The main objective of the die heat treatment is to enhance the surface hardness and wear properties to extend the die service life. In this paper, a series of heat treatment experiments were conducted under different ...The main objective of the die heat treatment is to enhance the surface hardness and wear properties to extend the die service life. In this paper, a series of heat treatment experiments were conducted under different atmospheric conditions and length of treatment. Four austenitization atmospheric conditions were studied and although each heat treatment condition resulted in a different hardness profile, it did not affect the results for gas nitriding. All samples subjected to the nitriding process produced similar thicknesses of hardened case layer with average hardness of 70 - 72 HRC if the initial carbon content is not too low. It was shown that heat treatment without atmospheric control results in a lower hardness on the surface since the material was subjected to decarburization effect. The stainless steel foil wrapping around the sample and heat treatment in a vacuum furnace could restrict the decarburization process, while pack carburization heat treatment resulted in a carburization effect on the material.展开更多
The present work is to characterize both processes of thermochemical treatments: plasma nitriding and gas. The tests were carried out in collaboration with the Franco-Tunisian heat treatment (F3T) applied to a widely ...The present work is to characterize both processes of thermochemical treatments: plasma nitriding and gas. The tests were carried out in collaboration with the Franco-Tunisian heat treatment (F3T) applied to a widely used steel in industrial production as a tool for hot work on X38CrMoV5 (AISI H13). The material underwent a first cycle of hardening heat treatment at 1030℃ followed by two successive incomes at 550℃ and 590℃. After nitriding (ion and gas), the quantification of wear was performed in the laboratory of tribology at SUPMECA (St. Ouen). After defining the test conditions on the alternative tribometer ensuring on one hand a quantitatively sufficient wear and avoiding on the other hand, the phenomenon of jamming. The conditions chosen are: 58.8 N load, frequency 0.5 Hz, friction coefficient μ = 0.5. The wear tracks were scanned using the profilometer Talysurf 5 M type, which allowed us to assess the volume used and the wear rate. Moreover, these tracks were characterized by metallography. What emerges from this work is that the control parameters of ion nitriding ensures a better depth of treatment for the same holding time with a total absence of the white layer known for chipping and fragility.展开更多
Ni-P-SiC_(P) coatings were deposited on 42CrMo steel by electroless plating.The surface morphologies and phase structures of the Ni-P-SiC_(P) coatings processed under different SiC_(P) concentrations at different heat...Ni-P-SiC_(P) coatings were deposited on 42CrMo steel by electroless plating.The surface morphologies and phase structures of the Ni-P-SiC_(P) coatings processed under different SiC_(P) concentrations at different heat treatment temperatures were analyzed.The microhardness,corrosion resistance,and wear resistance of the Ni-P-SiC_(P) coatings were studied.Results show that Ni-P-SiC_(P) coatings exhibit cauliflower-like morphology.Increasing the SiC_(P) concentration can reduce the size of cellular structure.The microhardness and corrosion resistance are initially increased and then decreased with the increase in SiC_(P) concentration.The maximum microhardness and corrosion potential are 7379 MPa and−0.363 V,respectively,when the SiC_(P) concentration is 5 g/L.The Ni-P-SiC_(P) coatings exhibit an amorphous structure,and the width of the diffuse diffraction peak becomes narrower with the increase in SiC_(P) concentration.It is suggested that SiC_(P) inhibits the deposition of P and promotes the microcrystalline transformation.After heat treatment at 350℃,the Ni-P-SiC_(P) coatings are crystallized,resulting in the precipitation of Ni3P phase.Heat treatment at 400℃ for 1 h maximizes the structure.The synergistic effect of the Ni3P precipitate phase and SiC_(P) dispersion phase promotes the densification of the cellular structure,leading to the optimal microhardness(13828 MPa),optimal corrosion resistance(−0.277 V),and excellent wear resistance.The wear mechanism is dominated by micro-cutting abrasive wear with slight adhesive and oxidative wear.展开更多
In order to research the effect of microalloying Nb,the microstructure and heat treatment distortion of case carburizing steels with and without Nb addition are compared.Results show that a uniform and fine prior aust...In order to research the effect of microalloying Nb,the microstructure and heat treatment distortion of case carburizing steels with and without Nb addition are compared.Results show that a uniform and fine prior austenite grain size was obtained for the steel with the addition of 0.03 wt.%Nb even after being carburized at 980℃for 37 h,resulting in a very deep hardened layer of about 4 mm.Nb is an effective microalloying element to hinder austenite grain growth of gears during high-temperature carburizing.Theoretical calculation and experimental observation of NbC precipitates indicate that fine NbC precipitates have not evidently dissolved at 980℃,and thus they can act as grain refiners due to pinning effect.Heat treatment distortion of Nb-added steel is much lower than that of the steel without Nb addition.It may be contributed to its fine and uniform grain size,which presumably influences stress during martensitic transformation.展开更多
The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced th...The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced the retained austenite and increased the carbide amount.In addition,after the cryogenic heat treatment,carbide shows a more uniform distribution,as compared to the conventionally treated ones.It was also clarified that the hardness of the cryogenically treated samples was improved,but the relative improvement decreases with the distance as the surface increases.It has been shown that the wear resistance improves due to the cryogenic heat treatment,and the predominant wear mechanism is a combination of the adhesive and tribo-chemical wear.展开更多
文摘The main objective of the die heat treatment is to enhance the surface hardness and wear properties to extend the die service life. In this paper, a series of heat treatment experiments were conducted under different atmospheric conditions and length of treatment. Four austenitization atmospheric conditions were studied and although each heat treatment condition resulted in a different hardness profile, it did not affect the results for gas nitriding. All samples subjected to the nitriding process produced similar thicknesses of hardened case layer with average hardness of 70 - 72 HRC if the initial carbon content is not too low. It was shown that heat treatment without atmospheric control results in a lower hardness on the surface since the material was subjected to decarburization effect. The stainless steel foil wrapping around the sample and heat treatment in a vacuum furnace could restrict the decarburization process, while pack carburization heat treatment resulted in a carburization effect on the material.
