Solid carburization was employed to improve the hardness of Ti-6Al-4V alloy and （TiB＋La2O3）/Ti composite. The samples wrapped in graphite powder were placed in sealed quartz tubes, followed by solid carburization a...Solid carburization was employed to improve the hardness of Ti-6Al-4V alloy and （TiB＋La2O3）/Ti composite. The samples wrapped in graphite powder were placed in sealed quartz tubes, followed by solid carburization at 1227 K for 24 h. Microstructure and phase analysis indicated that TiC reinforcements and Ti-C solid solutions were introduced after solid carburization. Moreover, the volume fraction of equiaxedα-Ti phase in diffusion layer decreased obviously with increasing sample depth. Hardness testing results indicated that both the carburized surfaces performed significant improvement of about 100% in micro-hardness compared with untreated materials. The variation of carbon contents with increasing sample depth resulted in a hardened layer of 300 μm in the carburized samples. Meanwhile, slight influence on the internal microstructure and hardness indicated that solid carburization was an effective method in strengthening the surface of titanium alloy and titanium matrix composite.展开更多
In this study, a novel rapid solid carburizing process with a large diffusion depth using nano-diamonds（NDs） was conducted for low carbon steel. Changes of annealed NDs were obtained by Raman spectroscopy and transm...In this study, a novel rapid solid carburizing process with a large diffusion depth using nano-diamonds（NDs） was conducted for low carbon steel. Changes of annealed NDs were obtained by Raman spectroscopy and transmission electron microscopy（TEM）, and the results suggested that the NDs experience a stripping process before a special solid-reaction with surface iron atoms from steel substrate. Onionlike carbon（OLC） derived from the annealed NDs provided broken graphitic ribbons as carbon sources that accelerated the rate of adsorption and diffusion. Examination of the surface layer at equilibrium using TEM and X-ray photoelectron spectroscopy（XPS） also revealed the special state of carbon, and an ultrafine mixed phase microstructure was obtained by rapid solid-phase transformation. As a result, a surface hardened layer with ultrahigh hardness and a smooth transition region were realized. We believe that these kinds of diamond or graphitic structures with high activity states have an important influence not only on adsorption and diffusion but also on this special solid-phase transformation.展开更多
基金Projects(51371114,51501112,51504151)supported by the National Natural Science Foundation of ChinaProject(2012CB619600)supported by the National Basic Research Program of ChinaProject(SAMC14-JS-15-047)supported by the National Engineering and Research Center for Commercial Aircraft Manufacturing,China
文摘Solid carburization was employed to improve the hardness of Ti-6Al-4V alloy and （TiB＋La2O3）/Ti composite. The samples wrapped in graphite powder were placed in sealed quartz tubes, followed by solid carburization at 1227 K for 24 h. Microstructure and phase analysis indicated that TiC reinforcements and Ti-C solid solutions were introduced after solid carburization. Moreover, the volume fraction of equiaxedα-Ti phase in diffusion layer decreased obviously with increasing sample depth. Hardness testing results indicated that both the carburized surfaces performed significant improvement of about 100% in micro-hardness compared with untreated materials. The variation of carbon contents with increasing sample depth resulted in a hardened layer of 300 μm in the carburized samples. Meanwhile, slight influence on the internal microstructure and hardness indicated that solid carburization was an effective method in strengthening the surface of titanium alloy and titanium matrix composite.
基金supported by the National Natural Science Foundation of China (No. 51641109)the National Basic Research Program of China (No. 2014CB046303)the Fundamental Research Funds for the Central Universities of China (Grant No. 2015XKQY01)
文摘In this study, a novel rapid solid carburizing process with a large diffusion depth using nano-diamonds（NDs） was conducted for low carbon steel. Changes of annealed NDs were obtained by Raman spectroscopy and transmission electron microscopy（TEM）, and the results suggested that the NDs experience a stripping process before a special solid-reaction with surface iron atoms from steel substrate. Onionlike carbon（OLC） derived from the annealed NDs provided broken graphitic ribbons as carbon sources that accelerated the rate of adsorption and diffusion. Examination of the surface layer at equilibrium using TEM and X-ray photoelectron spectroscopy（XPS） also revealed the special state of carbon, and an ultrafine mixed phase microstructure was obtained by rapid solid-phase transformation. As a result, a surface hardened layer with ultrahigh hardness and a smooth transition region were realized. We believe that these kinds of diamond or graphitic structures with high activity states have an important influence not only on adsorption and diffusion but also on this special solid-phase transformation.
