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脉冲工艺参数对气体氮碳共渗层深度的影响 总被引:2,自引:0,他引:2
采用氨气加少量CO2进行脉冲气体氮碳共渗,探讨在固定温度、时间下脉冲幅度、保压时间对氮碳共渗渗层的影响。结果表明,在共渗温度、时间一定的情况下,随着保压时间的延长,化合物层(白亮层)逐渐减少;随着脉冲幅度的不断增加,化合物层先增加后减少,且保压时间的变化比脉冲幅度的变化对氮碳共渗化合物层影响更大。因此通过调整脉冲工艺参数有效控制化合物层的厚度,可以满足不同材料的技术要求。 相似文献
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Gayoung Park Gyuyeol Bae Kyungil Moon Changhee Lee 《Journal of Thermal Spray Technology》2013,22(8):1366-1373
In this work, the effects of plasma nitriding (PN) and nitrocarburizing on HVOF-sprayed stainless steel nitride layers were investigated. 316 (austenitic), 17-4PH (precipitation hardening), and 410 (martensitic) stainless steels were plasma-nitrided and nitrocarburized using a N2 + H2 gas mixture and the gas mixture containing C2H2, respectively, at 550 °C. The results showed that the PN and nitrocarburizing produced a relatively thick nitrided layer consisting of a compound layer and an adjacent nitrogen diffusion layer depending on the crystal structures of the HVOF-sprayed stainless steel coatings. Also, the diffusion depth of nitrogen increased when a small amount of C2H2 (plasma nitrocarburizing process) was added. The PN and nitrocarburizing resulted in not only an increase of the surface hardness, but also improvement of the load bearing capacity of the HVOF-sprayed stainless steel coatings because of the formation of CrN, Fe3N, and Fe4N phases. Also, the plasma-nitrocarburized HVOF-sprayed 410 stainless steel had a superior surface microhardness and load bearing capacity due to the formation of Cr23C6 on the surface. 相似文献
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R.L. Liu 《Surface & coatings technology》2010,204(14):2251-123
17-4PH martensitic precipitation hardening stainless steel was plasma nitrocarburized at 430 °C and 460 °C for 8 h. The nitrocarburized layers were characterized by optical microscope, scanning electron microscope, X-ray diffractometer, microhardness tests, pin-on-disc tribometer and the anodic polarization method in a 3.5% NaCl solution. The results show that the microstructure of plasma nitrocarburized layer is characterized by a compound layer with no evident diffusion zone. The phases in the 430 °C treated layer are mainly of γ′-Fe4N, nitrogen and carbon expanded martensite (α′N), and some incipient CrN phases. When the temperature increases up to 460 °C, there is no evidence of α′N phase. The processes of bulk precipitation hardening and surface treatment by plasma nitrocarburizing can be successfully combined in a single-step process on this steel. The hardness of modified layer can reach up to 1186HV, which is 3 times higher than that of untreated steel. The wear and corrosion resistance of the specimens can be apparently improved by plasma nitrocarburizing. The 460 °C/8 h treated specimen has the best wear and corrosion resistance in the present test conditions. 相似文献
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LEE Insup 《稀有金属(英文版)》2006,25(Z2)
Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of AISI 4140 steel.Plasma nitrocarburizing was conducted for 3 h at 570 ℃ in the nitrogen, hydrogen and methane atmosphere to produce the ε-Fe2-3(N,C) phase.It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of ε-phase, with a small proportion of γ'-Fe4(N,C) phase.The thickness of the compound layer was about 10 μm and the diffusion layer was about 300 μm in thickness, respectively.Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at a constant temperature of 500 ℃ for 1 h.The very thin magnetite (Fe3O4) layer 1-2 μm in thickness on top of the compound layer was obtained by plasma post oxidation.It was confirmed that the corrosion characteristics of the nitrocarburized compound layer can be further improved by the application of the superficial magnetite layer. 相似文献
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38CrMoAlA、40Cr钢经不同渗氮工艺处理后的性能研究 总被引:3,自引:2,他引:3
研究了38CrMoAlA和40Cr钢经气体渗氮、气体氮碳共渗、离子渗氮处理后渗氮层的组织、硬度、摩擦磨损和腐蚀性能。试验结果表明,38CrMoAlA钢渗氮层的硬度及在3.5%NaCl溶液中的耐蚀性能高于40Cr钢,但抗摩擦磨损性能不如40Cr钢。依气体渗氮、气体氮碳共渗到离子渗氮的顺序,渗氮层的抗磨损性能逐次提高,但抗腐蚀能力逐次降低。从钢的化学成分、渗氮层的硬度和韧性出发,对38CrMoAlA和40Cr钢渗氮层的性能差异进行了分析与总结。 相似文献
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Plasma nitrocarburizing treatments of AISI 4140 low alloy steel have been carried out in a gas mixture of 85% N2-12% H2-3% CO2. All treatments were performed for 5 h at a chamber pressure of 4 mbar. Different treatment temperatures varying from 520
to 620 °C have been used to investigate the effect of treatment temperature on the corrosion and hardness properties and also
microstructure of the plasma nitrocarburized steel. Scanning electron and optical microscopy, x-ray diffraction, microhardness
measurement, and potentiodynamic polarization technique in 3.5% NaCl solution were used to study the treated surfaces. The
results revealed that plasma nitrocarburizing at temperatures below 570 °C can readily produce a monophase ε compound layer.
