The Experts below are selected from a list of 8337 Experts worldwide ranked by ideXlab platform
Sahand Behrangi - One of the best experts on this subject based on the ideXlab platform.
-
Plasma Nitriding of Steels
Topics in Mining Metallurgy and Materials Engineering, 2017Co-Authors: Hossein Aghajani, Sahand BehrangiAbstract:This book focuses on the effect of Plasma Nitriding on the properties of steels. Parameters of different grades of steels are considered, such as structural and constructional steels, stainless steels and tools steels. The reader will find within the text an introduction to Nitriding treatment, the basis of Plasma and its roll in Nitriding. The authors also address the advantages and disadvantages of Plasma Nitriding in comparison with other Nitriding methods.
-
Conventional DC Plasma Nitriding
Plasma Nitriding of Steels, 2016Co-Authors: Hossein Aghajani, Sahand BehrangiAbstract:As known before, the usual source for generating the Plasma in Plasma Nitriding system is DC current (conventional or pulsed). This chapter just includes the results obtained by conventional DC Plasma Nitriding system on different grades of steels including stainless steels (austenitic, martensitic or precipitation hardening types), tool steels, and structural and constructional steels. This chapter consists of microstructural, mechanical, and corrosion properties obtained after conventional DC Plasma Nitriding of steels.
-
Active Screen Plasma Nitriding
Plasma Nitriding of Steels, 2016Co-Authors: Hossein Aghajani, Sahand BehrangiAbstract:Conventional Plasma Nitriding has some limitations and disadvantages such as edge effect, hollow-cathode effect (The hollow-cathode effect usually seen in industry resulted by incorrect fixturing. This problem arises from insufficient distance between the parts to be nitrided. In this case, the glow discharge of near specimens are overlapped in cavities leads to the cascading of current densities and severe overheating of the parts.), distortion, and overheating of the specimen. Because of the above-mentioned problems, some new methods were presented to avoid the direct formation of Plasma on the surface and consequent problems. One of the methods is active screen or cathodic cage Plasma Nitriding.
-
Pulsed DC Glow Discharge Plasma Nitriding
Plasma Nitriding of Steels, 2016Co-Authors: Hossein Aghajani, Sahand BehrangiAbstract:Pulsed power supply is used for Plasma Nitriding to overcome the problems of conventional DC Plasma Nitriding. Therefore, using this power source has provided some noticeable advantages such as the following: 1. A more accurate control on Nitriding process 2. Controlling and lowering the process temperature simply by adjusting the pulse width without any change in bias voltage 3. Avoiding the arcing phenomenon on the surface of the workpiece 4. A more uniform temperature distribution and lowering the overheating risk of the surface of the workpiece
-
Radiofrequency (RF) Plasma Nitriding
Plasma Nitriding of Steels, 2016Co-Authors: Hossein Aghajani, Sahand BehrangiAbstract:The usual Plasma Nitriding is done using glow discharge with the workpiece as cathode at pressures between 100 and 1000 Pa. This procedure leads to bombardment of the surface by energetic ions, therefore the temperature is high.
Jing Hu - One of the best experts on this subject based on the ideXlab platform.
-
An enhanced rapid Plasma Nitriding by laser shock peening
Materials Letters, 2018Co-Authors: Lei Tang, Jing HuAbstract:Abstract Laser shock peening was primarily adopted as a pretreatment prior to Plasma Nitriding for 42CrMo steel. It was found that laser shock peening had obvious enhancement effect on Plasma Nitriding. The thickness of compound layer and effective hardening layer could be effectively improved under the same Plasma Nitriding condition, which was about twice thicker as that of conventional Plasma Nitriding. Meanwhile, laser shock peening could significantly increase the surface hardness and slow down the decreasing trend of cross-sectional hardness. The significant enhancement effect of laser shock peening on Plasma Nitriding was mainly attributed to the increase of surface roughness from 0.015 μm to 0.454 μm and the pronounced defects in the deformation layer with a thickness of about 200 μm, the former was beneficial to the adsorption of nitrogen atoms, and the latter could promote nitrogen atoms diffusing inwards, thus increasing the microhardness in the Nitriding layer due to higher nitrogen concentration.
