Cermet tooling, as the name suggests, is a hybrid of ceramic and metal tools. These tools, made of ceramic particles linked together with a nickel binder, may run faster than cutting carbide tools and are significantly more wear-resistant. In addition, these inserts have an extremely flat surface, which allows the chip to flow freely and prevents built-up edges.
Traditionally, ceramic tooling has been utilized for high-temperature cutting, particularly in hard materials. These tools, however, are incredibly fragile and can only tolerate minor interrupted cutting. In addition, because it is not an actual ceramic insert, the qualities of the carbide reamers allow cermets to bend somewhat when mixed with metal.
“The nickel binder of solid carbide reamers can withstand the heat generated during the cutting process better than the cobalt binder.” “Heat is the enemy in every cutting application,” said Steve Geisel, Senior Product Manager at Iscar Canada.
Cermets were created for high-quality surface finishes, cutting at high spindle speeds (800 to 1,200 SFM) and cutting continuously for lengthy periods. “While carbide tooling can now run at 1,000 SFM due to improved coatings and substrates,” Geisel explained, “it still cannot match with cermet tooling in terms of surface polish.” “Using a cermet insert produces less friction than a carbide insert, which results in less vibration.”
The greater the friction, the more difficult it is to maintain a high-quality surface polish. According to Geisel, the only option to achieve surface finishes similar to those produced by cermet tooling is to use a carbide insert with a wiper system.
Technology of Coatings
Iscar’s cermets are PVD-coated and laminated, often with titanium nitride (TiN), titanium carbonatites (TiCN), and titanium carbide (TiC). Cermet tooling is usually crisp, which is why it is PVD-coated rather than chemical vapor deposition- (CVD-) coated.
“Coatings can extend tool life,” Geisel stated. “Coated ceramics will undoubtedly live longer, which helps minimize consumable costs.”
Tool life is also easier to anticipate with cermet tooling than carbide reamers since the tool is constantly engaged in the cut.
Cermet tooling is ideal for cutting carbon and alloy steels to tight tolerances, but it can also cut stainless steels and high-temperature alloys. However, it should not be used to cut cast iron or aluminum.
Use of A Coolant
When cutting using cermet equipment, a flood coolant arrangement is advised.
“The coolant lubricates the incision while also cooling the chip,” Geisel explained. “More heat is created in the end due to the high cutting speeds obtained.” Coolant keeps the region cold and offers an environment conducive to effective chip management.”
Chip control is critical at this step since the last thing you want to do at the finish stage is damage the work piece’s surface. In addition, the item may have previously been machined for several hours. “Despite the improvement in carbide tooling, people have not forgotten about cermets,” Geisel remarked. “While carbides have made tremendous gains in recent years, cermets are evolving, with novel chip formers and geometries available.”
Technical Advances
Although cermet and ceramic cutting tools have a long history, toolmakers continue to innovate. According to Wilshire, one such development at Kyocera is creating a gradient in cermet material using various methods used throughout the insert pressing and sintering processes. “Those are referred to as ‘hybrid cermets,’ since they have a hard outer layer and additional toughness in the middle.”
In ceramic inserts, Kyocera also mixes tough. Wilshire noted that the business could create a honeycomb-shaped grain structure in which the hexagon shape of the honeycomb is built of a tougher ceramic than the more complex inner core it surrounds. If the central component cracks, it will not spread beyond the shell and cause the insert to shatter.
“It competes with the substance for whiskers,” he explained.
Kyocera does not manufacture whisker-reinforced ceramic inserts, but according to Wilshire, the company does provide a second approach to increase the fracture resistance of ceramics similar to those reinforced with SiC crystals. The grain structure of the company’s newer SiAlON materials is adjusted to induce some grains to become needle-shaped, identical to whiskers. “The crystals develop throughout the sintering process,” he explained. Hard particles are also included in the structure for wear resistance. Furthermore, according to Howard, it is critical that end users understand the best practices for machining with ceramics to gain the greatest performance from the insert. This involves ramping cuts, altering the DOC, and lowering the feed towards a corner.
