Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely us...Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely used in fields such as injection molding,die casting,and stamping dies.Adding reinforcing particles into steel is an effective means to improve its performance.Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes,and their microstructures and properties were studied.The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined,which is particularly pronounced with fine Nb particles.In addition,element diffusion occurs between the particles and the matrix.The main phases of the base alloy are α-Fe and a small amount of γ-Fe.With the addition of Nb,part of the α-Fe is transformed into γ-Fe,and unmelted Nb phases appear.The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties.After aging treatment,the molten pools and grain boundaries become blurred,grains are further refined,and the interfaces around the particles are thinned.The aging treatment also promotes the formation of reverted austenite.The hardness,ultimate tensile strength,and volumetric wear rate of the base alloy reach 51.9 HRC,1704 MPa,and 17.8×10^(-6) mm^(3)/(N·m),respectively.In contrast,the sample added with fine Nb particles has the highest hardness(56.1 HRC),ultimate tensile strength(1892 MPa)and yield strength(1842 MPa),and the volume wear rate of the sample added with coarse Nb particles is reduced by 90%to 1.7×10^(-6) mm^(3)/(N·m).展开更多
The developed 1Cr18Ni9Ti austenitic stainless steel containing 1.63 wt.%B have been characterized by X-ray diffraction(XRD),electron probe microanalyzer(EPMA),optical microscopy(OM),scanning electron microscopy(SEM),e...The developed 1Cr18Ni9Ti austenitic stainless steel containing 1.63 wt.%B have been characterized by X-ray diffraction(XRD),electron probe microanalyzer(EPMA),optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS)and Vickers microhardness measurement.The microstructural evolution and property of high boron stainless steel after solution treatment at the temperature of 1050℃are also investigated.The results show that the main compositions of borides are Fe,Cr and B,and with small amount of Ni,Mn and C elements.Silicon is insoluble in the borides.The hardness of borides is over 1,500 HV.It has been found that borides do not decompose during solution treatment,but part of borides dissolves into the matrix. The effect of increasing the solubility of boron element in the austenitic matrix favours the hardness enhancement by 8.54%.High boron stainless steel has excellent wear resistance in corrosive environment.Lifetime of transfer pipe made of high boron-containing stainless steel is 1.5-1.8 times longer than that of boron-free 1Cr18Ni9Ti stainless steel.展开更多
A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by mea...A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by measurements of pitting corrosion potentials and electrochemical noise during initiation of corrosion pits.The results show that the sputtered coatings with single bcc phase or single fcc structure are more resistant to pitting corrosion than those with bcc plus fcc duplex phase structure.展开更多
The interaction of hydrogen with interface between the precipitates and the martensitie matrix in 18Ni maraging steel has been studied by means of thermal evolution hydrogen technique us- ing gas chromatograph as hydr...The interaction of hydrogen with interface between the precipitates and the martensitie matrix in 18Ni maraging steel has been studied by means of thermal evolution hydrogen technique us- ing gas chromatograph as hydrogen detector.An evolution rate peak has been observed at 451 K.The height of the peak relates to the amount and distribution of the precipitates.The activation energy for hydrogen escaping from the trap sites is 23.2 kJ/mol.展开更多
Laser multiple processing, i.e. laser surface texturing and then Laser Shock Processing (LSP), is a new surface processing technology for the preparation of bionic non-smooth surfaces. Based on engineering bionics, sa...Laser multiple processing, i.e. laser surface texturing and then Laser Shock Processing (LSP), is a new surface processing technology for the preparation of bionic non-smooth surfaces. Based on engineering bionics, samples of bionic non-smooth surfaces of stainless steel 0Crl 8Ni9 were manufactured in the form of reseau structure by laser multiple processing. The mechanical properties (including microhardness, residual stress, surface roughness) and microstructure of the samples treated by laser multiple processing were compared with those of the samples without LSP The results show that the mechanical properties of these samples by laser multiple processing were clearly improved in comparison with those of the samples without LSP The mechanisms underlying the improved surface microhardness and surface residual stress were analyzed, and the relations between hardness, comnressive residual stress and roughness were also presented.展开更多
