Lynn A K, DuQuesnay D L
Department of Bioartificial Organs, Institute for Frontier Medical Sciences, Kyoto University, Japan.
Biomaterials. 2002 May;23(9):1937-46. doi: 10.1016/s0142-9612(01)00321-0.
The present investigation examines the effect of coating thickness on the fatigue behaviour of hydroxyapatite (HA)-coated Ti-6Al-4V. Uniaxial fatigue tests were conducted on grit blasted Ti-6Al-4V coupons with HA coatings deposited by atmospheric plasma-spray at thicknesses of 0, 25, 50, 75, 100, and 150 microm, as well as on grit blasted specimens that had received a stress relieving heat treatment. Coupons with 150 microm HA coatings were shown to have significantly decreased fatigue resistances, with lives similar to those of the stress relieved specimens, while coatings of thickness 25-100 microm were found to have no affect on fatigue resistance. Residual stresses generated during deposition, cracks propagating towards the substrate from within the coating, and stress relief due to heat inputs from the spraying process were all considered with respect to their potential effects on fatigue behaviour. Stress relief in the substrate due to enhanced heat transfer mechanisms was identified as the most likely source of the observed reductions in substrate fatigue life in the 150 microm coupons.
本研究考察了涂层厚度对羟基磷灰石（HA）涂层Ti-6Al-4V疲劳行为的影响。对经喷砂处理的Ti-6Al-4V试样进行了单轴疲劳试验，这些试样上通过大气等离子喷涂沉积了厚度为0、25、50、75、100和150微米的HA涂层，同时也对经过消除应力热处理的喷砂试样进行了试验。结果表明，具有150微米HA涂层的试样疲劳抗力显著降低，其寿命与消除应力的试样相似，而厚度为25 - 100微米的涂层对疲劳抗力没有影响。考虑了沉积过程中产生的残余应力、涂层内部向基体扩展的裂纹以及喷涂过程中的热输入引起的应力释放对疲劳行为的潜在影响。由于强化传热机制导致的基体应力释放被确定为150微米涂层试样中观察到的基体疲劳寿命降低的最可能原因。
