The effects of charging and outgassing on the friction and wear of Ni-P amorphous and nanocrystalline coatings were studied under ambient humidity and temperature.The results indicate that hydrogen charging can greatl...The effects of charging and outgassing on the friction and wear of Ni-P amorphous and nanocrystalline coatings were studied under ambient humidity and temperature.The results indicate that hydrogen charging can greatly decrease the volume loss during friction and increase the wear durability.However,the wear durability can be restored after outgassing.There are many cracks on the brittle nanocrystalline before charging,and no crack appears after charging,but there are only a few cracks on the outgassed sample.This indicates that hydrogen charging can inhibit the crack formation during friction for the brittle Ni-P nanocrystalline.For the charged sample,after the surface layer was removed by polishing,the wear track and the friction coefficient are consistent with those of an uncharged sample.The friction coefficient of the charged amorphous coating is very small within the first 140 s and then increases suddenly to the value corresponding to the uncharged sample.The absorbed surface layer lubricates the surface,reduces the friction coefficient,and improves the wear durability.展开更多
The formation condition of hydrogen blister in 18Ni maraging steel without any inner or external stress was investigated. The results show that the critical diffusible hydrogen concentration of a blister forming is ab...The formation condition of hydrogen blister in 18Ni maraging steel without any inner or external stress was investigated. The results show that the critical diffusible hydrogen concentration of a blister forming is about 1.4×10^-5 , which is corresponding to the current density of 30 mA/cm^2 during cathodic charging in a sodium hydroxide solution. For a 0.1 cm thick sample, no matter the current density is equal to or much larger than the critical value, it spends at least about 132 h to form a hydrogen blister when hydrogen charging in single direction. It is approxi- mately equal to the time for hydrogen atom to diffuse throughout the sample, which exactly depends on the hydrogen diffusion coefficient and the penetration depth. The very first clear suggestion was reported that the incubation period for hydrogen blister nucleation was necessary. According to the Fick＇s laws, calculations show that the normalized hydrogen concentration in the escaping surface almost reaches 0.96 times of the charging surface, which means that the diffusion almost reaches a dynamic balance. A model was illustrated to describe the competitive relationship between hydrogen diffusion and blister formation.展开更多
基金supported by the National Natural Science Foundation of China(No.50771107)the Major State Basic Research Development Program of China(No.2007CB714700)
文摘The effects of charging and outgassing on the friction and wear of Ni-P amorphous and nanocrystalline coatings were studied under ambient humidity and temperature.The results indicate that hydrogen charging can greatly decrease the volume loss during friction and increase the wear durability.However,the wear durability can be restored after outgassing.There are many cracks on the brittle nanocrystalline before charging,and no crack appears after charging,but there are only a few cracks on the outgassed sample.This indicates that hydrogen charging can inhibit the crack formation during friction for the brittle Ni-P nanocrystalline.For the charged sample,after the surface layer was removed by polishing,the wear track and the friction coefficient are consistent with those of an uncharged sample.The friction coefficient of the charged amorphous coating is very small within the first 140 s and then increases suddenly to the value corresponding to the uncharged sample.The absorbed surface layer lubricates the surface,reduces the friction coefficient,and improves the wear durability.
基金Item Sponsored by National Natural Science Foundation of China(51571029,51071025)National Basic Research Program of China(2014CB643301)
文摘The formation condition of hydrogen blister in 18Ni maraging steel without any inner or external stress was investigated. The results show that the critical diffusible hydrogen concentration of a blister forming is about 1.4×10^-5 , which is corresponding to the current density of 30 mA/cm^2 during cathodic charging in a sodium hydroxide solution. For a 0.1 cm thick sample, no matter the current density is equal to or much larger than the critical value, it spends at least about 132 h to form a hydrogen blister when hydrogen charging in single direction. It is approxi- mately equal to the time for hydrogen atom to diffuse throughout the sample, which exactly depends on the hydrogen diffusion coefficient and the penetration depth. The very first clear suggestion was reported that the incubation period for hydrogen blister nucleation was necessary. According to the Fick＇s laws, calculations show that the normalized hydrogen concentration in the escaping surface almost reaches 0.96 times of the charging surface, which means that the diffusion almost reaches a dynamic balance. A model was illustrated to describe the competitive relationship between hydrogen diffusion and blister formation.