Superior properties of maraging steels make them suitable for the fabrication of components used for military applications like missile covering, rocket motor casing and ship hulls. Welding is the main process for fab...Superior properties of maraging steels make them suitable for the fabrication of components used for military applications like missile covering, rocket motor casing and ship hulls. Welding is the main process for fabrication of these components, while the maraging steels can be fusion welded using gas tungsten arc welding(GTAW) process. All these fabricated components require longer storage life and a major problem in welds is susceptible to stress corrosion cracking(SCC). The present study is aimed at studying the SCC behaviour of MDN 250(18% Ni) steel and its welds with respect to microstructural changes. In the present study, 5.2 mm thick sheets made of MDN 250 steel in the solution annealed condition was welded using GTAW process. Post-weld heat treatments of direct ageing(480 C for 3 h), solutionizing(815 C for 1 h) followed by ageing and homogenizing(1150 C for 1 h) followed by ageing were carried out. A mixture of martensite and austenite was observed in the microstructure of the fusion zone of solutionized and direct aged welds and only martensite in as-welded condition. Homogenization and ageing treatment have eliminated reverted austenite and elemental segregation. Homogenized welds also exhibited a marginal improvement in the corrosion resistance compared to those in the as-welded, solutionized and aged condition. Constant load SCC test data clearly revealed that the failure time of homogenized weld is much longer compared to other post weld treatments, and the homogenization treatment is recommended to improve the SCC life of GTA welds of MDN 250 Maraging steel.展开更多
The radiation damage of 1Cr18Ni9Ti stainless steel and the Zr-Ti-Al alloy by 200 keV Xe＋ ions bombardment at the fluence ranging from 1×1014 to 8×1015 ions/cm2 has been investigated by conventional transmis...The radiation damage of 1Cr18Ni9Ti stainless steel and the Zr-Ti-Al alloy by 200 keV Xe＋ ions bombardment at the fluence ranging from 1×1014 to 8×1015 ions/cm2 has been investigated by conventional transmission electron microscope, X-ray diffraction line profile analysis （XRDLPA） and nanoindentation. XRDLPA shows that the order of magnitude of dislocation density in both materials remains almost unchanged up to the highest irradiation dose. Selected-area electron diffraction combined with bright and dark field image indicates that 1Cr18Ni9Ti is more easily damaged than the Zr-Ti-Al alloy. With increasing the ions fluence, the radiation damage became more severe in 1Cr18Ni9Ti, accompanied with phase transition and partial amorphization. The nano-hardness was found to increase rapidly with increasing ion fluence till the dose of 1×1015 ions/cm2, and then gradually saturate with dose. The enhancement of hardness in irradiated materials is due to irradiation-induced defects acting as barriers to dislocation motion.展开更多
Among the various grades of commercially available 18 wt. % nickel maraging steels, the one with nominal 0.2% proof strength in the range 1700-1750 MPa is the most commonly used and is distinguished by an excellent co...Among the various grades of commercially available 18 wt. % nickel maraging steels, the one with nominal 0.2% proof strength in the range 1700-1750 MPa is the most commonly used and is distinguished by an excellent combination of high strength and high fracture toughness. The main alloying elements are nickel, cobalt, molybdenum and titanium. The first three of these are present at relatively high concentrations in the chemical composition. The high cost of these metals leads to a high cost of production and this becomes a deterrent to extensive use of the steel. In the present study, an attempt was made to produce the steel by pegging the levels of these alloying elements in the lower half of the specified range. The objective was to save on the raw material cost, while still conforming to the specification. The steel so produced could not, however, attain the specified tensile properties after final heat treatment. The observed behavior is explained based on the role played by the different alloying elements in driving the precipitation hardening reaction.展开更多
The tribological properties of ZrO2 ceramic and 1Cr18Ni9Ti stainless steel rubbing pairs were investigated using a special tribo-tester under different concentrations of hydrogen peroxide (H2O2) solution.The compariso...The tribological properties of ZrO2 ceramic and 1Cr18Ni9Ti stainless steel rubbing pairs were investigated using a special tribo-tester under different concentrations of hydrogen peroxide (H2O2) solution.The comparison analyses of the friction coefficients,worn volume rates,worn particles and surface roughness were conducted under the tested conditions.There were significant differences of the tribological properties of the rubbing pairs in the different concentrations H2O2 solution because of oxidation and corrosion.This research has revealed that the main wear mechanisms between the rubbing pairs are severe adhesive wear,abrasive wear and corrosive wear in the H2O2 solution with different concentrations.A model has been established to assess the most suitable concentration of the H2O2 solution for the tribological properties of the rubbing pairs.The result shows that 50% concentration of the H2O2 solution is the most suitable.The assessment result is consistent with the experimental result.It is believed that the knowledge gained in this study is useful for the optimization of the friction pairs in the extreme condition.展开更多
