Iscar vs Tungaloy Stainless Steel Turning Inserts: Grades, Coatings, and Cutting Performance Compared

Why Stainless Steel Turning Demands Specialized Inserts

Stainless steels (ISO M classification) combine high work-hardening tendency, low thermal conductivity, and strong adhesion to cutting edges. Grades such as 304, 316, and duplex 2205 work-harden rapidly during machining, generating hardened surface layers that accelerate notch wear and edge chipping. The low thermal conductivity of austenitic stainless — roughly 16 W/m·K versus 50 W/m·K for carbon steel — concentrates heat at the cutting zone, demanding inserts with thermally stable coatings and substrates engineered for heat resistance. Both Iscar and Tungaloy have built dedicated grade portfolios and chipbreaker geometries to address these exact challenges. This comparison breaks down the technical differences to help machinists select the right insert for their specific stainless turning application.

Iscar’s Stainless Steel Turning Insert Portfolio

Core Grades and Coating Technologies

Iscar approaches stainless steel turning through a dual strategy of PVD and CVD coated carbide grades, each optimized for different cutting conditions:

• IC5820 — A PVD TiAlN coated grade built on a tough fine-grain substrate. Iscar positions IC5820 as its first-choice grade for austenitic and duplex stainless steels. The PVD TiAlN layer provides a hot hardness exceeding 3000 HV and oxidation stability up to approximately 1000°C, while the substrate’s cobalt-rich binder sustains edge toughness under interrupted cuts.
• IC808 — A PVD coated grade with a multi-layer architecture (TiN/TiCN/TiAlN) engineered for stainless steel and high-temperature alloys. IC808 prioritizes thermal barrier performance, making it suitable for higher cutting speeds where heat management is critical.
• IC28 — A CVD TiCN + Al₂O₃ coated grade for stainless steel and heat-resistant superalloys. The Al₂O₃ outer layer acts as a thermal insulator, reducing heat transfer into the carbide substrate. IC28 is recommended for continuous cutting at elevated speeds.
• IC6025 — A CVD multi-layer grade (MT-CVD TiCN + Al₂O₃) offering broad versatility across steel and stainless applications. Its balanced wear resistance and toughness make it a strong candidate for mixed production environments.

Chipbreaker Geometries

Iscar’s turning chipbreaker program for stainless steel centers on the following geometries:

• MM (Medium Machining) — General-purpose geometry for ap 1.0–4.0 mm and fn 0.15–0.45 mm/rev. The MM geometry produces tight chip control across a wide feed range, critical for austenitic stainless where chip evacuation is difficult.
• MH (Medium-Heavy) — Designed for roughing with ap up to 6 mm. The MH geometry features a stronger cutting edge and wider chipbreaker land to handle higher depths of cut without edge fracture.
• FF (Fine Finishing) — Optimized for low-feed finishing passes at fn 0.05–0.15 mm/rev and ap 0.25–1.0 mm. FF produces excellent surface finish and is effective for minimizing built-up edge (BUE) on stainless.

Iscar also applies its SUMO-TEC post-coating surface treatment to select grades, polishing the coating surface to reduce friction and BUE tendency — particularly valuable when machining gummy austenitic stainless steels.

Tungaloy’s Stainless Steel Turning Insert Portfolio

Core Grades and Coating Technologies

Tungaloy’s stainless steel strategy relies heavily on advanced PVD coatings applied through its proprietary technologies, supplemented by CVD grades for high-speed continuous cutting:

• AH725 — A PVD coated grade and one of Tungaloy’s flagship stainless steel turning grades. AH725 uses a TiAlN-based PVD coating on a wear-resistant substrate, delivering strong resistance to both oxidation and adhesion wear. It is Tungaloy’s first recommendation for austenitic stainless at moderate to high speeds.
• TS2000 — A PVD coated grade specifically developed for stainless steel. TS2000 features a nano-multilayered coating architecture that alternates high-hardness and high-toughness layers, improving thermal shock resistance during interrupted cuts and varying depths.
• SH725 — A newer PVD grade engineered for swarf control and edge security in stainless steel. SH725 targets applications requiring reliable chip breaking across a wide parameter window, particularly in automated turning where unattended chip evacuation is essential.
• AH6235 — A PVD coated grade with enhanced toughness for stainless and alloy steel roughing. AH6235 suits heavier depths of cut and interrupted conditions where edge fracture risk is high.

Chipbreaker Geometries

Tungaloy’s TungTurn chipbreaker program for stainless steel turning includes:

• PS (Precision Slim / Finishing) — For finishing operations at fn 0.05–0.20 mm/rev and ap 0.5–2.0 mm. PS geometry provides a sharp positive cutting edge with a narrow chipbreaker, producing fine chips and superior surface finish.
• PM (Precision Medium) — General-purpose geometry for ap 1.0–4.0 mm and fn 0.10–0.40 mm/rev. PM is Tungaloy’s recommended first-choice geometry for most stainless turning applications.
• PR (Precision Roughing) — Engineered for roughing at ap up to 6 mm and higher feed rates. PR features a reinforced edge and a deep chipbreaker pocket for robust chip control in heavy cuts.

