Surface World May 2018 Surface World May 2018 - Page 15

During the initial six months of this 12 month ‘feasibility study’, the majority of the work has been undertaken at SHU using their production scale Hauzer TechnoCoating 1000/4 High Power Impulse Magnetron Sputtering (HIPIMS) coating equipment together with their suite of advanced optical emission spectroscopy and plasma diagnostics facilities and has: single analytical technique – OES – to monitor and control all stages of PVD processes and provide real-time automatic control and assurance of coating adhesion, coating thickness and coating composition as well as real-time condition monitoring of the coating system. This will enable optimization of product quality and system productivity whilst eliminating product rework. Importantly, this approach will provide an additional level of tracibility for the production cycle of parts. Digital data will be available for each step in real time. It will describe the product and could be used to predict its likely performance and even lifetime after deployment. Meeting this requirement will make PVD ready for Industry 4.0. It will enable the technology to be part of the supply chain and increase the flexibility in materials design for high value manufactured products. OES has been in use for a number of years to optimise deposition conditions in reactive sputter processes by maintaining the relative intensity of selected emission lines from the magnetron sources by controlled admission of the reactive gas(es). Such systems typically use a simple diffraction grating spectrometer in which the output of a photodetector controls the operation of a piezo-electric valve via a feedback loop to keep the relative intensity of a particular emission constant. More recently systems have been developed that can monitor and control multiple sources and/or multiple locations on individual sources. However, such systems are invariably used only during the deposition phase of the process and then only to maintain the relative state of the magnetron discharge in the presence of reactive gas flow compared to the discharge in the absence of that flow. The innovation in this study is to evaluate the feasibility of stretching the capabilities of optical emission spectrometry and applying it to a wider scope of tasks by providing real-time control of all active phases of the deposition process – evacuation, substrate cleaning, coating deposition – as well as providing real-time condition monitoring of the coating system itself. The main commercial innovation will be in developing a new means of controlling a PVD process which will result in a significant improvement to coating reproducibility. This will be the first time a strategy will combine the monitoring of all steps of the coating process. We aim to improve coating thickness reproducibility from the current ±25% to <±5%. If successful, the development will break the barriers to coating exploitation within the automotive and aerospace component sectors paving the way to increasing the current (minimal) market penetration, of c10%, of an additional market worth in excess of £75M. It has the potential to drive innovations in a number of sectors where PVD coatings could be applied for the first time such as safety critical parts of airframes and aeroengines. 1. demonstrated the viability of using the integrated intensity of emission lines from the metallic sources to monitor coating thickness; 2. demonstrated the use of OES for controlling coating crystallographic texture by controlling the ratio of optical emissions from metallic and non-metallic species; 3. identified suitable emission lines for monitoring the progress of system pump- down and signalling when it is ready to move to the next stage of the process; 4. developed procedures for monitoring the progress of the in-chamber cleaning (plasma etching) process and signalling the end point for this. During the remaining six months the emphasis will move to Ionbond’s Consett, Co Durham facility where the procedures and results obtained so far will be rigorously evaluated using full-scale production cycles on its brand new Hauzer Techno Coating Flexicoat 1500 large UBM sputter coating machine, and which will provide data for the development of optimised preventative maintenance condition monitoring procedures. The authors acknowledge the support of Innovate UK under their programme of Technical Feasibility Studies for Surface Engineering and Coating Technologies for High-Value Manufacturing, project number 132890 ‘ Real-time monitoring and control of magnetron sputter deposition of thin coatings’. 13