基金Key-Area Research and Development Program of Guangdong Province(2023B0909020004)Project of Innovation Research Team in Zhongshan(CXTD2023006)+1 种基金Natural Science Foundation of Guangdong Province(2023A1515011573)Zhongshan Social Welfare Science and Technology Research Project(2024B2022)。
文摘Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely used in fields such as injection molding,die casting,and stamping dies.Adding reinforcing particles into steel is an effective means to improve its performance.Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes,and their microstructures and properties were studied.The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined,which is particularly pronounced with fine Nb particles.In addition,element diffusion occurs between the particles and the matrix.The main phases of the base alloy are α-Fe and a small amount of γ-Fe.With the addition of Nb,part of the α-Fe is transformed into γ-Fe,and unmelted Nb phases appear.The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties.After aging treatment,the molten pools and grain boundaries become blurred,grains are further refined,and the interfaces around the particles are thinned.The aging treatment also promotes the formation of reverted austenite.The hardness,ultimate tensile strength,and volumetric wear rate of the base alloy reach 51.9 HRC,1704 MPa,and 17.8×10^(-6) mm^(3)/(N·m),respectively.In contrast,the sample added with fine Nb particles has the highest hardness(56.1 HRC),ultimate tensile strength(1892 MPa)and yield strength(1842 MPa),and the volume wear rate of the sample added with coarse Nb particles is reduced by 90%to 1.7×10^(-6) mm^(3)/(N·m).
基金Supported by the General Program of National Natural Science Foundation of China(Grant No.51679133)The State Key Program of National Natural Science of China(Project No.51439004)
文摘The developed 1Cr18Ni9Ti austenitic stainless steel containing 1.63 wt.%B have been characterized by X-ray diffraction(XRD),electron probe microanalyzer(EPMA),optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS)and Vickers microhardness measurement.The microstructural evolution and property of high boron stainless steel after solution treatment at the temperature of 1050℃are also investigated.The results show that the main compositions of borides are Fe,Cr and B,and with small amount of Ni,Mn and C elements.Silicon is insoluble in the borides.The hardness of borides is over 1,500 HV.It has been found that borides do not decompose during solution treatment,but part of borides dissolves into the matrix. The effect of increasing the solubility of boron element in the austenitic matrix favours the hardness enhancement by 8.54%.High boron stainless steel has excellent wear resistance in corrosive environment.Lifetime of transfer pipe made of high boron-containing stainless steel is 1.5-1.8 times longer than that of boron-free 1Cr18Ni9Ti stainless steel.
文摘A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by measurements of pitting corrosion potentials and electrochemical noise during initiation of corrosion pits.The results show that the sputtered coatings with single bcc phase or single fcc structure are more resistant to pitting corrosion than those with bcc plus fcc duplex phase structure.
文摘The interaction of hydrogen with interface between the precipitates and the martensitie matrix in 18Ni maraging steel has been studied by means of thermal evolution hydrogen technique us- ing gas chromatograph as hydrogen detector.An evolution rate peak has been observed at 451 K.The height of the peak relates to the amount and distribution of the precipitates.The activation energy for hydrogen escaping from the trap sites is 23.2 kJ/mol.
基金supported by the National Natural Science Foundation of China (Grant No.50705038,50735001 and 10804037)the Foundation of Jiangsu Province (Grant No.06-D-023,BK2007512 and BG2007033)+2 种基金The 8th Student Research Train Program of Jiangsu University (Grant No.08A172)the Innovation Program of Graduated Student of Jiangsu Province (Grant No.XM2006-45)the Open Foundation of Jiangsu Key Laboratory of Advanced Numerical Control Technology (Grant No.KXJ07126)
文摘Laser multiple processing, i.e. laser surface texturing and then Laser Shock Processing (LSP), is a new surface processing technology for the preparation of bionic non-smooth surfaces. Based on engineering bionics, samples of bionic non-smooth surfaces of stainless steel 0Crl 8Ni9 were manufactured in the form of reseau structure by laser multiple processing. The mechanical properties (including microhardness, residual stress, surface roughness) and microstructure of the samples treated by laser multiple processing were compared with those of the samples without LSP The results show that the mechanical properties of these samples by laser multiple processing were clearly improved in comparison with those of the samples without LSP The mechanisms underlying the improved surface microhardness and surface residual stress were analyzed, and the relations between hardness, comnressive residual stress and roughness were also presented.
