ICMCTF 2025 Session IA3-TuA: Innovative Surface Engineering for Advanced Cutting and Forming Tool Applications

The manufacturing process of traditional cutting materials such as cemented carbide involves significant energy consumption and costly raw materials that are often linked to environmental harm during extraction. To address these concerns, there is a growing demand for developing sustainable cutting materials. In this context, natural materials are both environmentally friendly and abundant. Natural rocks, in particular, are promising due to their hardness, which typically ranges from 8 to 16 GPa depending on the rock type. The suitability of these natural materials for machining can be enhanced via functionalization of the surface properties by applying a protective thin film using physical vapor deposition (PVD) technology.

Preliminary studies show the suitability of various rock types as cutting material. Cutting inserts are crafted from these natural rocks and subsequently ground. A TiN thin film is deposited onto the various natural rock inserts using a magnetron sputtering process. The resulting TiN thin films crystallize in a cubic structure on all rock types. The obtained hardness values are comparable to TiN thin films grown on tool steel. In contrast to a polished surface, a ground surface of the natural rocks promotes good adhesion of the TiN thin films. To assess the cutting performance and wear characteristics of PVD-coated natural rocks, turning tests are conducted using the aluminum alloy Al7075. The TiN thin film significantly enhances wear resistance, thus extending the service life of the cutting inserts. Additionally, it is observed that the distinct material properties of the natural rocks significantly affect the wear behavior. Rock types with a more homogeneous structure demonstrate improved wear resistance over extended cutting lengths.

To analyze the effect of the substrate on the TiN thin film adhesion three different glass substrates were chosen as surrogates for natural rocks. Glasses are particularly suitable as surrogates because of their similar SiO2 content. The investigations reveal a strong influence of the stress state on the adhesion, as TiN on window glass shows weaker adhesion due to high compressive residual stresses. The possible adaptation of thin film design strategies developed for glass onto natural rock surfaces is evaluated. The utilization of a PVD-coated natural rock emerges as a promising concept for broadening the spectrum of cutting materials and promoting sustainability in their manufacturing. A tailored adjustment of the grinding process for cutting inserts with an adapted thin film design is anticipated to further elevate the cutting performance of natural rock inserts.

In the plastic processing industry, molds and tooling components are frequently exposed to chemically aggressive environments, particularly when handling plastics containing halogenated and phosphorus-based flame retardants. While CrN coatings generally offer good corrosion resistance, their wear resistance may fall short when processing plastic formulations containing highly abrasive additives such as glass fibers or hard polymers like polycarbonate. In addition, achieving an ultra-smooth surface finish is essential for producing mirror-polished plastic components, requiring deposition techniques that enhance surface quality while ensuring precise control over coating thickness to meet stringent dimensional tolerances.

To address these challenges, we developed Si-alloyed CrN coatings using Oerlikon Balzers' Scalable Pulsed Power Plasma (S3p) technology. Si-doped Cr targets with varying Si concentrations were employed to systematically investigate the effect of Si content on the microstructure and mechanical properties of the coatings.

Utilization of coating and surface texturing techniques combines to great effect to further enhance the overall performance of carbide surfaces. For these materials, adhesion is most critical in defining the performance of the coating. Poor adhesion and coating quality can lead to eventual failure. With cemented carbide being one of the materials of concern, LST has gained much attention as having superior mean coating adhesion. However, the effects of the combined processes of coating followed by texturing and texturing followed by coating and their interactions remain poorly understood.

This study analyzes micro-structured coated cemented carbide surfaces prepared from varying processes and property conditions while examining their surface characteristics and friction performance. The performance of the substrates, which had undergone surface treatments followed by ball-on-disk tests, was then evaluated and compared. The coated surface sample, where surface texturing was done first and coating applied afterward (AC), showed better microhardness, more refined microstructures, and better wear resistance than the coating surface first, followed by surface texturing (BC). Although the sample coated was found to show superior hardness values across the board, the AC sample displayed more favourable results in other areas. A prime example is that the AC sample was 12% more microhard than the coating sample, although the overall hardness was reduced by 3%, coupled with a reduction in friction force by 8%.

