In order to explore the way to improve the adhesion of the calcium phosphate bioceramic coating to Ti substrate, the CaTiO3 coating was fabricated on Ti substrate by laser cladding （LC） using powders of CaCO3 and Ca...In order to explore the way to improve the adhesion of the calcium phosphate bioceramic coating to Ti substrate, the CaTiO3 coating was fabricated on Ti substrate by laser cladding （LC） using powders of CaCO3 and CaHPO4, and then the composition and microstructure of the coatings were investigated. During LC, CaCO3 can hardly react with Ti, and the coating fabricated using CaCO3 powder is mainly composed of the process of CaO, the decomposition product of CaCO3. Moreover, the coating has a loosened structure and part of it has peeled off from the substrate. CaHPO4 reacts vigorously with Ti, and the coating fabricated using CaHPO4 mainly consists of CaTiO3 which is one of the reaction products between Ti and CaHPO4. Chemical bonding is formed at the interface between coating and substrate, which may enhance the adhesion of the CaTiO3 coating to Ti substrate. Furthermore, CaTiO3 dendrite and eutectic of CaTiO3 and Ca2P2O7 are found on the surface of the coating, implying that a transition can be formed between CaTiO3 and some calcium phosphate bioceramic. So CaTiO3 coating fabricated using CaHPO4 can be a potential candidate to improve the adhesion between calcium phosphate coating and Ti substrate. However, there are also pores and cracks existing in the coating, which may degrade the mechanical properties of the coating.展开更多
Several tensile samples were prepared using laser rapid forming (LRF) with Ti-6Al-4V alloy as powder material, and the samples were annealed. The microstructure and high temperature mechanical properties of laser form...Several tensile samples were prepared using laser rapid forming (LRF) with Ti-6Al-4V alloy as powder material, and the samples were annealed. The microstructure and high temperature mechanical properties of laser formed Ti-6Al-4V alloy through annealing treatment were investigated. The short-term and long-term tensile tests at 350℃were performed. The results show that the microstructure of LRF samples consists of the large columnar priorβgrains which grow epitaxially from the substrate along the deposition direction. There are Widmanstatten a laths in priorβgrains, but a laths in annealed microstructure are coarser, and their aspect ratio is lower than that in as-deposited microstructure. In addition, the priorβgrain boundary is also coarsened and broken off through the annealing treatment. The high temperature mechanical properties of the annealed LRF samples exceed those of casting alloy significantly, especially the stress-rupture lifetime reaches 661.7 h even while the test stress increases from initial value of 490 MPa to the final stress of 800 MPa gradually.展开更多
基金Funded by the National Natural Science Foundation of China (50971102)the National Basic Research Program ("973" Program) of China(2007CB613805)the Programme of Introducing Talents of Discipline to Universities (08040)
文摘In order to explore the way to improve the adhesion of the calcium phosphate bioceramic coating to Ti substrate, the CaTiO3 coating was fabricated on Ti substrate by laser cladding （LC） using powders of CaCO3 and CaHPO4, and then the composition and microstructure of the coatings were investigated. During LC, CaCO3 can hardly react with Ti, and the coating fabricated using CaCO3 powder is mainly composed of the process of CaO, the decomposition product of CaCO3. Moreover, the coating has a loosened structure and part of it has peeled off from the substrate. CaHPO4 reacts vigorously with Ti, and the coating fabricated using CaHPO4 mainly consists of CaTiO3 which is one of the reaction products between Ti and CaHPO4. Chemical bonding is formed at the interface between coating and substrate, which may enhance the adhesion of the CaTiO3 coating to Ti substrate. Furthermore, CaTiO3 dendrite and eutectic of CaTiO3 and Ca2P2O7 are found on the surface of the coating, implying that a transition can be formed between CaTiO3 and some calcium phosphate bioceramic. So CaTiO3 coating fabricated using CaHPO4 can be a potential candidate to improve the adhesion between calcium phosphate coating and Ti substrate. However, there are also pores and cracks existing in the coating, which may degrade the mechanical properties of the coating.
基金Project (50331010) supported by the National Natural Science Foundation of ChinaProject (05XE0131) supported by Talent Cultivating Program of Northwestern Polytechnical University
文摘Several tensile samples were prepared using laser rapid forming (LRF) with Ti-6Al-4V alloy as powder material, and the samples were annealed. The microstructure and high temperature mechanical properties of laser formed Ti-6Al-4V alloy through annealing treatment were investigated. The short-term and long-term tensile tests at 350℃were performed. The results show that the microstructure of LRF samples consists of the large columnar priorβgrains which grow epitaxially from the substrate along the deposition direction. There are Widmanstatten a laths in priorβgrains, but a laths in annealed microstructure are coarser, and their aspect ratio is lower than that in as-deposited microstructure. In addition, the priorβgrain boundary is also coarsened and broken off through the annealing treatment. The high temperature mechanical properties of the annealed LRF samples exceed those of casting alloy significantly, especially the stress-rupture lifetime reaches 661.7 h even while the test stress increases from initial value of 490 MPa to the final stress of 800 MPa gradually.
基金New Century Excellent Talents in University of China (NCET-06-0879)National High Technology Research and Development Program ("863" Program) of China (2006AA03Z0449)National Basic Research Program ("973" Program) of China (2007CB613805)