-
performance enhancement by Plasma Nitriding at low gas pressure for 304 austenitic stainless steel
Vacuum, 2017Co-Authors: Shijing Lu, Jingcai Li, Xiaobing Zhao, Shukai Wang, Jing HuAbstract:Abstract Plasma Nitriding was conducted at low gas pressure and low temperature of 400 °C for 304 austenitic stainless steel. The combined performance of the treated specimens was evaluated by scanning electronic microscopy (SEM), X-ray diffractometer (XRD), microhardness tester, ball-on-disc tribometer and electrochemical polarization. The results showed that an expanded austenite (γ N ), also called S phase layer was formed after Plasma Nitriding at low gas pressure and low temperature of 400 °C, and the Nitriding efficiency was significantly improved at lower gas pressure; maximum expanded austenite layer of 51.7 μm and effective hardening layer of 72 μm were obtained at low gas pressure of 100 Pa. Surface hardness and wear resistance were enhanced dramatically by Plasma Nitriding at 100 Pa, and the weight loss after wear test decreased from 0.102 g to the minimum of 0.013 g. Meanwhile, the corrosion resistance was improved after Plasma Nitriding at 100 Pa, the minimum corrosion current of 0.009 μA ·cm −2 and the maximum corrosion potential of −361.9 mV are obtained.
-
Plasma Nitriding without formation of compound layer for 38CrMoAl hydraulic plunger
Vacuum, 2017Co-Authors: Yao Chen, Chenkai Zhang, Xuemei Ye, Zhixiu Wang, Xiaobing Zhao, Lei Song, Renguo Song, Jing HuAbstract:Abstract In this study, low temperature Plasma Nitriding (LPN) was primarily used in 38CrMoAl hydraulic plunger to overcome the peeling problem of the compound layer in real application. The cross-sectional microstructures of the treated samples were observed by optical metallography, phase constituents were determined by X-ray diffraction (XRD), the microhardness profile and brittleness of surface were measured by microhardness tester. The results showed that no compound layer was formed while Plasma Nitriding at 450 °Cfor 6 h, and XRD also confirmed that there existed no γ′-Fe 4 N. Meanwhile, the brittleness was decreased at lower temperature Plasma Nitriding comparing with normal Plasma Nitriding (NPN), due to no brittle compound layer formed on the outmost layer.
-
The effect of sand blasting pretreatment on Plasma Nitriding
Vacuum, 2017Co-Authors: Bin Miao, Yating Chai, Lu Song, Jing HuAbstract:Abstract In this study, sand blasting was conducted as a pretreatment prior to Plasma Nitriding, and the effect of sand blasting on Plasma Nitriding was evaluated by means of scanning electron microscopy (SEM), optical microscopy, X-ray diffraction (XRD), electrochemical polarization and pin-on-disk tribotester etc. The results showed that sand blasting could enhance the Nitriding efficiency and bring about much thicker nitrided layer than that of the nitrided-only sample under the same Plasma Nitriding condition, and the higher Nitriding efficiency could be ascribed to the higher surface free energy (SFE). Electrochemical measurements showed that the sand-blasted sample increased the corrosion potential by approximately 100 mV and a reduced the corrosion current by an order of magnitude in comparison with the nitrided-only sample. Meanwhile, the cross-sectional hardness and wear resistance were significantly improved, which could be attributed to the thicker compound layer with higher amount of e-Fe 2-3 N comparing with the nitrided-only sample.
-
a rapid d c Plasma Nitriding technology catalyzed by pre oxidation for aisi4140 steel
Materials Letters, 2014Co-Authors: Jingcai Li, Xingmei Yang, Shukai Wang, Jing HuAbstract:Abstract D.C. Plasma Nitriding (PN) of AISI4140 steel catalyzed by pre-oxidation was investigated primarily. The pre-oxidation was carried out in air prior to Plasma Nitriding. The results revealed that pre-oxidation had significant catalysis effect on Plasma Nitriding, the maximum compound layer thickness of 15 μm was obtained after Nitriding at 500 °C for 4 h under the optimum pre-oxidation (PO) condition of 300 °C and 30 min, which was two times thicker than that without pre-oxidation. The possible catalysis mechanism is due to the formation of a uniform nano-iron oxide particle along with some nanocracks and nanopores on the surface, which has the highest SFE.
C X Li - One of the best experts on this subject based on the ideXlab platform.
-
Active screen Plasma Nitriding of materials
International Heat Treatment & Surface Engineering, 2013Co-Authors: Thomas Bell, C X LiAbstract:AbstractThe rapid development and the uptake of Plasma Nitriding technology into industrial surface engineering have slowed down in recent years. This is attributed to some of the inherent shortcomings of conventional dc Plasma technology, for example, difficulties in maintaining a uniform chamber temperature, instability of the Plasma and potential surface damage to parts caused by arcing. Efforts in overcoming these problems have led to the development of active screen Plasma Nitriding (ASPN) technology. This review demonstrates that with all its technological and environmental advantages, ASPN can be used to treat low alloy steels, tool steels, stainless steels and other steels which can conventionally be nitrided with dc Plasma technology. In addition, ASPN can be used to treat non-conducting materials such as oxidised steels and polymeric materials which are not suitable for a dc Plasma Nitriding system. In the longer term, environmental friendly and technologically advanced Plasma Nitriding will out...
