design Institute for Trade Machine Construction. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 32–36, May, 1987. 相似文献
2.
1. | Carbonitriding at 700°C in atmospheres of ammonia and carbon-containing components (endogas or natural gas) makes it possible to obtain a high-quality carbonitride (oxycarbonitride) case containing 3–4% N in the dense zone and 0.5–1% in the porous zone 0.5–1.0% C, and up to 3.5% 0, an austenitic-martensitic sublayer containing 1.0–0.6% N and C and 0 at the level of the matrix, and a lower-lying layer of a solid solution of nitrogen in -Fe. |
2. | Carbonitriding at 700°C promotes a significant increase in wear resistance of constructional steels. In this case the coefficient of sliding fraction in tests without lubricant was 0.20–0.23, the fatigue limit in bending increases by 1.7 times in comparison with the normalized condition, and the corrosion resistance increases by an average of 10 times. |
3.
E. N. Druzhinina A. V. Lakedemonskii Yu. E. Abramenko B. V. Lugovtseva 《Metal Science and Heat Treatment》1968,9(7):540-542
Conclusions We recommend the following heat treatment for the cylinder sleeves of certain tractor and automobile engines; it ensures a high wear resistance and does not induce warping: a) annealing for stress relief, with heating at 75–100 deg/h to 580–600°C, soaking, cooling at the rate of 40–50 deg/h to 200°C; final machining, including honing; b) gas cyaniding 6 h at 560–580°C in a medium of 70% carburizing gas and 30% ammonia.Bauman MVTU, Moscow Automobile Plant. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 60–62, July, 1967. 相似文献
4.
S.Y. Chang L.C. TsaoY.H. Lei S.M. MaoC.H. Huang 《Journal of Materials Processing Technology》2012,212(1):8-14
Al-8.4Si-20Cu-10Ge and mixed rare-earth elements (Re) containing Al-8.4Si-20Cu-10Ge-0.1Re filler metals were used for brazing of 6061 aluminum alloy/Ti-6Al-4V. The addition of 20 wt.% copper and 10 wt.% germanium into the Al-12Si filler metal lowered the solidus temperature from 586 °C to 489 °C and the liquidus temperature from 592 °C to 513 °C. The addition of 0.1 wt.% rare-earth elements into Al-8.4Si-20Cu-10Ge alloy caused remarkable Al-rich phase refinement and transformed the needle-like Al2Cu intermetallic compounds into block-like shapes. Shear strengths of the 6061 aluminum alloy/Ti-6Al-4V joints with the two brazing filler metals, Al-8.4Si-20Cu-10Ge and Al-8.4Si-20Cu-10Ge-0.1Re, varied insignificantly with brazing periods of 10-60 min. The average shear strength of the 6061 aluminum alloy/Ti-6Al-4V joints brazed with Al-8.4Si-20Cu-10Ge at 530 °C was about 20 MPa. Rare-earth elements appeared to improve the reaction of the Al-8.4Si-20Cu-10Ge filler metal with Ti-6Al-4V. The joint shear strength of the 6061 aluminum alloy/Ti-6Al-4V with Al-8.4Si-20Cu-10Ge-0.1Re reached about 51 MPa. 相似文献
5.
天然气中硫的超标不但会使制取吸热式气氛的镍基催化剂中毒失效,同时还影响渗碳的界面反应,降低零件的表面硬度,延长渗碳时间。所以作为渗碳用原料气必须对天然气充分脱硫。 相似文献
6.
Galvalume (trademark of Bethlehem Steel Corp.) sheet steel samples were heated in pure oxygen and 97% O2/3% H2O atmospheres at temperatures ranging from 300 to 670°C. Time at a particular temperature was varied but did not exceed 48 hr. Above 480°C, the Galvalume coating became rapidly alloyed with iron to form Al13Fe4, and zinc was lost by vaporization. The Zn content dropped to about 15 wt%. The time required to fully alloy the overlay at 490°C was less than 4 hr. Below 480°C, only minor microstructural changes occurred, and coating integrity was maintained. No differences in behavior were observed by the addition of 3% water vapor to the gas stream. 相似文献
7.
Results of a study of saturation of steel 20Kh with carbon in an endothermic atmosphere with an additive of natural gas and ammonia under the conditions of cyclic temperature changes within 900 650°C are presented. It is shown experimentally that it is possible to form martensite and martensite-carbide structures in the diffusion layer depending on the process parameters. The distribution of carbon over the thickness of the diffusion layer is calculated. 相似文献
8.
