Sandvik codes a grade in two halves: a coating family and a substrate hardness level. Get the family right and most of the decision is made. Here is the 43 family explained, and what to ask for when a Chinese plant quotes the equivalent.
Send us the grade code or a photo of the box. We identify the ISO class, confirm substrate and coating, and quote the closest equivalent made by a vetted Chinese plant. Free cross-reference, 48-hour quotation.
Sandvik's coated grades carry a GC prefix. The digits split into a coating family and a substrate hardness level, and the family is the part that matters most:
43 family is one coating on four substrates. GC4305, GC4315, GC4325 and GC4335 all carry the same thick CVD coating. The only thing that changes is the substrate: GC4305 is the hardest (most wear resistant), GC4335 the toughest. Between them they cover roughly P05 to P40.44 family, for instance) is a different coating chemistry aimed at a different balance, not a straight upgrade.CT and CC are CVD lines, CB is CBN for hardened steel, and plain alphanumeric codes like H13A are uncoated substrates for cast iron and non-ferrous work.| Grade | Family | ISO class | Where it belongs |
|---|---|---|---|
| GC4305 | 43 (CVD) | P05–P15 | Hardest grade in the 43 family. High-speed finishing where wear resistance dominates and the cut is uninterrupted. |
| GC4315 | 43 (CVD) | P15 (P05–P20) | Built to withstand high cutting temperatures, which is what allows high speed and long time-in-cut. Continuous to light-interrupted turning. Sandvik positions it as the option when you want maximum metal removal rate without giving up tool life. |
| GC4325 | 43 (CVD) | P25 (P10–P35) M15 (M5–M20) K20 (K10–K30) | The broadest grade in the family and the usual first choice for steel turning. Continuous to interrupted cuts, wet or dry. Its width is the point — it reduces the number of grades you have to keep on the shelf. |
| GC4335 | 43 (CVD) | P35–P45 | Toughest substrate in the family. Roughing, interrupted cuts, unfavourable conditions. |
| GC4205 | 42 (CVD) | P15 | Appears in Sandvik's own application charts alongside GC4315 at the P15 line — a different coating route to a similar class. |
| GC4235 | 42 (CVD) | P35 | Roughing end of the 42 family. |
| GC4415 / GC4425 | 44 (CVD) | P10 / P20–P25 | Later coating generation covering finishing through general steel turning. |
| GC4240 / GC4340 | 42 / 43 | P40 | Low-speed, high-impact interrupted machining. |
| GC1525 | CVD | M15–M25 | Stainless steel turning. |
| GC2220 | CVD | M / S | Stainless and heat-resistant alloys. |
| GC3010 / GC3210 | CVD | K01–K10 / K10–K20 | Cast iron finishing and semi-finishing. |
| H13A | Uncoated | K / N | Uncoated substrate for cast iron, aluminium and non-ferrous work. |
| CB7015 / CB7025 | CBN | H | Hardened steel and chilled cast iron — the classes where carbide life collapses. |
ISO classes for GC4205 / GC4315 / GC4325 / GC4235 are taken from Sandvik Coromant's own published application chart. The 43-family hardness ordering (GC4305 hardest → GC4335 toughest) follows the standard grade-designation convention documented by industry references.
The coating on GC4315 and GC4325 is not applied the way older CVD alumina was. Conventional alumina grows in randomly oriented crystals; Inveio grows them in one direction, in columns. Sandvik's stated consequences are a coating better able to resist cutting forces and heat, and reduced crack propagation — cracking in the alumina layer is how a CVD insert begins to spall.
The coating stack, from inside out: a cobalt-enriched surface gradient in the substrate, then a columnar MT-TiCN layer for abrasion resistance, then the alumina, then a bright yellow TiN top layer on the flank so an operator can see wear by eye.
Why this matters when you buy an equivalent: a plant can match the ISO class and the coating chemistry and still produce a different tool, because the difference lives in crystal orientation, layer thickness and the gradient zone. When we quote an equivalent to a GC grade, we ask the plant for the coating architecture and the measured thickness, not just the grade name.
A common mistake when moving work offshore is asking for a coated substitute in K or N class work. In cast iron and aluminium, a coating often adds heat and built-up edge rather than removing wear. Sandvik keeps uncoated grades in the catalogue for exactly this reason — H13A and its relatives. A quote that offers you a coated insert for grey cast iron has not understood the job.
| CVD (chemical vapour deposition) | PVD (physical vapour deposition) | |
|---|---|---|
| Thickness | 5–25 µm | 2–6 µm |
| Typical layers | MT-TiCN, Al2O3, TiN top coat | TiAlN, AlTiN, AlCrN, TiB2, DLC |
| Heat resistance | ~800 °C | ~900 °C |
| Edge condition | Thicker, more rounded edge | Sharper edge possible; can be ground then coated |
| Bond to substrate | Chemical bond, higher adhesion | Mechanical bond; residual compressive stress raises toughness |
| Best for | Roughing, steel and cast iron, high speed | Stainless, aluminium, titanium, finishing, interrupted cuts |
A coating specified at 3 µm of AlTiN frequently measures 1.5 µm on a delivered batch. We measure it by ball-crater (Calotest) and adhesion by Rockwell indentation before we accept a shipment.
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