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宽带激光熔覆梯度生物陶瓷复合涂层及其生物相容性
Gradient Bioceramic Composite Coating Fabricated by Wide-Band Laser Cladding and Its Biocompatibility
【作者】 刘其斌；
【导师】 董闯；
【作者基本信息】 大连理工大学 ， 材料科学与工程， 2005， 博士
【摘要】 为了消除激光熔覆过程中基材与生物陶瓷涂层之间的热应力,提高涂层与基材的结合强度,设计了一种梯度涂层,采用宽带激光熔覆技术在Ti-6Al-4V合金表面成功地制备了梯度生物陶瓷复合涂层,并在以下几个方面开展了研究工作。以热力学和动力学的研究结果为指导,通过宽带激光熔覆工艺参数对生物陶瓷复合涂层组织形貌及烧结性影响的研究,确定最佳工艺参数为:宽带激光输出功率P=2. 5kW,扫描速度V=150mm/min,光斑尺寸D=16 mm×2mm;通过对瞬态温度场的数值模拟,给出了温度场的分布。结果表明,即使在熔覆的最后阶段即t=11. 6s时,熔池的最高温度(1919℃)也低于含HA生物陶瓷涂复合涂层理论计算的热力学温度(1927℃)。从而验证了最佳工艺参数下可以获得含HA的生物陶瓷复合涂层。研究发现,Y2O3含量影响着生物陶瓷复合涂层中HA及β-TCP的形成,随着Y2O3的增加,复合涂层中HA+β-TCP的含量逐渐增加,当Y2O3含量处于0. 4-0. 6wt.%范围时,复合涂层中HA+β-TCP的含量最大,当Y2O3含量为0. 8wt.%时,其合成HA+β-TCP的数量反而下降。并对Y2O3含量对催化合成活性钙磷基磷灰石相数量进行了讨论。运用XRD、SEM、EDS、EPA现代微观分析技术,系统地研究了梯度生物陶瓷涂层的组织结构,结果表明,涂层分为基材、合金化层以及生物陶瓷层三个层次,各层的结合界面处无裂纹,且界面呈犬牙交错的组织结构。合金层中基底组织为Ti(Al,P,Fe,V),白色的共晶组织为Fe2Ti4O+AlV3,白色颗粒状组织为Al3V0. 333Ti0. 666。生物陶瓷涂层中基底组织为CaO+CaTiO3+HA,灰色颗粒相为α-TCP和β-TCP,白色颗粒相为TiO。生物陶瓷涂层表面形成的类珊瑚礁和短杆堆积结构,将会增加生物陶瓷涂层与骨组织的生物活性。力学性能研究结果表明,宽带激光熔覆的梯度生物陶瓷复合涂层与钛合金基体的结合强度在38. 8 MPa以上。Y2O3含量为0. 6wt.%时,生物陶瓷层和合金化层的显微硬度值均达到最大,分别为1062HV0. 1和1405HV0. 4。生物陶瓷复合涂层试样平均拉伸强度为767. 83MPa,平均弯曲强度值为1671. 65 MPa,涂层弹性模量平均值为13. 98GPa,与人体致密骨的弹性模量相当接近。添加Y2O3的梯度生物陶瓷涂层的断裂韧性值在3. 89-6. 46 MPa·m1/2之间,表明具有良好的强韧
【Abstract】 To eliminate thermal stress during laser cladding and to raise bonding strength between substrate and coating, composition gradient coatings are designed and fabricated by using wide-band laser cladding technique on a Ti alloy.Guided by thermodynamic and kinetic calculations, the effects of technical parameters of wide-band laser cladding on morphology and sinterability of the bioceramic composite coatings are revealed and the optimized working parameters are obtained, i.e. laser output power P=2.5kw, scanning velocity V=150mm/min, laser beam size D=16mm×2mm. A numerical simulation of the transient temperature field shows that the highest temperature in the melting pool （1919℃） is lower than the upper limit （1927℃） for the formation of HA bioceramic, which validates the feasibility of using the present technique to obtain bioceramic composite coatings.The Rare Earth oxide addition on the formation of HA and 3 -TCP in the bioceramic composite coatings is investigated. When the Y2O3 content falls in the range of 0.4 0.6wt.%, the HA and β -TCP phase contents are the highest. However, above 0.8wt.% Y2O3, the HA and β -TCP phase contents in coatings decrease. The mechanism of such a rare earth catalyzing effect is discussed.The gradient bioceramic composite coatings consist of an alloyed transition layer and the bioceramic coating. The alloyed transition layer is comprised of Ti（Al,P,Fe,V） as the matrix phase, a white eutectic structure Fe2Ti4O+AlV3 and white particles Al3V0.333Ti0.666- In the bioceramic coatings, the matrix phase is mainly comprised of HA ,CaTiO3 and CaO, embedded with α -TCP, β -TCP and TiO particlesThe bonding strength between the coating and the substrate is fairly high, above 38.8MPa. The highest microhardness is obtained for the coating containing 0.6wt.%Y2O3 1062HV0.1 and 1405HV0.1, respectively at the bioceramic coating and the alloyed transition layer. The average tensile strength, bending strength, and elastic modules of the bioceramic coatings are 767.83MPa, 1671.65MPa, and 13.98GPa, respectively. It is particularly noted that the elastic modules is quite closer to that of human bone. The fracture toughness ranges from 3.89 to ,6.46 MPa · m1/2. The wear resistance of the gradient bioceramic coating is excellent.Acute toxicity experiment of mice indicates that after muscle injection of the largest medicine amount, the mice do not show obvious acute toxicity reaction. The implanting into rabbits femur for 1, 2 and 3 months does not exhibit hypersusceptibility , rejection and pathological changes. The amount of leucocyte andneutral cell is normal and the value of Ca2+ and P（PO3’,HPO42",H2PO4’） nearly keeps equivalent to that of normal animals. In addition, carbamide and CO2 combination rate is in approximately normal level, which demonstrates that the bioceramic coating has a good biocompatibility.After the implantation of the bioceramic coatings into dogs’ femur for 6, 12, and 24 weeks, hypersusceptibility , rejection and pathological changes are not found. No fiber cyst, necrosis of bone tissue and chronic inflammation obviously appear through slice observation of hard tissues. The bioceramic coating with different ratios of Ca : P have different abilities to induce osteogenesis. At Ca:P=1.4 and 0.6wt.% Y2O3, the bioceramic coating totally combines with new bones after implanted for 6 weeks, while other coatings are not totally linked with new bones, which indicates that this sample is of best bioactivity and biocompatibility.