基金Financial assistance from Defence Research Development Organization (DRDO)
文摘Superior properties of maraging steels make them suitable for the fabrication of components used for military applications like missile covering, rocket motor casing and ship hulls. Welding is the main process for fabrication of these components, while the maraging steels can be fusion welded using gas tungsten arc welding(GTAW) process. All these fabricated components require longer storage life and a major problem in welds is susceptible to stress corrosion cracking(SCC). The present study is aimed at studying the SCC behaviour of MDN 250(18% Ni) steel and its welds with respect to microstructural changes. In the present study, 5.2 mm thick sheets made of MDN 250 steel in the solution annealed condition was welded using GTAW process. Post-weld heat treatments of direct ageing(480 C for 3 h), solutionizing(815 C for 1 h) followed by ageing and homogenizing(1150 C for 1 h) followed by ageing were carried out. A mixture of martensite and austenite was observed in the microstructure of the fusion zone of solutionized and direct aged welds and only martensite in as-welded condition. Homogenization and ageing treatment have eliminated reverted austenite and elemental segregation. Homogenized welds also exhibited a marginal improvement in the corrosion resistance compared to those in the as-welded, solutionized and aged condition. Constant load SCC test data clearly revealed that the failure time of homogenized weld is much longer compared to other post weld treatments, and the homogenization treatment is recommended to improve the SCC life of GTA welds of MDN 250 Maraging steel.
基金supported by the National Natural Science Foundation of China(Grant No. 50871057)National Basic Research Program of China (Grant No. 2010CB731601)
文摘The radiation damage of 1Cr18Ni9Ti stainless steel and the Zr-Ti-Al alloy by 200 keV Xe＋ ions bombardment at the fluence ranging from 1×1014 to 8×1015 ions/cm2 has been investigated by conventional transmission electron microscope, X-ray diffraction line profile analysis （XRDLPA） and nanoindentation. XRDLPA shows that the order of magnitude of dislocation density in both materials remains almost unchanged up to the highest irradiation dose. Selected-area electron diffraction combined with bright and dark field image indicates that 1Cr18Ni9Ti is more easily damaged than the Zr-Ti-Al alloy. With increasing the ions fluence, the radiation damage became more severe in 1Cr18Ni9Ti, accompanied with phase transition and partial amorphization. The nano-hardness was found to increase rapidly with increasing ion fluence till the dose of 1×1015 ions/cm2, and then gradually saturate with dose. The enhancement of hardness in irradiated materials is due to irradiation-induced defects acting as barriers to dislocation motion.
文摘Among the various grades of commercially available 18 wt. % nickel maraging steels, the one with nominal 0.2% proof strength in the range 1700-1750 MPa is the most commonly used and is distinguished by an excellent combination of high strength and high fracture toughness. The main alloying elements are nickel, cobalt, molybdenum and titanium. The first three of these are present at relatively high concentrations in the chemical composition. The high cost of these metals leads to a high cost of production and this becomes a deterrent to extensive use of the steel. In the present study, an attempt was made to produce the steel by pegging the levels of these alloying elements in the lower half of the specified range. The objective was to save on the raw material cost, while still conforming to the specification. The steel so produced could not, however, attain the specified tensile properties after final heat treatment. The observed behavior is explained based on the role played by the different alloying elements in driving the precipitation hardening reaction.
基金supported by the Key Basic Research Program of China(Grant No.2007CB607603)the Program for New Century Excellent Talents in University(Grant No.NCET-12-0910)
文摘The tribological properties of ZrO2 ceramic and 1Cr18Ni9Ti stainless steel rubbing pairs were investigated using a special tribo-tester under different concentrations of hydrogen peroxide (H2O2) solution.The comparison analyses of the friction coefficients,worn volume rates,worn particles and surface roughness were conducted under the tested conditions.There were significant differences of the tribological properties of the rubbing pairs in the different concentrations H2O2 solution because of oxidation and corrosion.This research has revealed that the main wear mechanisms between the rubbing pairs are severe adhesive wear,abrasive wear and corrosive wear in the H2O2 solution with different concentrations.A model has been established to assess the most suitable concentration of the H2O2 solution for the tribological properties of the rubbing pairs.The result shows that 50% concentration of the H2O2 solution is the most suitable.The assessment result is consistent with the experimental result.It is believed that the knowledge gained in this study is useful for the optimization of the friction pairs in the extreme condition.