Tungaloy also offers the TungTurn-Jet coolant delivery system on selected holders, directing high-pressure coolant directly to the cutting zone through nozzles integrated into the insert seat — an approach that significantly improves chip breaking and tool life on stainless steel.

Grade and Coating Technical Comparison

Cutting Parameter Comparison — 304/316 Austenitic Stainless

The following parameters apply to turning austenitic 304/316 stainless steel (approx. 180–220 HB) with coolant. Values represent practical operating ranges; actual speeds should be adjusted for machine rigidity, workholding, and specific workpiece condition.

For duplex stainless (2205, ~260 HB), reduce cutting speeds by approximately 20–30% and keep feeds at or above 0.15 mm/rev to avoid work-hardening thin chips. Both Iscar IC5820 and Tungaloy TS2000 handle duplex well, though Iscar’s SUMO-TEC surface treatment gives it a slight edge in BUE suppression on gummy duplex grades.

Chip Control and Surface Finish

Chip control is arguably the most critical factor in productive stainless steel turning. Austenitic stainless produces long, stringy, hot chips that tangle around the workpiece and chuck, posing safety risks and causing downtime. Both manufacturers address this through chipbreaker geometry design:

• Iscar MM geometry produces semi-tight 6/9-shaped chips across a feed range of 0.15–0.40 mm/rev. The geometry’s chipbreaker land is slightly more aggressive than Tungaloy’s PM, giving Iscar an advantage in tighter chip breaking at higher feeds. However, at very low feeds below 0.10 mm/rev, chip control becomes inconsistent.
• Tungaloy PM geometry offers a wider effective chip-breaking window, particularly at lower feeds (0.08–0.10 mm/rev), where it maintains acceptable chip segmentation. This makes Tungaloy preferable for finishing passes and applications requiring a broad stable feed range.
• High-pressure coolant (HPC) significantly extends the chip-control envelope for both brands. At 70–100 bar, both Iscar MM and Tungaloy PM geometries produce short, well-segmented chips even at the lower end of their feed ranges. Tungaloy’s integrated TungTurn-Jet holders give it a packaging advantage in HPC setups.

For surface finish, both FF (Iscar) and PS (Tungaloy) finishing geometries achieve Ra values below 0.8 µm on 304 stainless at fn 0.05–0.10 mm/rev with sharp edges. Tungaloy’s PS geometry, with its sharper positive rake, tends to produce marginally better finish at very low feeds, while Iscar’s FF offers longer tool life at equivalent parameters due to its slightly more robust edge.

Tool Life and Wear Mechanisms

Stainless steel turning predominantly produces three wear modes: notch wear at the depth-of-cut line (caused by work-hardened layer), crater wear (from chemical dissolution of the coating at high temperatures), and adhesion/BUE (workpiece material welding to the edge). The two brands’ grades respond differently:

• Iscar IC5820 excels in notch-wear resistance thanks to its tough substrate and SUMO-TEC polished surface, which reduces adhesion. In continuous cutting of 316 stainless at Vc 180 m/min, IC5820 typically delivers 15–25 minutes of cutting time before the 0.3 mm flank wear criterion is reached.
• Tungaloy TS2000 shows superior thermal shock resistance in interrupted cuts, where its nano-multilayer coating architecture slows crack propagation. In interrupted turning of 304 stainless at Vc 170 m/min, TS2000 can extend tool life by 10–20% over IC5820 under identical conditions.
• Iscar IC808 and Tungaloy AH725 both target high-temperature stability. IC808’s thicker multi-layer PVD coating provides excellent crater-wear resistance at speeds above 200 m/min, while AH725 balances adhesion and crater resistance effectively in the 160–200 m/min range.

Application-Based Selection Recommendations

Summary

Iscar and Tungaloy take technically distinct but equally valid approaches to stainless steel turning. Iscar’s IC5820 with SUMO-TEC stands out for continuous high-speed cutting and duplex applications where BUE suppression is paramount, while Tungaloy’s TS2000 and SH725 shine in interrupted cuts and automated environments demanding broad chip-control stability. For finishing, Tungaloy’s PS geometry offers a sharper edge and wider feed window, whereas Iscar’s FF provides longer life at equivalent parameters. The optimal choice ultimately depends on the specific stainless grade, cut type (continuous vs. interrupted), chip-control requirements, and coolant strategy. In most production environments, maintaining inserts from both portfolios allows machinists to match the insert to the operation rather than compromising on a single brand’s strengths.