Tungaloy and the TAC Legacy
Tungaloy Corporation, headquartered in Fukushima, Japan, has been developing cemented carbide cutting tools since 1929 under the TAC brand name. The TAC (Tungsten Alloy Carbide) designation has become synonymous with high-performance indexable inserts used across automotive, aerospace, and general machining industries. Today, Tungaloy operates as a member of the IMC Group alongside Iscar, providing a product portfolio that spans turning, milling, drilling, and grooving applications.
Understanding Tungaloy’s Coating Architecture
Modern Tungaloy inserts employ multi-layer coating systems deposited via chemical vapor deposition (CVD) or physical vapor deposition (PVD) processes. The coating architecture typically consists of three functional layers applied over a graded carbide substrate:
- Adhesion layer: A thin titanium nitride (TiN) or titanium carbonitride (TiCN) layer deposited directly onto the substrate to promote bonding between the carbide and subsequent coating layers.
- Wear-resistant layer: The primary functional coating, usually aluminum oxide (Al2O3) for CVD grades or titanium aluminum nitride (TiAlN) for PVD grades. This layer provides resistance against abrasive and diffusion wear at the elevated temperatures generated during high-speed machining.
- Top layer: A titanium nitride (TiN) or chromium nitride (CrN) identification layer that provides a gold-colored surface, reduces friction, and allows visual wear monitoring.
T-Series CVD Grades
The T-series designates Tungaloy’s CVD-coated grades, optimized for high-speed continuous turning of steel and cast iron at elevated cutting speeds.
T9115 — Steel Turning Premium Grade
T9115 represents Tungaloy’s flagship CVD grade for steel turning. It features a thick aluminum oxide (Al2O3) outer layer deposited through a medium-temperature CVD (MTCVD) process, which produces a fine-grained, crack-free alumina coating approximately 10-15 micrometers thick. The MTCVD process operates at lower temperatures than conventional CVD, resulting in smoother coating surfaces with fewer micro-cracks that could propagate under thermal cycling.
The substrate beneath the T9115 coating uses a tough, cobalt-enriched zone near the surface that absorbs impact energy during interrupted cuts. This substrate-coating combination allows T9115 to operate at cutting speeds of 200-350 m/min on carbon steel (C45/1045), with feed rates up to 0.4 mm/rev in semi-finishing applications.
T9125 — Universal Steel Grade
T9125 fills the general-purpose role in Tungaloy’s T-series, offering a wider application window than T9115 at a slight cost to peak performance. The coating system uses a combination of TiCN and Al2O3 layers with a moderate total thickness of 12-18 micrometers. T9125 is specified when the same insert must handle both roughing and semi-finishing operations on a CNC lathe, reducing tool change time and inventory requirements.
T9135 — Heavy Interrupted Cutting
T9135 features Tungaloy’s thickest coating (approximately 20-25 micrometers) with an emphasis on fracture resistance. The coating incorporates a specialized stress-relief layer between the TiCN and Al2O3 that prevents delamination under heavy impact loads. This grade targets gear blank machining, forged component roughing, and other applications where the cutting edge repeatedly enters and exits the workpiece.
AH-Series PVD Grades
The AH-series represents Tungaloy’s PVD-coated product family, designed for applications requiring sharper cutting edges and lower cutting forces than CVD grades can provide.
AH725 — Stainless Steel Specialist
AH725 uses a multi-layer TiAlN PVD coating deposited at temperatures below 500 degrees Celsius. The low deposition temperature preserves the sharpness of the insert’s cutting edge, which is critical when machining work-hardening materials like austenitic stainless steels (304, 316L) and nickel-based superalloys. The TiAlN coating forms a protective aluminum oxide film at cutting temperatures above 600 degrees Celsius, providing self-healing wear resistance during continuous machining.
For austenitic stainless steel turning, AH725 performs optimally at cutting speeds of 120-200 m/min with feeds of 0.1-0.25 mm/rev. The PVD coating’s low friction coefficient reduces built-up edge formation, a common problem when machining gummy stainless materials.
AH8015 — High-Speed Finishing
AH8015 is Tungaloy’s high-speed PVD grade for finishing operations on hardened steels and heat-resistant alloys. This grade uses an aluminum-rich TiAlSiN nanocomposite coating that maintains hardness above 800 degrees Celsius. The silicon content in the coating creates a nanostructured film with grain boundaries that impede crack propagation, allowing the insert to withstand the high thermal loads generated at cutting speeds above 300 m/min.
AH8005 — Hard Turning Grade
AH8005 targets PVD-coated hard turning applications on materials in the 45-65 HRC range. The coating uses a thick TiAlN/TiSiN multilayer structure with approximately 5,000 individual nanolayers, each only a few nanometers thick. This superlattice structure provides exceptional hardness (above 3,500 HV) while maintaining enough flexibility to absorb the cyclic loading inherent in hard turning.
Tungaloy’s Premium Coating Technologies
TAC Coating — Nano-Tech
Tungaloy’s proprietary Nano-Tech coating technology deposits alternating nanolayers of TiAlN and CrN at the atomic level, creating a superlattice coating with hardness exceeding 3,800 HV. The nanostructure also provides excellent lubricity, with friction coefficients as low as 0.3 against steel at elevated temperatures. This technology is featured on select AH-series grades for stainless steel and titanium alloy machining.
Premium Smooth Coating (PSC)
Tungaloy’s PSC process applies a post-coating surface treatment that removes micro-droplets and surface roughness from the CVD coating. The resulting ultra-smooth surface reduces chip adhesion and friction, improving surface finish on the workpiece by up to 30% compared to standard CVD-coated inserts. PSC-treated grades are designated with an “S” suffix in the grade numbering system.
Grade Selection Framework
When selecting between T-series and AH-series grades, consider these decision factors:
- Cutting speed above 200 m/min on steel: Choose T-series CVD grades (T9115 or T9125) for their superior heat resistance.
- Cutting speed below 200 m/min on stainless or exotic materials: Choose AH-series PVD grades (AH725 or AH8015) for sharper edges and lower cutting forces.
- Interrupted cuts on steel: T9135 for severe interruptions, T9125 for moderate interruptions.
- Hard turning (above 45 HRC): AH8005 for finish operations, or transition to CBN inserts for heavy roughing.
- Cast iron machining: T-series grades with silicon nitride-based ceramic coatings provide excellent crater wear resistance at high speeds.
Competitive Positioning
Tungaloy’s TAC coating technology competes directly with Sandvik’s Inveio coating, Kennametal’s Beyond Blast, and Mitsubishi’s VP15TF. The T-series CVD grades offer comparable performance to Sandvik’s GC4225/GC4235 grades at typically 15-25% lower price points, making Tungaloy a strong value proposition for cost-conscious production environments. The AH-series PVD grades compete favorably with Iscar’s IC908 and Sandvik’s GC1125 in stainless steel and superalloy applications.
Conclusion
Tungaloy’s dual-platform approach — T-series CVD for high-speed steel and cast iron, AH-series PVD for stainless and exotic materials — provides a clear and logical framework for insert grade selection. Understanding the coating architecture behind each grade enables machinists to make informed decisions that optimize tool life, surface quality, and production throughput. With the Nano-Tech and PSC technologies, Tungaloy continues to push the boundaries of coated carbide performance while maintaining competitive pricing across its product range.
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