It creates an insightful mark to realize that the order of application of the texturing and coating processes would bear significant relevance in affecting the final performance of the material. This study now stresses that enhanced adhesion and wear resistance were found in the coating substrate wherein the texturing technique was performed first and then coated (AC) as being very consistent in proposing that these combined techniques can make way into producing contributions toward more durable and effective coatings for industrial usages.

Cyclic loading is critical for the industrial application of PVD coatings, especially in metal forming applications. With the increasing interest in using thin super-high-strength steel sheets for forming bodies/parts with reduced component weight, light-weight design and less fuel consumption could be achieved for example in automotive industry. Consequently, the loads become more demanding on molding dies and therewith protective coatings. These applications require coatings resistant to cyclic mechanical and/or thermal loading and fatigue. The specific structure of voestalpine eifeler’s Duplex-VARIANTIC ^® -1400-plus with its multiple hard material AlXN layers overcomes the very demanding requirements in terms of strength, hot-hardness, and load-bearing capacity in such metal forming applications and outperforms other commercially used hard nitride protective coatings. This property profile makes voestalpine eifeler’s Duplex-VARIANTIC^®-1400-plus the optimal solution for metal forming high-strength and advanced high-strength steel sheets.

Cathodic arc evaporated (CAE) coatings are dominating the field of wear resistant PVD thin films for tools due to their excellent adhesion, high deposition rates and outstanding performance as well as service life in industrial scale applications. An established approach to control the movement of the arc spot on the cathode surface during the deposition process is the use of static magnetic fields, which are generated by a defined arrangement of permanent magnets placed close to the cathode material. However, this solution is strongly limited in its setting options and does not consider any dynamic effects such as an increasing magnetic field strength caused by changes of the erosion profile of the cathode material or adjusted evaporator currents. To overcome these challenges and limitations of CAE processes electro-magnetic fields generated by coil systems (CS) are a promising approach to precisely control and adjust the magnetic field design and strength and therefore enable the possibility of tailored and improved properties of PVD coatings. Due to this reason, a coil system consisting of an inner and outer independently controllable coil, which additionally allows switching of the polarity was used for an industrial scale arc source (APA evaporator) as well as in combination with permanent magnets. It was found, that besides the higher material utilization compared to permanent magnetic setups for cathodic arc materials, the adjustment of the magnetic field by APA CS enables the possibility of maintaining the desired fcc-structure for high Al-contents in Al-rich AlTiN coatings. Additionally, this dedicated setup can be used for challenging CAE processes for “hard to evaporate materials” in combination with a dynamically controlled magnetic field for steering the arc spot. A homogenous erosion profile of the cathode material was achieved for the deposition of carbon coatings with adjustable hardness profile.

Materials in the nanoscale range are used as diagnostic instruments or to deliver therapeutic compounds to specific targeted regions in a controlled manner in nanomedicine and nano delivery systems, which is a relatively young but fast emerging discipline. By delivering precise medications to specified locations and targets, nanotechnology provides numerous advantages in the treatment of chronic human diseases. The medication-related toxicity is reduced by this focused and prolonged drug delivery, and patient compliance with less frequent dosage is improved. Nanotechnology has been successful in treating diseases including cancer, AIDS, and many others. It has also advanced diagnostic testing. High stability, high carrier capacity, the ability to incorporate both hydrophilic and hydrophobic molecules, and the ability to administer drugs via a variety of routes, including oral application and inhalation, are key technological benefits of nanoparticles used as drug carriers. Nanotechnology is being implemented in the field of infection treatment due to the rise of drug-resistant bacterial types, where it is being used for drug delivery purposes. Because nanostructures can be used as delivery agents to enclose medications or bind therapeutic substances and deliver them to target tissues more accurately with a controlled release, nanomedicines have gained popularity recently. A developing subject called nanomedicine applies nanoscience knowledge and methods to medical biology, disease prevention, and treatment. It suggests the use of nano dimensional materials such as nanorobots, nano sensors for delivery, diagnosis, and sensory functions, as well as actuating materials in living cells. In this keynote talk, I will focus on our recent research works on nano carrier drug delivery systems and the future prospects.