The effect of aging temperature on erosion corrosion (E-C) behavior of 17-4PH stainless steels in dilute sulphuric acid slurry containing solid particles was studied by using self-made rotating E-C apparatus. The ef...The effect of aging temperature on erosion corrosion (E-C) behavior of 17-4PH stainless steels in dilute sulphuric acid slurry containing solid particles was studied by using self-made rotating E-C apparatus. The effect of impact velocity on EC behavior of 17 4PH steels at different aging temperatures was analyzed. Surface micrographs of the specimens after E C test were observed by using scanning electron microscope (SEM). The results showed that under the condition of the same solution heat treatment, when aging temperature ranged from 400 ℃ to 610℃, the hardness reached the highest value near the temperature 460℃. The characteristics of E-C for 17-4PH stainless steels at different aging temperatures were as follows: pure erosion (wear) was dominant, corrosion was subordinate and at the same time corrosion promoted erosion. The effect of aging temperature on E-C rate of 17-4PH steels was not significant at low impact velocity, but it was found that E-C resistance of 17-4PH steels aged near 460℃ was the most excellent due to the best precipitation strengthening effect of fine and dispersed e-Cu phase. With a prerequisite of appropriate corrosion resistance, the precipitation hardening could significantly improve the E-C resistance of the materials.展开更多
The feedstock based on the binder 65%PW-30%EVA-5%SA has the best general rheological properties for the 17-4PH stainless steel powder. The 17-4PH stainless steel compacts sintered at 1 380 ℃ for 90 min have the best ...The feedstock based on the binder 65%PW-30%EVA-5%SA has the best general rheological properties for the 17-4PH stainless steel powder. The 17-4PH stainless steel compacts sintered at 1 380 ℃ for 90 min have the best mechanical properties and the good microstructure with homogeneously distributed pore structure and the moderate-sized grains. Whereas the compacts sintered for 60 min and 120 min show an inadequate and an over-sintered microstructure respectively. The compacts sintered at 1380 ℃ for 90 min have the density of 7.70 g/cm^3, the strength of 1 275 MPa, the elongation of 5%, and hardness of HRC36. With the increase of sintering temperature, the density, strength and hardness increase, while the elongation decreases. The 17-4PH stainless steel has good corrosion resistance, showing an activation-passivation polarization curve. But the passivation potential range is narrow and the spot corrosion potential is low, indicating a low anti-spot corrosive properties.展开更多
17-4 precipitation-hardened(PH)stainless steel(SS)exhibits high strength and good corrosion resistance via Cu-precipitation hardening.Unlike conventional wrought 17-4PH SS,Cu segregation andε-Cu pre-cipitates are obs...17-4 precipitation-hardened(PH)stainless steel(SS)exhibits high strength and good corrosion resistance via Cu-precipitation hardening.Unlike conventional wrought 17-4PH SS,Cu segregation andε-Cu pre-cipitates are observed in additively manufactured(AM)17-4PH SS owing to the repeated rapid cooling after heating,which characterizes the AM process.In this study,solution treatment was conducted under various temperatures(1,000,1,050,1,100,and 1,200℃)and durations(1,2,4,and 8 h)to minimize the negative effects of Cu segregation andε-Cu precipitates on precipitation hardening.The mechanical prop-erties and microstructures of each condition for the Cu precipitation behavior were examined.Although theε-Cu precipitates did not disappear after solution treatment,the average diameter of theε-Cu precipi-tates tended to decrease with increasing solution treatment temperature and duration.Therefore,solution treatment at a temperature of 1,200℃ for 8 h was the best,resulting in improved strength compared to the conventional solution treatment at 1,050℃.Solution treatment on at least 1,100℃ is effective in AM.展开更多
The segregation of Cu and Ni in a 17-4PH stainless steel piston rod has been confirmed to be responsible for the cracking after heat treatment.Further investigation showed that the segregation zone was composed of thr...The segregation of Cu and Ni in a 17-4PH stainless steel piston rod has been confirmed to be responsible for the cracking after heat treatment.Further investigation showed that the segregation zone was composed of three layers,namely the fine grain martensitic layer,the coarse grain martensitic layer and the coarse grain austenitic layer from the matrix to the crack surface.Three button ingots with the same chemical compositions as those three layers have been prepared to evaluate the grain size distribution,microstructure and mechanical properties.The effects of Cu and Ni segregation on the microstructures of those three layers have been explored by thermodynamic calculation.Based on the microstructure and mechanical properties results,an intensive understanding of the cracking in the segregation zone was therefore reached.展开更多
