Papers by Keyword: Nitrocarburizing

Abstract: In this work we show our result of in-situ nitrocarburizing and nitriding treatments AISI316L specimens. Part of the samples have been depassivated ex-situ and coated with a Ni layer, while other specimens received in-situ depassivation. Processing was carried out in a custom built reaction chamber attached to a Bruker D8 Advance diffractometer. We monitored the 111 peak of both the base material and expanded austenite. From the shrinkage of the base material peak the total thickness of the expanded austenite can be determined. Applying both N and C resulted in a more than 10 times faster growth of the expanded austenite than with N only. The growth is thermally activated. The activation energy for nitrocarburizing is 164 kJ/mol. This is in agreement with the activation energy of the diffusion of interstitials. Detailed analysis of the expanded austenite peak allowed the derivation of a “master curve” for the composition depth profile. This suggest that two interacting process controls the evolution. The width of the reaction zone is limited by the diffusion at low concentration side. The total concentration is determined by the reaction at the interface.

Abstract: Gas nitrocarburizing combined with a post-oxidation treatment is an interesting industrial process developed in order to improve wear and corrosion resistance of low alloyed steel components. In the present work, the microstructure resulting by a thermochemical treatment, which comprises nitriding, nitrocarburizing and post-oxidation stages, applied to an industrial 16MnCr5 component, has been studied. Both the nitriding and nitrocarburizing temperatures were systematically changed in order to study the resulting phases in the compound layer. The depth of the compound layer have been measured by optical microscopy to evaluate the effect due to the variations in the process variables during the nitrocarburizing process. Moreover, the microstructure has been investigated by means of a scanning electron microscope equipped with a electron backscatter diffraction detector in order to assess the amount and the distribution of Fe-N-C phases. A temperature increase from 510 up to 550°C during the nitriding process inside a NH₃ atmosphere induces a higher fraction of ε-Fe_2-3(C,N) compounds. On the contrary, nitrocarburizing at 600°C instead of 580°C under a gaseous mix of NH₃ (50%), CO₂ and N₂ favors a greater amount of γ'-Fe₄(C,N) nitrides. A greater amount of porosity in the outer part of the compound layer favors a thicker oxide film obtainable with the post-oxidation process.

Abstract: Nitrocarburized steel surfaces are often used in tribological forming applications due to their beneficial sliding properties. One typical application field can be found in bending machines where the nitrocarburized layer can withstand massive volume loss and prevent from adhesion of the work sheet material. However, under non-lubricated sliding conditions abrupt failure of the nitrocarburized layer can occur, which results in pronounced increase of friction and wear. In order to characterise the wear mechanisms of nitrocarburized surfaces under non-lubricated sliding conditions, a lab-scale study was carried out. Different nitrocarburizing processes including plasma, gas and salt bath nitrocarburizing were investigated. Oscillating sliding tests with DIN 100Cr6 bearing steel cylinder sliding against nitrocarburized plate were performed at contact pressures typical for bending machines. Evaluation of wear was performed by white-light interferometer with measurements of the wear-scar topography and a subsequent calculation of the average wear depth. A strong influence of the nitrocarburizing process on friction and wear behaviour was observed. This behaviour could be correlated with the microstructure of the compound layer.

Abstract: Surface hardening on local bolt (C = 0.071%) with Radio Frequency (RF) - plasma nitrocarburizing apparatus has been carried out. Some local bolt component was cleaned with distilled water. The type of material of local bolt component was low carbon steel, carbon concentration 0.071%. After that the local bolt component was cleaned with acetone. The natural oxide layer on the surface of the local bolt material was etched with HF for 1 until 3 minutes. The local bolt component was cleaned again with distillation water. Then the local bolt component was sprayed with nitrogen gas. After that the local bolt component was hardened on the material surface with RF plasma nitrocarburizing at a temperature of 400 °C, for holding time 7 hours. Sample number 1 was sample before nitrocarburization. Sample number 2 was sample after nitrocarburization at a temperature of 400 °C, for 7 hours. Then the local bolt component was cut with mower as samples for microstructure observed. The samples were mounted, polished, and etched for microstructure observation with optical microscope. The surface hardness of the samples was tested with O.M.A.G micro-hardness Vickers, MHX 10, apparatus. The expenses tracking was 300 grf, and the times tracking was 15 seconds. The results show that the hardness of sample of bolt before nitrocarburization was 154.5 Kgf/mm², after the sample was nitrocarburized at a temperature of 400 °C for 7 hours, the maximum hardness on the surface increased up to 205.6 Kgf/mm². Matrixes on the base material were austenite, ferrite, and perlite.

