High performance protective coatings on the inner diameter of landing gear components for the replacement of hard chrome: assessment and predictive modeling of fatigue behavior

重型部件通常被镀上一层硬铬，称为电解硬铬，以提高部件的性能。从健康和环境的角度来看，使用六价铬生产这种电镀是不安全的，不断增加的监管要求推动了替代工艺和合金的发展。另一种选择是采用高速氧燃料(HVOF)热喷涂的碳化钨涂层。它们越来越多地取代了起落架、直升机动力部件、螺旋桨轮毂和液压执行器上的电解硬铬电镀。这些喷涂涂层往往比电解硬铬涂层提供更好的磨损、腐蚀和疲劳性能，为涂层涂覆者和航空航天制造商带来直接的成本效益。然而，这项技术不能很容易地转化为受限的内表面或难以触及复杂形状的区域，例如较小的内径。这项提议和合作的目的是促进内径(ID)超音速火焰喷涂硬质合金涂层的技术成熟度。作为一项更广泛倡议的一部分，目前的目标是将ID-HVOF的加工范围定义为所需粉末原料和涂层性能的函数，预测其微观结构，表征和描述涂层/基材组件的疲劳行为和使用中的行为。将使用数据分析工具来提高过程的稳健性。该研究项目的潜在成果包括一种新的高附加值涂层技术，用于深孔零件和难以接触的表面，一种了解和预测此类零件在使用中性能的方法，以及符合行业4.0预期的过程控制策略。该项目的成果将有利于包括材料供应商、设备供应商、涂层涂覆商和原始设备制造商在内的整个价值链的加拿大公司生产性能更高的部件，减少制造业务对环境的影响，并成为具有全球影响的阶段性变革技术的一部分。

Heavy duty components are often plated with a hard layer of chrome, called electrolytic hard chrome, to improve the part performance. Producing such plating through the use of hexavalent chrome is not safe from a health and environmental point of view and the ever increasing regulatory requirements push the development of alternative process and alloys. An alternative is a tungsten-carbide coating applied by High Velocity Oxy-Fuel (HVOF) thermal spraying. They have increasingly replaced electrolytic hard chrome plating on landing gears, helicopter dynamic components, propeller hubs, and hydraulic actuators. Those sprayed coatings tend to provide superior wear, corrosion and fatigue performance than electrolytic hard chrome plating, yielding direct cost benefits for both the coating applicator and the aerospace manufacturer. However, the technology cannot be readily translated to confined internal surfaces or difficult to reach areas of complex shapes, such as the smaller internal diameters. The aim of this proposal and partnership is to advance the technological maturity of inner-diameter (ID) HVOF carbide coatings. As part of a wider initiative, the present objectives are to define the processing domain of ID-HVOF as a function of the required powder feedstocks and coating properties, predict their microstructure, characterize and describe the fatigue behaviour of the coating/substrate assemblies and in-service behaviour. Data-analytic tools will be used to increase the process robustness. The potential outcomes of this research project include a new high value-added coating technology for deep bore parts and difficult to reach surfaces, a methodology to understand and predict in-service performance for such parts and a process control strategy meeting Industry 4.0 expectations. The outcomes of this project will benefit Canadian companies encompassing the entire value chain of material suppliers, equipment providers, coating applicators and original equipment manufacturers in producing higher performing components, reducing the environmental impact of the manufacturing operations, and being part of a step-change technology of global impact.