GGG-NiSiCr35-5-2 is the highest-nickel grade in this reference set of austenitic ductile (spheroidal-graphite) cast irons under German standard DIN 1694. Its designation numbers point to nominal weight-percent alloy targets of roughly 35% nickel, 5% silicon, and 2% chromium. That nickel level fully and robustly stabilizes the iron matrix as austenite, giving the casting excellent dimensional stability across repeated thermal cycles and resistance to the growth and thermal-fatigue cracking that eventually affects ordinary pearlitic or ferritic ductile iron in hot service. The silicon addition builds a protective oxide scale, and even at a relatively modest 2% chromium, the combination of high nickel and silicon gives this grade strong resistance to oxidation and thermal shock at sustained elevated temperature.

This grade corresponds closely to ASTM A439 Type D-5S, and its higher nickel content makes it the preferred choice in this family for the most demanding thermal applications: gas turbine housings and support rings, turbocharger housings, exhaust manifolds, and die blocks used in hot titanium pressing. Where the 20-5-2 and 30-5-2 grades offer a more economical middle ground, GGG-NiSiCr35-5-2 is specified when maximum dimensional stability under thermal cycling is the priority.

At roughly 35% nickel, GGG-NiSiCr35-5-2 has the most fully-developed austenitic matrix in this family, and it machines accordingly — more like a high-nickel austenitic stainless or nickel alloy than like any conventional cast iron. The matrix work-hardens readily under cutting pressure, so light cuts, a dull edge, or excessive dwell time will burnish the surface and make the next pass harder to engage cleanly. Consistent, adequate chip load and a genuinely sharp edge are essential to keeping this tendency under control.

Thermal conductivity drops further as nickel content rises, so this grade concentrates more cutting heat at the tool-chip interface than the lower-nickel NiSiCr grades in this family, let alone a standard ductile iron. That heat buildup is the main limiting factor on cutting speed and tool life here, more so than the material's bulk hardness would suggest. A coated carbide grade with good hot hardness, combined with a sharp, positively-oriented edge geometry, helps manage both heat and work hardening.

Chip control benefits from the spheroidal graphite structure, which still provides some internal chip-breaking despite the heavily austenitic matrix, but overall expect this to be the most demanding grade to machine in the NiSiCr family — run conservative cutting parameters and prioritize rigidity and coolant delivery over pushing speed.