The relationship between the microstructure transformation of type 17-4 PH stainless steel and the aging hardening behavior was investigated. The results showed that, when 17-4 PH stainless steel aging at 595℃, the b...The relationship between the microstructure transformation of type 17-4 PH stainless steel and the aging hardening behavior was investigated. The results showed that, when 17-4 PH stainless steel aging at 595℃, the bulk hardness of samples attains its peak value (42.5 HRC) for about 20 min, and then decreases at all time. TEM revealed the microstructure corresponding with peak hardness is that the fine spheroid-shape copper with the fcc crystal structure and the fiber-shape secondary carbide M23C6 precipitated from the lath martensite matrix. Both precipitations of copper and M23C6 are the reasons for strengthening of the alloy at this temperature. With the extension of holding time at this temperature, the copper and secondary carbide grow and lose the coherent relationship with the matrix, so the bulk hardness of samples decreases.展开更多
The aim of this investigation is to reveal the influence of rare earths(RE) addition on mechanical properties of plasma nitrocarburized 17-4PH steel.The nitrocarburized layers were characterized by optical microscope,...The aim of this investigation is to reveal the influence of rare earths(RE) addition on mechanical properties of plasma nitrocarburized 17-4PH steel.The nitrocarburized layers were characterized by optical microscope,scanning electron microscope equipped with energy dispersive X-ray analyzer,X-ray diffractometer,microhardness tester and pin-on-disc tribometer.The results showed that RE atoms could diffuse into the surface layer of 17-4PH steel plasma nitrocarburized at 500 °C for 4 h and did not change the ...展开更多
文摘The effect of aging temperature on erosion corrosion (E-C) behavior of 17-4PH stainless steels in dilute sulphuric acid slurry containing solid particles was studied by using self-made rotating E-C apparatus. The effect of impact velocity on EC behavior of 17 4PH steels at different aging temperatures was analyzed. Surface micrographs of the specimens after E C test were observed by using scanning electron microscope (SEM). The results showed that under the condition of the same solution heat treatment, when aging temperature ranged from 400 ℃ to 610℃, the hardness reached the highest value near the temperature 460℃. The characteristics of E-C for 17-4PH stainless steels at different aging temperatures were as follows: pure erosion (wear) was dominant, corrosion was subordinate and at the same time corrosion promoted erosion. The effect of aging temperature on E-C rate of 17-4PH steels was not significant at low impact velocity, but it was found that E-C resistance of 17-4PH steels aged near 460℃ was the most excellent due to the best precipitation strengthening effect of fine and dispersed e-Cu phase. With a prerequisite of appropriate corrosion resistance, the precipitation hardening could significantly improve the E-C resistance of the materials.
文摘The feedstock based on the binder 65%PW-30%EVA-5%SA has the best general rheological properties for the 17-4PH stainless steel powder. The 17-4PH stainless steel compacts sintered at 1 380 ℃ for 90 min have the best mechanical properties and the good microstructure with homogeneously distributed pore structure and the moderate-sized grains. Whereas the compacts sintered for 60 min and 120 min show an inadequate and an over-sintered microstructure respectively. The compacts sintered at 1380 ℃ for 90 min have the density of 7.70 g/cm^3, the strength of 1 275 MPa, the elongation of 5%, and hardness of HRC36. With the increase of sintering temperature, the density, strength and hardness increase, while the elongation decreases. The 17-4PH stainless steel has good corrosion resistance, showing an activation-passivation polarization curve. But the passivation potential range is narrow and the spot corrosion potential is low, indicating a low anti-spot corrosive properties.
