Inconel 738 is a cast nickel-based superalloy — not a wrought material like most of the grades in this library — developed specifically for gas turbine blades that need to hold creep strength at extreme operating temperature. That wrought-vs-cast distinction matters in practice: 738 is produced as investment-cast components (equiaxed or, in specialized forms, directionally solidified), not rolled bar or plate, so shops rarely encounter it as generic stock. Its chemistry reflects that turbine-blade mission — nominally around 61% nickel, 16% chromium, 8.5% cobalt, 3.4% titanium, and 3.4% aluminum, with tungsten, molybdenum, tantalum, and niobium added in smaller amounts to reinforce high-temperature strength.

The titanium and aluminum content is deliberate: together they form the gamma-prime (γ′) precipitate phase that gives 738 its strength retention at temperatures approaching 980°C (1800°F), while the chromium content provides oxidation resistance in the hot combustion-gas environment turbine blades operate in. This combination of creep resistance, thermal-fatigue resistance, and oxidation resistance is what makes 738 (and its low-carbon variant, 738LC) a standard material for first- and second-stage turbine blades and vanes in aerospace and industrial gas turbines. Because it's supplied cast rather than wrought, both its stock form and its machining behavior differ meaningfully from wrought Inconel grades — a distinction worth keeping in mind before applying wrought-alloy machining assumptions to a 738 part.

738 carries every standard nickel-superalloy machining challenge — low thermal conductivity, rapid work hardening, high retained hot strength, and a strong tendency to gall against the tool — and then adds the complications that come with being cast rather than wrought. Its gamma-prime-strengthened microstructure, the same feature that gives it outstanding creep resistance in service, also makes it notably abrasive on cutting edges, and its high aluminum and titanium content pushes hot hardness higher than many other nickel grades.

Cast stock brings its own considerations on top of that. As-cast grain structure is coarser and less uniform than wrought bar, and depending on the casting process and section, there can be localized porosity or micro-shrinkage that affects surface finish and tool engagement in ways wrought material generally doesn't. Because 738 components are usually near-net-shape investment castings, machining is typically limited finishing work — cleaning up locating features, machining bolt holes, or finishing platform and root surfaces — rather than bulk stock removal. Light, controlled cuts with a sharp, positive-rake edge, conservative and consistent speeds, rigid workholding, and generous coolant to manage heat at the tool-chip interface are the standard approach. A coated carbide grade with strong hot hardness and toughness, matched to light finishing rather than heavy roughing, is the practical baseline for this alloy.