文摘The present work is to characterize both processes of thermochemical treatments: plasma nitriding and gas. The tests were carried out in collaboration with the Franco-Tunisian heat treatment (F3T) applied to a widely used steel in industrial production as a tool for hot work on X38CrMoV5 (AISI H13). The material underwent a first cycle of hardening heat treatment at 1030℃ followed by two successive incomes at 550℃ and 590℃. After nitriding (ion and gas), the quantification of wear was performed in the laboratory of tribology at SUPMECA (St. Ouen). After defining the test conditions on the alternative tribometer ensuring on one hand a quantitatively sufficient wear and avoiding on the other hand, the phenomenon of jamming. The conditions chosen are: 58.8 N load, frequency 0.5 Hz, friction coefficient μ = 0.5. The wear tracks were scanned using the profilometer Talysurf 5 M type, which allowed us to assess the volume used and the wear rate. Moreover, these tracks were characterized by metallography. What emerges from this work is that the control parameters of ion nitriding ensures a better depth of treatment for the same holding time with a total absence of the white layer known for chipping and fragility.
基金Science Research Project of Handan Bureau of Science and Technology(21422075242)。
文摘Ni-P-SiC_(P) coatings were deposited on 42CrMo steel by electroless plating.The surface morphologies and phase structures of the Ni-P-SiC_(P) coatings processed under different SiC_(P) concentrations at different heat treatment temperatures were analyzed.The microhardness,corrosion resistance,and wear resistance of the Ni-P-SiC_(P) coatings were studied.Results show that Ni-P-SiC_(P) coatings exhibit cauliflower-like morphology.Increasing the SiC_(P) concentration can reduce the size of cellular structure.The microhardness and corrosion resistance are initially increased and then decreased with the increase in SiC_(P) concentration.The maximum microhardness and corrosion potential are 7379 MPa and−0.363 V,respectively,when the SiC_(P) concentration is 5 g/L.The Ni-P-SiC_(P) coatings exhibit an amorphous structure,and the width of the diffuse diffraction peak becomes narrower with the increase in SiC_(P) concentration.It is suggested that SiC_(P) inhibits the deposition of P and promotes the microcrystalline transformation.After heat treatment at 350℃,the Ni-P-SiC_(P) coatings are crystallized,resulting in the precipitation of Ni3P phase.Heat treatment at 400℃ for 1 h maximizes the structure.The synergistic effect of the Ni3P precipitate phase and SiC_(P) dispersion phase promotes the densification of the cellular structure,leading to the optimal microhardness(13828 MPa),optimal corrosion resistance(−0.277 V),and excellent wear resistance.The wear mechanism is dominated by micro-cutting abrasive wear with slight adhesive and oxidative wear.
基金the Ministry of Science and Technology(MOST)of China under the contract of No.2016YFB0300102The financial support from CITIC Metals is also acknowledged.
文摘In order to research the effect of microalloying Nb,the microstructure and heat treatment distortion of case carburizing steels with and without Nb addition are compared.Results show that a uniform and fine prior austenite grain size was obtained for the steel with the addition of 0.03 wt.%Nb even after being carburized at 980℃for 37 h,resulting in a very deep hardened layer of about 4 mm.Nb is an effective microalloying element to hinder austenite grain growth of gears during high-temperature carburizing.Theoretical calculation and experimental observation of NbC precipitates indicate that fine NbC precipitates have not evidently dissolved at 980℃,and thus they can act as grain refiners due to pinning effect.Heat treatment distortion of Nb-added steel is much lower than that of the steel without Nb addition.It may be contributed to its fine and uniform grain size,which presumably influences stress during martensitic transformation.
基金the Majlesi Branch,Islamic Azad University for the support of this work
文摘The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced the retained austenite and increased the carbide amount.In addition,after the cryogenic heat treatment,carbide shows a more uniform distribution,as compared to the conventionally treated ones.It was also clarified that the hardness of the cryogenically treated samples was improved,but the relative improvement decreases with the distance as the surface increases.It has been shown that the wear resistance improves due to the cryogenic heat treatment,and the predominant wear mechanism is a combination of the adhesive and tribo-chemical wear.