Abstract: A study of surface hardening on local bolts (C=0.01%) at a temperature of 400°C for 5 and 6 hours with nitrocarburizing using RF-plasma apparatus. The objective of this experiment was to seek a surface material of local bolts that is more resistant to friction and having better surface uniformity, higher hardness and higher corrosion resistance. The experiment was conducted on the local bolts (C = 0.01%) with a radio-frequency (RF) plasma nitrocarburizing equipment. The nitrocarburization was done on the local bolts at a temperature of 400°C, with a variation of nitrocarburizing times of 5 and 6 hours. The results showed that the average hardness of local bolt samples before nitrocarburization was 136.08 kgf/mm². After nitrocarburization at a temperature of 400°C for 5 hours, the average hardness of local bolt samples was 199.1 kgf/mm². After nitrocarburization at a temperature of 400°C for 6 hours, the average hardness of local bolt samples was 201.12 kgf/mm². The matrixes on the base material were ferrite, austenite, and pearlite.

Abstract: Surface hardening on local disc brakes with DC-plasma nitrocarburizing apparatus has been carried out. Local disc brake was nitrocarburized at temperatures of 700 °C, 800°C, and 900°C for 3 hours, respectively. The results show that the hardness of sample of local disc brake before nitrocarburization was 167.86 Kgf/mm², after the sample was nitrocarburized at temperature 900 °C for 3 hours, the hardness increased up to 649.38 Kgf/mm². Matrixes on the base material were austenite, ferrite, and perlite.

Abstract: Review of results in anodic plasma electrolytic saturation of structural steels with nitrogen and carbon in the aqueous electrolytes containing ammonia chloride and required additional constituents is presented. Proposed nitrohardening technology of the medium-carbon steels includes the short-time nitrogen saturation with the following hardening in the electrolyte. Short-time anodic carburizing possibility of the low-carbon steels with following hardening is shown. Treatment samples microhardness is 630±30 HV, their surface roughness decreases from 1.2 to 0.22 μm.

Abstract: Alternating surface oxide and hardened layers were fabricated by means of anodic plasma nitrocarburizing of low-carbon steel in aqueous ammonium chloride/carbamide solutions. The effect of electrolyte composition and treatment conditions on the phase characteristics, structure and properties of the surface layers was studied. The distributions of hardness, phase and structure composition of the surface layers were defined. Controllability of diffusion saturation with nitrogen and carbon by variation of electrolyte composition and treatment temperature was shown. The formation of nitrogen and carbon, which are diffusing into the steel surface at anodic plasma electrolytic nitrocarburizing was described.

Abstract: The paper presents a research about influence of nitrocarburizing on wear resistance of metal coating layer. The research was made using six types of electrodes (El CrMn2, ElCrW8Co, El CrW2, E Cr25Ni20R, E 3161, El 62 H) for metal coating. After metal coating, were applied three variants of plasma nitrocarburizing, and was study their influence on wear resistance. Evaluation of results was made by weighing loss of samples after wearing.

Abstract: Analyzes the reason why renitrocarburized element could not get desired surface quality as the first. Improve the craft. Conduct trial and testing. The surface hardness and compounds layer depth of the Renitrocarburized element can back to the same level as the first time. Furthermore, the infiltration layer microstructure is consistent with that in the first nitro carburizing.