The compound layer formed at 620 °C is composed of two sub-layers and is supported by an austenite zone followed by the diffusion
layer. The thickest diffusion layer was related to the sample treated at 620 °C. Microhardness results showed a reduction
of surface hardness with increasing the treatment temperature from 520 to 620 °C. It has also been found that with increasing
treatment temperature from 520 to 545 °C the corrosion resistance increases up to a maximum and then decreases with further
increasing treatment temperature from 545 to 620 °C. 相似文献
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Insup Lee 《Metals and Materials International》2008,14(1):77-81
Plasma nitrocarburizing and post-oxidation treatments were performed to improve the wear and corrosion resistance of S45C
steel. Plasma nitrocarburizing was conducted for 3 h at 570°C in a nitrogen, hydrogen and methane atmosphere to produce the
ε-Fe2−3(N,C) phase. It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of the ∈-phase
with traces of the γ′-Fe4(N,C) phase. The thickness of the compound layer was approximately 12 μm and the diffusion layer was approximately 300 μm
in thickness. Plasma post oxidation was performed on nitrocarburized samples with various oxygen/hydrogen ratios at a constant
temperature of 500°C for 1 h. The very thin magnetite (Fe3O4) layer 1 μm to 2 μm in thickness on top of the compound layer was obtained by plasma post oxidation. It was also confirmed
that further improvement of the corrosion characteristics of the nitrocarburized compound layer was possible with an application
of the superficial magnetite layer. Finally, throttle valve shafts of S45C steel were treated under optimum plasma processing
conditions. Accelerated life time test results using a throttle body assembled with a shaft treated by plasma nitrocarburising
and post oxidation showed that plasma nitrocarburizing and plasma post-oxidation processes could be a viable technology in
the very near future in place of Cr6 plating. 相似文献
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E. Roliński A. Konieczny G. Sharp 《Journal of Materials Engineering and Performance》2009,18(8):1052-1059
Two cast irons, pearlitic-ferritic gray and ferritic ductile, were plasma and gas nitrocarburized at the same temperature
and for the same processing time to produce a compound zone of about 10-14 μm thick. It was demonstrated that both processes
caused changes in the surface roughness of the irons, and the most dramatic increase of roughness was observed after gas nitrocarburizing
of the gray cast iron. It was shown that the primary reason that the results were not the same is the difference in the nitriding
mechanism. Significant penetration of the surface voids and imperfections between the graphite particles and the metallic
matrix by ammonia molecules led to the formation of a locally thicker compound zone and a bulging of the metallic matrix above
the surface. This phenomenon did not occur in the plasma process and as a result the surface changes were much smaller than
in the gas process. 相似文献
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Corrosion behaviour of nitrocarburized steels Diffusion coatings have been used increasingly to modify surface properties of various machine components for several applications. In general, these coatings are used to improve the wear behaviour. Frequently, it is desirable that the corrosion behaviour will be improved at the same time. In this investigation, the corrosion behaviour of various diffusion coating-substrate-combinations has been studied. The coatings developed by three different nitrocarburizing processes, namely saltbath, gas and plasma nitrocarburizing, were conducted on five various steel substrates. These substrates were St 52-3, Ck 45, 42 CrMo 4, 30 CrNiMo 8 and × 20 Cr 13. The thickness of the compound layers and their porosity were measured using optical microscopy. The structure of the compound layers was characterized using an X-ray diffractometer and their surface roughness by a stylus profilometer. The corrosion test was carried out using a salt-water spray test. The predominant corrosion mechanisms have been evaluated using scanning electron microscopy. It was found that the employed nitrocarburizing processes have improved the corrosion resistance of all tested coating-substrate-combinations comparing with that of the base materials. In general, the corrosion resistance increases with an increase of the compound layer's thickness and after an oxidation process. The best coating-substrate-combinations to improve the corrosion behaviour were salt-bath nitrocarburized tempering steels, whereas the thin layers of the plasma nitrocarburized specimens were the worst. 相似文献
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The Influence of Method of Carburizing and Nitrocarburizing on the Microstructure and Properties of Tool Steels 总被引:1,自引:0,他引:1
TomaszBabul NataliaKucharieva AleksanderNakonieczny JanSenatorski 《材料热处理学报》2004,25(5):386-389
The paper presents the results of wear and metallography tests of tool steel grades: ASTM A681, ChI2M and Ch12FS per GOST, AMS 6437E i BS X46Cr13, all surface hardened by the Carbo process (carburizing) and by the NiCar process (nitrocarburizing). The therrno-chemical treatment was conducted in powder pack for a duration of 6 h (carburizing) and for 4 h in the case of nitrocarburizing. Factors investigated were: morphology, depth and microhardness of the cases obtained, their microstructure, as well as phase composition. Wear tests were conducted by the three cylinder-cone method.Wear velocity was 0.58 m/s, unit load was 50 MPa and 400Mpa, wear path was 3470 m. Oil SAE30 was applied at the rate of 30 drops per minute. 相似文献
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P. Bala Srinivasan C. V. Krishnakumar N. Krishnaraj 《Journal of Materials Engineering and Performance》2002,11(5):509-515
Salt bath nitrocarburizing is a well-known thermochemical diffusion process for enhancing the tribological and corrosion properties
of ferrous components. The current work describes the role of a compound layer developed during nitrocarburizing, both in
the ferritic and austenitic regimes of Fe-N-C system, on the sliding wear behavior of a medium carbon steel. The wear behavior
of the nitrocarburized steel discs was assessed by the pin-on-disc tests (ASTM G 99-99) under different normal loads running
against a hardened SAE52100 pin. It was observed that the compound layer on the surface not only controlled the wear rate
but also resisted the adhesive wear/transfer of material from pin to disc, aside from providing low-friction coefficients. 相似文献