A SiC_(nws)/HfC-SiC coating was fabricated by a two-step chemical vapor deposition.After introducing SiC nanowires,the fracture toughness of HfC-SiC coating increases by 228%.After ablation under oxyacetylene torch fo...A SiC_(nws)/HfC-SiC coating was fabricated by a two-step chemical vapor deposition.After introducing SiC nanowires,the fracture toughness of HfC-SiC coating increases by 228%.After ablation under oxyacetylene torch for 60s,a bone-like HfO_(2) reticular structure was formed in the central ablation area.Interestingly,a novel Hf-Si-O wire-drawing phenomenon was happened in the transition area of ablated SiC_(nws)/HfC-SiC coating,providing a new toughness mechanism under ablation environment.Moreover,HfO_(2) precipitated from Hf-Si-O glass wires to generate nanocrystalline grains during ablation,which explains the formation of bone-like HfO_(2) reticular structure observed from central ablation area.展开更多
The suitable test equipment for wire-drawing was designed. Wire-drawing tests were carried on with this equipment for TiC/Al2O3 ceramic wire-drawing die. Effect of lubrication medium and drawing velocity on the drawin...The suitable test equipment for wire-drawing was designed. Wire-drawing tests were carried on with this equipment for TiC/Al2O3 ceramic wire-drawing die. Effect of lubrication medium and drawing velocity on the drawing force was investigated. The wear mechanisms of the ceramic drawing dies were investigated. Worn bore surfaces of the ceramic drawing dies were examined by scanning electron microscopy. The results show that lubricant media have great influence on the drawing force. The drawing force is the smallest when a grease lubricant is used. But alteration of drawing velocity has scarcely any influence on the drawing force. Detailed observations and analyses of the die wear surface reveal that the most common failure of the ceramic drawing die is the wear in the invariable zone and bearing zone owing to the greater press stresses. Abrasive and adhesive wear are found to be the predominant wear mechanisms for ceramic drawing die.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.51572223,51221001 and 51872237Natural Science Basic Research Plan in Shaanxi Province of China No.2017JM5098.
文摘A SiC_(nws)/HfC-SiC coating was fabricated by a two-step chemical vapor deposition.After introducing SiC nanowires,the fracture toughness of HfC-SiC coating increases by 228%.After ablation under oxyacetylene torch for 60s,a bone-like HfO_(2) reticular structure was formed in the central ablation area.Interestingly,a novel Hf-Si-O wire-drawing phenomenon was happened in the transition area of ablated SiC_(nws)/HfC-SiC coating,providing a new toughness mechanism under ablation environment.Moreover,HfO_(2) precipitated from Hf-Si-O glass wires to generate nanocrystalline grains during ablation,which explains the formation of bone-like HfO_(2) reticular structure observed from central ablation area.
基金Project(B0614) supported by the Natural Science Foundation of University of Jinan, ChinaProject(20030422105) supported by the Specialized Research Fund for Doctoral Program of Higher Education, China+1 种基金Project(Y2004F08) supported by the Natural Science Foundation of Shandong Province, ChinaProject(NCET-04-0622) supported by the Program for New Century Excellent Talents in University, China.
文摘The suitable test equipment for wire-drawing was designed. Wire-drawing tests were carried on with this equipment for TiC/Al2O3 ceramic wire-drawing die. Effect of lubrication medium and drawing velocity on the drawing force was investigated. The wear mechanisms of the ceramic drawing dies were investigated. Worn bore surfaces of the ceramic drawing dies were examined by scanning electron microscopy. The results show that lubricant media have great influence on the drawing force. The drawing force is the smallest when a grease lubricant is used. But alteration of drawing velocity has scarcely any influence on the drawing force. Detailed observations and analyses of the die wear surface reveal that the most common failure of the ceramic drawing die is the wear in the invariable zone and bearing zone owing to the greater press stresses. Abrasive and adhesive wear are found to be the predominant wear mechanisms for ceramic drawing die.
