Development and characterisation of novel ceramic-metal composites

陶瓷-金属复合材料（或陶瓷）结合了两种成分的良好机械性能，即陶瓷的高硬度和耐磨性以及金属的延展性和韧性。因此，陶瓷被用于各种应用，包括：运输（船舶，汽车，航空航天），化学加工，纸浆和纸张加工，废物焚烧等。几十年来，碳化钨/钴“硬质合金”（WC/Co）一直是工业应用陶瓷的主要例子。然而，这些材料的耐腐蚀和耐高温氧化（即高于~500°C）能力差，以及对高温强度退化的敏感性，限制了它们的应用。最近，申请人在工作中开发了基于碳化物或硼化物陶瓷与球墨镍或铁铝化物结合的新一代高级陶瓷。特别是，碳化钛/铝镍合金（TiC/Ni3Al）陶瓷在室温下表现出与WC/Co相似的机械性能，但在高温下表现出更优异的性能。例如，已经证明TiC/Ni3Al陶瓷在1000°C时实际上比室温下更强，而它们的质量也不到WC/Co的一半。在提出的工作中，这些材料的新变体将基于合金碳氮化钛（Ti(C，N)）基体以及纳米结构TiC基体开发。将进行润湿和熔体渗透行为的基础研究，以评估加工参数。复合材料的接触疲劳响应将在室温和高温下的赫兹压痕加载条件下进行测定。本文将提出一种基于聚焦离子束切除缩进区域的新方法来评估弹性/塑性变形。氧化行为将通过热重分析和微观结构表征来确定。此外，将评估新的粘合剂，使用基于溅射的组合搜索方法进行初步筛选，并结合纳米压痕的结果库。

Ceramic-metal composites (or cermets) combine the favourable mechanical properties of both constituents, namely the high hardness and wear resistance of ceramics and the ductility and toughness associated with metals. Consequently, cermets are used in diverse applications including: transportation (marine, automotive, aerospace), chemical processing, pulp and paper processing, waste incineration, etc.. For many decades tungsten carbide/cobalt 'hardmetals' (WC/Co) have been the primary example of industrially applied cermets. However, these materials are limited in application by their poor resistance to corrosion and high temperature oxidation (i.e. above ~500°C), as well as their susceptibility to high temperature strength degradation. Recently, a new generation of advanced cermets, based on either carbide or boride ceramics combined with ductile nickel or iron aluminides, has been developed in work conducted by the applicant. In particular, titanium carbide/nickel aluminide (TiC/Ni3Al) cermets exhibit generally similar mechanical properties to WC/Co at room temperature, but vastly superior elevated temperature behaviour. For example, it has been demonstrated that TiC/Ni3Al cermets are actually stronger at 1000°C than at room temperature, while they also have less than half the mass of WC/Co. In the proposed work, novel variants of these materials will be developed, based on alloyed titanium carbonitride (Ti(C,N)) matrices, as well as nano-structured TiC matrices. Fundamental studies of the wetting and melt-infiltration behaviour will be conducted to assess processing parameters. The contact fatigue response of the composites will be determined under Hertzian indentation loading conditions, at both room and elevated temperature. A novel method based on focused ion beam excision of the indented regions will be developed to assess elastic/plastic deformation. The oxidation behaviour will be determined using thermogravimetric analysis and microstructural characterisation. In addition, novel binders will be evaluated, with a preliminary screening conducted using sputtering based combinatorial search methods, combined with nano-indentation of the resulting libraries.