Surface engineering is concerned with the modification of a surface to provide advantages in terms of functionality and performance. Surfaces can be engineered by many different processes including adding a coating to the surface by physical or chemical deposition, or by modifying the surface by physical or chemical processes. Surface engineering is used throughout manufacturing and engineering industries to enhance the surface of components that can then be made from low-cost, lightweight materials.
Examples of characteristics optimised through surface engineering:
• Wear resistance
• Corrosion resistance
• Thermal insulation
• Oxidation resistance
• Chemical diffusion barrier
• Friction reduction
• Fatigue strength
• Electrical resistance
• Electrical Conductance
• Non-stick
• Anti-microbial
• Biocompatibility
There are many characteristics of components that can be optimised through surface engineering, see list above. These bring tremendous benefits to industry and society and have the potential to make a major contribution to the goals of achieving a net zero economy and sustainable use of materials through reductions in friction, increasing the durability of products, and enabling improved more cost and energy-effective design of products. One example of the use of surface engineering is through surface treatment or the application of advanced coatings to increase the lifetime of components subjected to extreme environments. These extreme environments include corrosion from liquids or chemical reactions (e.g. bridges) or oxidation at high temperatures (e.g. furnace components), or severe mechanical loading (e.g. machinery) where reductions in friction, increases in the wear resistance, and increases in the surface strength and resistance to fatigue damage are all possible with the correct choice of surface engineering process (see characteristics listed in red in list). In many cases, the lifetime of the component can be increased indefinitely.
As performance and lifetime requirements steadily increase, new advanced coatings to address these issues are continually being developed. During the development of any new coating, it is important for any new materials to be characterised to assess that they will be fit for purpose. It is too slow and expensive to take a blind application-specific empirical approach to development. Optimising the processing and surface engineering of components also requires continual measurement to ensure that the final components meet the requirements of a design for manufacture (DFM) culture,
Indeed, it is extremely useful when any coated system is optimised to have reliable data to feed into the development process. This is particularly true when the requirements of Industry 4.0 and digitalisation of design and manufacture where assured materials data on properties and performance are essential.
National Physical Laboratory (NPL) is concerned with the development of techniques for the evaluation of material properties and performance and the ability to characterise these aspects over appropriate length scales. This is an underpinning requirement for all industrial sectors and requires a higher degree of assured data to support and develop smarter digital ways of working and designing with advanced materials.
The development of new processing routes and new coating systems for surface engineering is rapidly developing and is accelerating faster than the necessary provision of standards and regulations. Projecting forward it is extremely likely that industry will need help to provide assurance that current test methodologies and standards are appropriate and fit for purpose. There is likely to be a need for hybrid testing based on current best practice and recognised test methods but modified to take advantage of modern sensors and measurement techniques to provide reliable and impartial measurement solutions. The industry will need reliable data for modelling, reliable methods to extract the properties that models need from measurement data, and in-service performance predictions to enable safe and economic asset maintenance. Greater emphasis will be placed on multi-modal testing to deliver data-rich measurements to enable rapid testing and accelerate the uptake of advanced materials.
As material performance increases even the smallest improvements in properties are becoming increasingly important to accurately measure and characterise. Marginal gains can result in major gains in performance lifetimes. This results in more sustainable engineering systems with lower waste and a resultant reduced impact on the environment. In an age of many environmental concerns, these improvements are critical to meeting Governmental and International targets. Reliable, accurate measurements with the necessary resolution are increasingly important to validate and aid in the development of these degradation-resistant surfaces. This requires data to be readily available and accessible so that purported claims and analyses can be checked and verified. Having data with the appropriate digital thread and metadata to support this is vital and is a key aim of NPL in its current and future programmes of work.
NPL recently carried out an exercise to identify the measurement areas that were of most concern to the industry. The current focus of NPL work addresses the major concerns identified in the development of the assurance and validation of methods for the assessment of coating adhesion, wear resistance and mechanical strength. These properties all have a major impact on the durability of engineered surfaces subjected to extreme environments.
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