-
active screen Plasma Nitriding an overview
Surface Engineering, 2010Co-Authors: C X LiAbstract:AbstractExtensive researches carried out over the past few years have shown that the novel active screen Plasma Nitriding (ASPN) technique can be used to treat low alloy steels, stainless steels, tool steels and other steels to achieve identical Nitriding effects as the conventional DC Plasma Nitriding technology. Importantly, the ASPN technique provides the possibilities of treating non-electrical conducting materials such as steel with an oxidised surface and polymeric materials which are unattainable with a conventional DC Plasma system. Experimental results presented in this overview further demonstrate that sputtering and deposition play important roles in nitrogen mass transfer in ASPN. In order to achieve a desirable metallurgical response, materials for the active screen and the amount of bias applied to the component have to be considered in applications of active screen Plasma processing. The distance between the screen and the component surface also needs to be considered if the components to b...
-
Study on the active screen Plasma Nitriding and its Nitriding mechanism
Surface & Coatings Technology, 2006Co-Authors: C. Zhao, Hanshan Dong, C X Li, Thomas BellAbstract:Abstract The active screen Plasma and DC Plasma Nitriding of the low alloy steel 722M24 are investigated. Experimental results showed that the metallurgical characteristics and hardening effect on 722M24 steel nitrided by AS Plasma Nitriding at both floating potential and grounded potential were similar to those nitrided by DC Plasma Nitriding. Particles sputtered from the active screen and deposited on the specimen surface play the role of the nitrogen carrier in AS Plasma Nitriding. XRD and high-resolution SEM analysis indicated that the particles with sizes in sub-micron scale were Fe x N ( x > 2). Based on metallurgical analysis and Optical Emission Spectrometer (OES) experimental results, an AS Plasma Nitriding model has been proposed considering that AS Plasma Nitriding is a multi-stage process, involving sputtering, physical adsorption, desorption, diffusion and deposition.
-
Potential of Plasma Nitriding of polymer for improved hardness and wear resistance
Journal of Materials Processing Technology, 2005Co-Authors: C X Li, T BellAbstract:Abstract Samples of ultrahigh molecular weight polyethylene (UHMWPE) have been surface treated with the active screen (AS) Plasma Nitriding technique. The results show that AS Plasma Nitriding can improve the mechanical properties such as hardness, elastic modulus and creep resistance on the surface of the investigated polymer. As a result, the nitrided samples have improved wear resistance as compared to the untreated material. From a technological and economical point of view, active screen Plasma Nitriding (ASPN) is likely to have high potential for surface modification of polymers for improved surface hardness and wear resistance.
-
active screen Plasma Nitriding of austenitic stainless steel
Surface Engineering, 2002Co-Authors: C X Li, J Georges, Xiaoying LiAbstract:AbstractActive screen (AS) Plasma Nitriding is a new surface engineering technique which provides many advantages over conventional dc Plasma Nitriding. In this study the AS technique has been used to nitride austenitic stainless steel (AISI 316). The morphology, composition and properties of the AS Plasma nitrided layers have been characterised and compared with those of the normal dc Plasma nitrided layers. AS Nitriding can achieve similar hardening effects for austenitic stainless steel when compared to conventional dc Nitriding, and does not have the common problems associated with the dc technique such as ‘edging effect’. AS Nitriding at a lower temperature of 420° C can also produce a precipitation free layer, the S phase, on a 316 stainless steel surface. The AS nitrided S phase exhibits not only high hardness and wear resistance but also very good corrosion resistance.
Yuntao Xi - One of the best experts on this subject based on the ideXlab platform.
-
improvement of corrosion and wear resistances of aisi 420 martensitic stainless steel using Plasma Nitriding at low temperature
Surface & Coatings Technology, 2008Co-Authors: Yuntao XiAbstract:Abstract The influence of low temperature Plasma Nitriding on the wear and corrosion resistance of AISI 420 martensitic stainless steel was investigated. Plasma Nitriding experiments were carried out with DC-pulsed Plasma in 25% N2 + 75% H2 atmosphere at 350 °C, 450 °C and 550 °C for 15 h. The composition, microstructure and hardness of the nitrided samples were examined. The wear resistances of Plasma nitrided samples were determined with a ball-on-disc wear tester. The corrosion behaviors of Plasma nitrided AISI420 stainless steel were evaluated using anodic polarization tests and salt fog spray tests in the simulated industrial environment. The results show that Plasma Nitriding produces a relatively thick nitrided layer consisting of a compound layer and an adjacent nitrogen diffusion layer on the AISI 420 stainless steel surface. Plasma Nitriding not only increases the surface hardness but also improves the wear resistance of the martensitic stainless steel. Furthermore, the anti-wear property of the steel nitrided at 350 °C is much more excellent than that at 550 °C. In addition, the corrosion resistance of AISI420 martensitic stainless steel is considerably improved by 350 °C low temperature Plasma Nitriding. The improved corrosion resistance is considered to be related to the combined effect of the solid solution of Cr and the high chemical stable phases of ɛ-Fe3N and αN formed on the martensitic stainless steel surface during 350 °C low temperature Plasma Nitriding. However, Plasma Nitriding carried out at 450 °C or 550 °C reduces the corrosion resistance of samples, because of the formation of CrN and leading to the depletion of Cr in the solid solution phase of the nitrided layer.
