Sandvik Coromant unveils new PVD technology

The advantages of PVD tooling grades are well documented – particularly with tough materials, but there’s always room for improvement. In this article, PES discovers how Sandvik Coromant, through its new Zertivo technology, is taking PVD to the next level.

Milling steel in the ISO P materials classification is not without its challenges. Tricky tool paths and thermal fluctuations, in combination with tough or ‘sticky’ materials, means that production engineers have faced a long battle to optimise steel milling operations.

In recent years, PVD (physical vapour deposition) grades have proven a popular choice, but even these can be compromised (depending on application) in terms of crack formation and/or edge line chipping. As a result, Sandvik Coromant has set about reinventing PVD grade technology from the ground up, creating GC1130, a purpose-designed steel milling grade that is the first to take advantage of Zertivo, a new method of production that results in benefits such as longer tool life and enhanced security.

The challenges of milling ISO P materials are well documented. In the first instance, complex toolpaths or difficult to machine materials can cause edge line chipping that leads to poor surface finish and tool failure.

Indeed, milling some of the more ‘tacky’ materials in the ISO P classification can cause flaking of the insert coating, which in turn leads to breakage of the edge line. Furthermore, thermal fluctuations during machining, especially under wet conditions, can cause crack formation, an undesirable effect that tends to induce unpredictable tool life and even sudden breakage. For these reasons, correct insert grade selection is paramount to process security, productivity and profitability.

Thanks to intrinsic properties such as compressive residual stresses, and high hot hardness, PVD grades are a good choice when it comes to milling operations that demand toughness or sharp cutting edges to help overcome sticky materials.

Enhanced ISO P milling

GC1130, the first milling PVD grade produced with Zertivo technology, is optimised for steel milling in all conditions. When developing this advanced new grade, the focus was on solving the issues of chipping, insert flaking and thermal cracks, working with both substrate and coating, to reach longer tool life and secure machining, even in unstable or demanding conditions.

One of the secrets behind the premium performance of GC1130 is its high chromium (Cr) content fine-grained substrate. The inherent characteristics of chromium additions in the cemented carbide help withstand edge-line chipping and cracks arising from difficult machining environments such as temperature and/or load variations, as well as vibrations.

To amplify the important potential advantages of using PVD grades, Sandvik Coromant has devised a new production technology called Zertivo, which takes the whole insert into consideration, not just the coating.

Creating a high quality PVD coating includes many complex process steps; the main ones being pumping, heating, etching, coating and cooling. Besides coating composition, process parameters such as temperature, gas flow and pressure are crucial for final tool performance. After all, variations in the production processes have direct impact on the grade and, ultimately, how the tool performs on the machine.

The Zertivo production technology is designed to take PVD process control to a new level, resulting in improved adhesion between the substrate and the coating, along with optimised cutting edge integrity. Ultimately, the concept behind Zertivo is to ensure that each grade is produced under the right conditions, resulting in a higher quality product for secure machining.

The right balance

When developing Zertivo, Sandvik Coromant focused on creating a platform that would make it possible to offer the perfect balance between various properties to match the requirements of the market. Here, the team deduced that developing a new grade is about optimizing the interplay of several properties, and this is where the company has attained new levels of success with Zertivo.

In effect, the R&D team at Sandvik Coromant has discovered the art of creating the ideal PVD grades, where carefully combined ingredients for both the coating and substrate are merged with precisely controlled process conditions to produce inserts with unbeatable edge line security.

With GC1130, the resistance against chipping has been greatly improved through the introduction of extra predictability and security into the production process. The clean, intact edge of GC1130 promotes high metal removal rates and elevated performance in both wet and dry machining. Furthermore, it is suitable for both roughing and finishing applications.

Ideal for square shoulder end milling cutters, GC1130 is first introduced on the CoroMill 390 with inserts in sizes 07 and 11, although further extensions are planned to follow shortly. In fact, GC1130 will also soon be available in most CoroMill variants. CoroMill 390 is a versatile concept for machining varied component features and materials; the assortment includes many different types of tools and a wide selection of corner radii.

Several customer test sites are already demonstrating the potential gains on offer to discerning production engineers responsible for machine shops where investment and continuous improvement are priorities in a fiercely competitive marketplace.

In a customer example involving slot milling, a subcontractor’s productivity was limited by its standard grade end mill cutter. However, when switching to a CoroMill 390 with size 07 inserts and the GC1130 grade, the increased productivity afforded by a 33% increase in cutting speed from 150 to 200m/minute, and a 50% gain in table feed from 600 to 900mm/minute. Ensured time in cut was reduced from 5.5 to 3.8 minutes and tool life was considerably improved. Moreover, the result was achieved at a 3mm depth of cut, compared with 2mm for the competitor tool.

The future of PVD, today

Production engineers are tasked with continually searching for solutions that help deliver improved performance from milling insert grades. The arrival of GC1130, the first Sandvik Coromant milling grade manufactured using Zertivo technology, signals an opportunity for machine shops to take large strides towards greater process control, productivity and profitability. The result is the ability to compete more effectively for new contracts and build a more robust and successful business.

Sandvik Coromant www.sandvik.coromant.com/uk