V. Medri 《Corrosion Science》2003,45(11):2525-2539
The corrosion behaviour of an electroconductive Si3N4-35 vol% TiN composite, hot pressed with the addition of Al2O3 and Y2O3 as sintering aids, was studied in 1.8 M sulphuric acid aqueous solution at RT, 40 and 70 °C up to 400 h. The corrosion follows linear kinetics at RT and at 40 °C, involving only the progressive chemical dissolution of grain boundary phases, in the system Al-Y-Si-Ti-O-N. Chemical attack of TiN occurs at 70 °C, while Si3N4 is not affected by the selected corrosive environment.The effect of the corrosion on flexural strength, fracture toughness and electrical resistivity were investigated. Very high strength levels are maintained after corrosion for 400 h at room temperature, while the strength decreases of about 10% and 16% after the treatment at 40 and 70 °C, respectively. The electrical resistivity rises after corrosion at 40 and 70 °C, in line with the progressive chemical dissolution of the conductive TiN particles. 相似文献
9.
Ruchuan Yin 《Corrosion Science》2005,47(8):1896-1910
Carburization of 310 stainless steel has been investigated after cyclic exposures at high temperatures 800-1100 °C in a 2%CH4/H2 carburizing gas mixture for 500 h duration. A thermodynamic analysis indicates that 1000 °C is an approximate boundary temperature, below which the environment should result in mixed oxidizing/carburizing behavior, while above this temperature reducing/carburizing behavior should occur. The experimental results agree well with the thermodynamic analysis. Below 1000 °C, 310SS suffered external carburization, oxidation, and internal carburization. In excess of 1000 °C, extensive external carburization occurred and internal Cr-carbides disappeared. Cr segregation is proposed to interpret the effect of temperature on the continuity of an external scale layer and carburization behavior. 相似文献
10.
1. | Microadditions of Y and La to multialloyed type AL4 alloys influence the temperature ranges of passage of individual stages without changing the character of the hardening and aging processes. |
2. | A shortened heat treat cycle in the solid state for multialloyed AL4+Sb+Sr+Y alloy including homogenization at 535±5°C for 4–6 h, water hardening, and aging at 175±5°C C for 4 h has been developed. |
3. | For AL4+Sb+Sr+La alloy the maximum strength and plastic properties are obtained after heat treatment by homogenization at 520±5°C for 4–6 h, water hardening, and aging at 175±5°C for 4 h. |
4. | The heat treat cycles developed for multialloyed silumins provide an increase in their strength, plasticity, and corrosion resistance as the result of increasing the degree of differentiation of the phases and structural constituents and also redistribution of impurities. In addition, the stability of the alloy properties is increased. |
11.
Titanium was powder siliconized and gas nitrided, in order to improve its cyclic-oxidation resistance. Siliconizing was performed in a pure-silicon powder at temperatures in the range of 800–1100° C for 3–48 h. Gas nitriding was carried out in pure N2 at 1100° C/12 h. Cyclic-oxidation experiments with the siliconized and nitrided samples were conducted in air at 850 and 950° C for up to 560 h. It was found that the siliconized layers grew according to the parabolic law with the activation energy for siliconizing ES being 47.2 kJ mol–1. Powder siliconizing at 900–1100° C/3 h produced multi-phase layers, in which Ti5Si3 silicide predominated The siliconizing temperature of 800° C/3 h appeared to be insufficient, because it led to a non-uniform surface layer with a slight protective effect. The nitrided layers were composed of titanium nitride TiN and -Ti(N) intestitial solid solution. Measurement of the oxidation kinetics revealed that the titanium siliconized at 900–1100° C/3 h oxidized much more slowly than pure Ti, Ti–6Al–4V alloy and nitrided titanium. Microstructural investigation revealed the complex sub-structure of the scales on the siliconized samples which was composed of rutile+silica, rutile and nitrogen-rich sub-layers. The mechanism of high-temperature cyclic oxidation of the siliconized and nitrided titanium is discussed. 相似文献
12.