-
improvement of mechanical properties of martensitic stainless steel by Plasma Nitriding at low temperature
Acta Metallurgica Sinica (english Letters), 2008Co-Authors: Yuntao XiAbstract:A series of experiments were carried out to study the influence of low temperature Plasma Nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma Nitriding experiments were carried out for 15 h at 350°C by means of DC-pulsed Plasma in 25%N2+75%H2 atmosphere. The microstructure, phase composition, and residual stresses profiles of the nitrided layers were determined by optical microscopy and X-ray diffraction. The microhardness profiles of the nitridied surfaces were also studied. The fatigue life, sliding wear, and erosion wear loss of the untreated specimens and Plasma Nitriding specimens were determined on the basis of a rotating bending fatigue tester, a ball-on-disc wear tester, and a solid particle erosion tester. The results show that the 350°C nitrided surface is dominated by ɛ-Fe3N and αN, which is supersaturated nitrogen solid solution. They have high hardness and chemical stabilities. So the low temperature Plasma Nitriding not only increases the surface hardness values but also improves the wear and erosion resistance. In addition, the fatigue limit of AISI 420 steel can also be improved by Plasma Nitriding at 350° C because Plasma Nitriding produces residual compressive stress inside the modified layer.
A Oztarhan - One of the best experts on this subject based on the ideXlab platform.
-
a comparative study of single and duplex treatment of martensitic aisi 420 stainless steel using Plasma Nitriding and Plasma Nitriding plus nitrogen ion implantation techniques
Surface & Coatings Technology, 2007Co-Authors: A Cetin, A Oztarhan, N ArtuncAbstract:Abstract Martensitic AISI 420 is a high chromium mold steel which is suitable for tools for molding corrosive plastics. In this study, micro-pulsed Plasma Nitriding and Plasma Nitriding + nitrogen ion implantation techniques have been used to improve the surface hardness and tribological properties of AISI 420 substrates. Firstly polished-AISI 420 samples are nitrided at 530 °C for 15 h at a pressure of 10 mbar. Then nitrided samples are implanted with nitrogen ions to a dose of 2 × 10 17 ions/cm 2 . Mechanical characterization of both of the modified and unmodified samples has been carried out by means of nano-hardness, wear resistance, friction coefficient and surface roughness measurements. It is found that the nano-hardness, wear resistance, friction coefficient and surface roughness values improve 1.6, 3.5, 1.4 and 10 times for Plasma nitrided samples, and 2.0, 4.6, 1.1 and 9 times for Plasma nitrided-plus-N + ion implanted samples, respectively, in comparison with unmodified AISI 420 samples. Both the Plasma Nitriding process and the Plasma Nitriding-plus-N + ion implantation treatment sample results are also compared. The improvement of the samples modified using Nitriding-plus-N + ion implantation process is found to be better than that of samples modified by the Nitriding process.
-
comparison of the mechanical properties of nitrogen ion implantation and micro pulsed Plasma Nitriding techniques of cr ni alloy
Surface & Coatings Technology, 2002Co-Authors: Mehmet Ali Gungor, Mehmet Sonugelen, Celal Artunc, A OztarhanAbstract:Abstract Cr–Ni alloys are frequently used in dentistry for economical reasons. While they gain popularity, an increase in systemic and local concerns of these dental metals is observed. With the progressions in surface technology, the surface characteristics of the metals can be changed. In this study, nitrogen ion (N ion) implantation and Plasma Nitriding techniques were used to change the properties of Cr–Ni alloy (Wirollay). Nitrogen implantation at dose 1×10 17 ion/cm 2 and micro-pulsed Plasma Nitriding techniques were applied to Cr–Ni alloy samples. After the process, the friction coefficient was decreased in ion implantation, but this ratio was increased in the Plasma Nitriding technique with respect to the substrate. The roughness did not change after N ion implantation but it increased after the Plasma Nitriding procedure. Wear volume of the implanted and Plasma Nitriding samples were lower than the substrate. Hardness values were increased four times for N ion implantation and eight times for the Plasma Nitriding technique.