基金This work was funded by Yangyoung Foundation and supported by the Technology Innovation Program(grant No.20009815,Development of DfAM-based 3D printing technology for lightweight and integrated aerospace parts)funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea).
文摘17-4 precipitation-hardened(PH)stainless steel(SS)exhibits high strength and good corrosion resistance via Cu-precipitation hardening.Unlike conventional wrought 17-4PH SS,Cu segregation andε-Cu pre-cipitates are observed in additively manufactured(AM)17-4PH SS owing to the repeated rapid cooling after heating,which characterizes the AM process.In this study,solution treatment was conducted under various temperatures(1,000,1,050,1,100,and 1,200℃)and durations(1,2,4,and 8 h)to minimize the negative effects of Cu segregation andε-Cu precipitates on precipitation hardening.The mechanical prop-erties and microstructures of each condition for the Cu precipitation behavior were examined.Although theε-Cu precipitates did not disappear after solution treatment,the average diameter of theε-Cu precipi-tates tended to decrease with increasing solution treatment temperature and duration.Therefore,solution treatment at a temperature of 1,200℃ for 8 h was the best,resulting in improved strength compared to the conventional solution treatment at 1,050℃.Solution treatment on at least 1,100℃ is effective in AM.
基金financially sponsored by National Natural Science Foundation of China(Grant No.51201160)Youth Innovation Promotion Association of Chinese Academy of Sciences(2017233)Science and Technology Innovation Foundation from Institute of Metal Research,Chinese Academy of Sciences(Grant No.2015-ZD04)
文摘The segregation of Cu and Ni in a 17-4PH stainless steel piston rod has been confirmed to be responsible for the cracking after heat treatment.Further investigation showed that the segregation zone was composed of three layers,namely the fine grain martensitic layer,the coarse grain martensitic layer and the coarse grain austenitic layer from the matrix to the crack surface.Three button ingots with the same chemical compositions as those three layers have been prepared to evaluate the grain size distribution,microstructure and mechanical properties.The effects of Cu and Ni segregation on the microstructures of those three layers have been explored by thermodynamic calculation.Based on the microstructure and mechanical properties results,an intensive understanding of the cracking in the segregation zone was therefore reached.
基金This work was financially supported by the Key Nuclear Fuel and Nuclear Materials Laboratory of China(No.51481080104ZS8501).
文摘The relationship between the microstructure transformation of type 17-4 PH stainless steel and the aging hardening behavior was investigated. The results showed that, when 17-4 PH stainless steel aging at 595℃, the bulk hardness of samples attains its peak value (42.5 HRC) for about 20 min, and then decreases at all time. TEM revealed the microstructure corresponding with peak hardness is that the fine spheroid-shape copper with the fcc crystal structure and the fiber-shape secondary carbide M23C6 precipitated from the lath martensite matrix. Both precipitations of copper and M23C6 are the reasons for strengthening of the alloy at this temperature. With the extension of holding time at this temperature, the copper and secondary carbide grow and lose the coherent relationship with the matrix, so the bulk hardness of samples decreases.
基金supported by the National Natural Science Foundation of China (50871035)the Ph.D. Programs Foundation of Ministry of Education of China (20060213017)
文摘The aim of this investigation is to reveal the influence of rare earths(RE) addition on mechanical properties of plasma nitrocarburized 17-4PH steel.The nitrocarburized layers were characterized by optical microscope,scanning electron microscope equipped with energy dispersive X-ray analyzer,X-ray diffractometer,microhardness tester and pin-on-disc tribometer.The results showed that RE atoms could diffuse into the surface layer of 17-4PH steel plasma nitrocarburized at 500 °C for 4 h and did not change the ...