What is Surface Engineering?
Why are Surfaces Important?
An engineering component usually fails when its surface cannot adequately withstand the external forces or environment to which it is subjected. The choice of a surface material with the appropriate thermal, optical, magnetic and electrical properties and sufficient resistance to wear, corrosion and degradation, is crucial to its functionality. Sometimes technological progress and manufacturing efficiency may be constrained solely by surface requirements. For example, the fuel efficiency and power output of gas turbines or diesel engines are limited by the ability of key components to withstand high temperatures. However, it is often impractical, inefficient or uneconomical to manufacture components from a bulk material simply for its surface properties - far better to use a cheaper, more easily formed underlying material and coat it with a suitable high performance film. The resulting product conserves scarce material resources, performs better than the original and may well be cheaper to produce.
Improving the functionality of an existing product is only one aim of surface engineering. New coatings and treatment processes may also create opportunities for new products which could not otherwise exist. For example, satellites could not function, nor could modern power plants operate safely, without the application of advanced surface engineering techniques.
The economic benefits of surface engineering are enormous. According to a report by RCSE staff, in 2005 the value of the UK coating market is approximately £21.3 billion, and those coatings critically affect products with a value greater than £143 billion (Source: "2005 Revisited; The UK Surface Engineering Industry to 2010", A Matthews, R Artley and P Holiday).
In brief, surface engineering is relevant to all types of products. It can increase performance, reduce costs and control surface properties independently of the substrate, offering enormous potential for:
- improved functionality
- the solution to previously insurmountable engineering problems
- the possibility to create entirely new products
- conservation of scarce material resources
- reduction of power consumption and effluent output
Scientific Research and Industrial Relevance
The need for concentrated research into surface engineering has never been greater. Practice is currently running ahead of basic scientific understanding in some fields, with the result that consistency and quality are suffering. Further exploitation of the technology depends on new pure and applied research to underpin developments.
Surface engineering embraces a wide range of techniques, but it is the Plasma & Ion-based Surface Engineering (PISE) techniques which are attracting the greatest international interest, and it is in this field that the RCSE has particular expertise. PISE techniques offer the most promising methods of improving surface quality to better control the structure and increase the reliability and reproducibility of coatings by precise process control. This is crucial, for example, in providing properties to withstand complex loading conditions in corrosive environments.
The PISE techniques have several important advantages:
- large surfaces are easily treatable
- PISE is based on dry technology, avoiding the use of harmful solutions
- unlike traditional techniques, the processes are virtually pollution free
- such processes can be easily automated
- properties such as corrosion and wear resistance, fatigue strength and biocompatibility, as well as the combination of these properties, are achievable and controllable.
Although PISE methods are potentially among the most useful surface engineering techniques, the RCSE is also researching into more traditional processes and other emerging technologies such as plasma electrolysis.
Examples of research areas currently covered are:
- Fundamental studies of plasma and ion-based vacuum deposition systems. This work has basic science and applied technology dimensions and will lead to process optimisation and improved monitoring and control. A feature of the research is the investigation of process up-scaling, studying the problems inherent in moving from laboratory equipment to larger scale systems.
- The development of high temperature diffusion and corrosion-resistant coatings. This work also has important implications for fibre reinforced metal matrix composites, used or produced at elevated temperatures, where fibre coating is now a key issue. The development of thermal barrier coatings which will improve fuel efficiency and specific power output of gas turbines is a further aspect of this research.
- Research on advanced electroless deposition. This involves more traditional technologies which will have an important and developing role, e.g. for the production of alloy coatings for use in the electronics industry. The work also includes the investigation of duplex coatings, combining electroless and reinforced electroless coatings with PVD, for example.
In addition, the RCSE is researching related topics such as advanced 'duplex' processes which involve the application of DC or RF plasma (usually of nitrogen) to produce load-supporting surface layers, which are then coated with hard PVD layers (such as new Ti-Al-Si-B-N compounds). These processes show particular promise when applied to low alloy steels, stainless steels, or the light alloys.
Other topics for research include the continued development of PVD equipment design, processes for the deposition of diamond and diamond-like coatings and computer expert systems to assist design engineers.