Climate change, because of greenhouse gas (GHG) emissions from human activities, has become a critical issue as it is affecting our environment. According to the Paris Agreement, an international agreement on reducing GHG emissions and addressing climate change, it was agreed that global warming should be kept below 2°C above the preindustrial level and preferably at 1.5°C. To be able to reach this goal, countries and non-state entities, such as companies and individuals, are making efforts to reduce GHG emissions. In this respect, as with many other companies, Seco Tools AB has a goal to reduce 50% of its GHG emissions by 2030 and reach net zero emissions by 2050.

This study was conducted with the aim of determining and understanding the impact of GHG emissions in physical vapor deposition (PVD) coating production. In addition, to potentially increase the use of materials and reduce GHG emissions, a study was done on the effect of recycling cathode (target) materials on the process, microstructure, and properties of TiAlN coating. The analysis was performed to determine how much CO2 emissions can be avoided by recycling cathode materials.

The boundaries selected for the estimation of GHG emissions are the use of electrical energy, water, process gases, and cathode materials during the process. The present study shows that the PVD coating process emits about 13.76 kg CO2 to produce a standard batch of TiAlN coating. The shares of emissions from cathode materials, electrical energy, water, and process gases are 76%, 17%, 6%, and 1%, respectively.

The effect of recycled materials on the process, microstructure, and properties of TiAlN coatings produced by cathodic arc deposition was investigated. The coatings were grown with varying chemical compositions from recycled cathodes on cemented carbide substrates at different substrate bias voltages (-25 V, -45 V, and -65 V). The coating thickness, adhesion strength, microstructure, macroparticle presence, phase formation, and residual stress of coatings were investigated and compared with those produced with virgin cathodes, and the results were found to be similar. The coatings showed excellent adhesion strength, and the thicknesses ranged from 1.9 to 3.2µm. The cross-sectional micrographs revealed that the coatings exhibit dense columnar microstructures and the presence of microparticles. Applying a higher bias voltage resulted in coatings with fewer microparticles and increased compressive residual stresses. Phase analysis by X-ray diffraction indicated that a single cubic phase was formed in the coatings. 

The analysis of the impact of cathode recycling on GHG emissions reduction revealed that a proper recycling procedure can potentially reduce 9.70 kgCO2 per batch.