Xiaoli Xi Xiangyang XuZuoren Nie Shan HeWei Wang Jie YiZuo Tieyong 《International Journal of Refractory Metals and Hard Materials》2010
W–Cu composite materials have been widely used in heat sink apparatus and as electronic packaging materials. The preparation of the materials, especially the synthesis of W–Cu nanopowder, is a subject much more researches on. This paper focuses on the synthesis of W–Cu composite nanopowder using the freeze-drying technique, an environment-friendly and advanced technique for powder manufacturing. The process involved mixing ammonium metatungstate with CuSO4·5H2O as preliminary liquid solution and the use of liquid nitrogen as a cryogenic media; W–5Cu, W–10Cu and W–20Cu composite nanopowders were obtained after vacuum drying and following thermal decomposition reduction. X-ray diffraction, infrared spectroscopy and field emission scanning electron microscopy were used to characterize these nanopowders. The results showed that the freeze-drying precursor was the amorphous matter containing tungstate, sulfate, crystal water and ammonia. Copper appeared at 200 °C, tungsten and β-tungsten could not be obtained until 500 °C, and pure tungsten was found above 700 °C, which meant that the whole reduction process was completed. Crystallized W–Cu composite nanopowder, with particle sizes of 10–20 nm, was produced via a two-stage reduction: 400 °C for 2 h and then 700 °C for 2 h. 相似文献
13.
R.V. Mangalaraja S. AnanthakumarM. Paulraj H. PesentiMarta López Carlos P. CamurriLoreto A. Barcos Ricardo E. Avila 《Journal of Alloys and Compounds》2012,510(1):134-140
Nanocrystalline samarium doped ceria electrolyte [Ce0.9Sm0.1O1.95] was synthesized by citrate gel combustion technique involving mixtures of cerium nitrate oxidizer (O) and citric acid fuel (F) taken in the ratio of O/F = 1. The as-combusted precursors were calcined at 700 °C/2 h to obtain fully crystalline ceria nano particles. It was further made into cylindrical pellets by compaction and sintered at 1200 °C with different soaking periods of 2, 4 and 6 h. The sintered ceria was characterized for the microstructures, electrical conductivity, thermal conductivity and thermal diffusivity properties. In addition, the combustion derived ceria powder was also analysed for the crystallinity, BET surface area, particle size and powder morphology. Sintered ceria samples attained nearly 98% of the theoretical density at 1200 °C/6 h. The sintered microstructures exhibit dense ceria grains of size less than 500 nm. The electrical conductivity measurements showed the conductivity value of the order of 10−2 S cm−1 at 600 °C with activation energy of 0.84 eV between the temperatures 100 and 650 °C for ceria samples sintered at 1200 °C for 6 h. The room temperature thermal diffusivity and thermal conductivity values were determined as 0.5 × 10−6 m2 s−1 and 1.2 W m−1 K−1, respectively. 相似文献
14.
ZhS6KP alloy is used in commercial production of blades of aircraft engines pressed in Widin presses. Standard heat treatment that consists in air hardening from 1220°C (4 h) and aging at 950°C for 2 h with cooling in air does not always provide an optimum combination of long-term strength and fatigue resistance for the alloy at 900°C. In this connection, the possibility of improving the fatigue resistance and the long-term strength while preserving the high level of short-term mechanical properties by conducting low-rate plastic deformation before the heat treatment is considered.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 31 – 33, July, 1996. 相似文献
15.
Turbines fired with hydrogen or syngas from coal gasification will have significantly higher water vapor contents in the combustion gas than natural gas fired turbines. The effect of increased water vapor on alumina-forming coatings and model alloys was investigated at 1100 °C in furnace cyclic testing. Increasing the water vapor content from 10% to 50 vol.% increased the amount of scale spallation on undoped alumina-forming alloys. Compared to dry O2, increased spallation was observed for β and γ/γ' phase coatings on the substrates of alloys 142 and N5. In all cases, the addition of water vapor appeared to reduce the formation of alumina whiskers and ridges at the scale-gas interface, but did not significantly change the alumina growth rate. The addition of water vapor may have a detrimental effect on the selective oxidation of Al in γ/γ' alloys and coatings. 相似文献
16.
