Hovsepian Papken Ehiasar, Sugumaran Arunprabhu Arunachalam, Rainforth Mark, Qi Jiahui, Khan Imran, Ehiasarian Arutiun Papken
National HIPIMS Technology Centre, Materials and Engineering Research Institute, Sheffield Hallam University, United Kingdom.
National HIPIMS Technology Centre, Materials and Engineering Research Institute, Sheffield Hallam University, United Kingdom.
J Mech Behav Biomed Mater. 2022 Aug;132:105267. doi: 10.1016/j.jmbbm.2022.105267. Epub 2022 May 10.
In recent years significant progress has been made in the application of various ceramic, namely Metal nitride (MeN) functional coatings to engineer the surfaces of medical implants utilising metal-on-metal (MoM) articulation. This article reports on the load bearing capacity and structural response of TiN/NbN superlattice coatings deposited on medical grade CoCrMo alloy substrate under the application of localised load and the subsequent crack formation mechanism. The coatings have been deposited by mixed High Power Impulse Magnetron Sputtering-Unbalanced Magnetron Sputtering (HIPIMS-UBM) process. In the case of TiN/NbN coating deposited on CoCrMo substrate where E/E is as high as 1.81 indicating that the substrate does not provide the necessary load bearing support for the brittle thin film, the utilisation of the Berkovich indentation technique proved to be a potent approach to study coating material as well as structural response to applied concentrated load. FIB/SEM analyses of the indented coatings revealed that in the hard-on-soft material systems cracks will initiate due to sub-coating substrate deformation and then propagate towards the coating surface. The FIB/SEM and low magnification XTEM analysis showed that an exceptionally strong TiN/NbN coating substrate adhesion bonding was achieved due to the utilisation of the HIPIMS pre-treatment. High resolution XTEM analyses revealed, for the first time, that during the indentation a collective rotation and alignment of the individual layers of the superlattice stack takes place without compromising coatings integrity which is clear evidence for the exeptionally high coating fracture toughness. The high toughness of the superlattice structured TiN/NbN coatings combined with their exceptionally high adhesion on madical grade CoCrMo ranks them as a strong candidate for medical implant applications.
近年来，在应用各种陶瓷，即金属氮化物（MeN）功能涂层来设计利用金属对金属（MoM）关节连接的医用植入物表面方面取得了重大进展。本文报道了沉积在医用级CoCrMo合金基底上的TiN/NbN超晶格涂层在局部加载作用下的承载能力和结构响应以及随后的裂纹形成机制。这些涂层是通过混合高功率脉冲磁控溅射 - 非平衡磁控溅射（HIPIMS - UBM）工艺沉积的。在沉积在CoCrMo基底上的TiN/NbN涂层的情况下，其中E/E高达1.81，表明基底不能为脆性薄膜提供必要的承载支撑，利用贝氏压痕技术被证明是研究涂层材料以及对施加的集中载荷的结构响应的有效方法。对压痕涂层的FIB/SEM分析表明，在硬对软材料系统中，裂纹将由于涂层下基底的变形而引发，然后向涂层表面扩展。FIB/SEM和低倍率XTEM分析表明，由于采用了HIPIMS预处理，实现了TiN/NbN涂层与基底之间异常强的粘结。高分辨率XTEM分析首次揭示，在压痕过程中，超晶格堆叠的各个层发生集体旋转和排列，而不会损害涂层的完整性，这是涂层具有极高断裂韧性的明确证据。超晶格结构的TiN/NbN涂层的高韧性及其在医用级CoCrMo上的极高附着力使其成为医用植入物应用的有力候选材料。