The sulfur activity-composition relation of -Ni3±xS2 was determined between 600 and 750°C by thermogravimetry using H2S/H2 gas mixtures. The existence of 1- and 2-Ni3±xS2 was confirmed. The chemical diffusion coefficient of -Ni3±xS2 was measured as a function of composition at 650°, 700°, and 750°C using thermogravimetry for the reequilibration reaction. The chemical diffusion coefficients varied with composition and showed a maximum at stoichiometric composition, Ni3S2. The activation energy for chemical diffusion was determined as Ea=31.3 Kcal·mole–1 for stoichiometric Ni3S2. Electrical conductivity of -Ni3+-xS2 was determined as a function of composition at 650°C. The electrical conductivity increased with increasing the mole fraction of sulfur. The temperature dependence of the electrical conductivity of Ni3S2 was measured between 50 and 750°C and found to exhibit metallic behavior. 相似文献
17.
P. Kochmanski 《Surface & coatings technology》2008,202(19):4834-4838
Results of the investigation of nitrided layers on 17-4 PH type precipitation hardening stainless steel are presented in this paper. The layers have been produced in the process of gas nitriding in a partly dissociated ammonia at temperatures between 410 and 570 °C. Hydrogen chloride admixture to active atmosphere was used as a surface activator. Structure of the nitrided layers were examined using scanning and transmission electron microscopy, X-ray microanalysis (EDX and WDX), and X-ray diffraction. The influence of the initial steel heat treatment on the nitriding kinetics has been considered. 17-4 PH stainless steel was nitrided at various heat treatment conditions, i.e. after solution treatment or ageing at different temperatures. The influence of precipitation processes taking place during the heat treatment before nitriding on the diffusive process kinetics was proven. It was found that, that increasing of steel ageing temperature up to 600 °C before nitriding effects on an increasing of the nitriding kinetics. 相似文献
18.
The effect of different surface treatments on the wear resistance of Ti-6Al-4V alloy has been investigated. For this purpose, plasma nitriding treatment was performed in a gas mixture 75% N2-25% Ar, for 1 h treatment time and at 750 °C. The thin films were deposited using CFUMBS technique. The results showed that more surface roughness was obtained for nitrided specimens compared with thin film deposited specimens. It was also observed that both surface treatments improved the wear resistance of Ti-6Al-4V alloy. It was determined that plasma nitrided specimens exhibited excellent wear resistance compared with thin film deposited ones when applied load increased. Similar results were obtained from surface hardness measurements, and it was observed that load bearing capacity increased after plasma nitriding. The corrosion resistance of both surface treatments showed similar properties. 相似文献
19.
Effect of heat treatments (namely T6, T73, RRA, OP1 and OP2) on the tensile strength (TS) and stress corrosion cracking (SCC) resistance of aluminum alloy 7050 in 3.5% NaCl solution at pH 12 has been investigated using constant extension rate tester (CERT). T6 increases the TS but decreases the SCC-resistance. To the opposite, T73 (i.e., T6 + 160 °C/30 h) increases the SCC-resistance but decreases the TS. Retrogression and re-aging (RRA, i.e., T6 + 200 °C/10 min + water quench + 120 °C/24 h) increases both TS and SCC-resistance but this treatment confines only to thin and small specimens. Step-quench aging (SQA, i.e., 470 °C/1 h + step-quench to 200 °C/1 min + water quench/or air cooling + natural aging at room temperature/1 week + 120 °C/24 h) provides a relatively practical treatment to enhance both the TS and SCC-resistance even the specimen either having quenched in water (OP1) or cooled in the air (OP2) in the process. Through electrochemical testing and micro-structural examination, we found that both the TS and SCC-resistance of AA7050 is governed by the microstructures that depend on heat treatments. 相似文献
20.
1. | The gasdynamic and energetic parameters of discharge in ion nitriding of steel were optimized. |
2. | The structure and phase composition of the diffusion layer can be controlled by changing the pressure and the composition of the saturating atmosphere. |
3. | In ammonia plasma the depth of the diffusion layer is largest on commercial iron and steels 40Kh and 38KhMYuA at a pressure of 2 mm Hg at temperatures of 520–570° and at 6 mm Hg at 650°. |
4. | The addition of argon to ammonia plasma makes it possible to obtain a nitrided layer on a base of high-nitrogen solid solution. Nitriding in mixtures with 5–15% NH3 and 95–85 vol. % Ar at pressures of 0.3–0.6 mm Hg provide a depth 50% larger than nitriding in ammonia plasma. |
5. | Nitriding in a mixture of ammonia and carbon-containing gas increases the depth of the nitride zone. With 40 vol. % or more propane in the mixture the interaction of the plasma with the surface of the part ceases. The optimal concentration of propane in the mixture with ammonia is 8–12 vol. %. |