---
name: nickel-superalloys
title: Reason Over Nickel Superalloy Behavior
description: Apply the strengthening-phase framework (gamma-prime, gamma-double-prime, solid solution), heat-treatment sensitivity, additive-manufacturing segregation and high-temperature service behavior of the nickel superalloy family. Grade-specific facts come from the scientist's data or cited sources, not from this skill.
keywords:
- level:L1
- materials
- nickel-superalloys
---

## Identify the strengthening family first

Nickel superalloys fall into three strengthening families, each with its own
precipitation kinetics and so its own heat-treatment sensitivity:

- gamma-prime (Ni3(Al,Ti)) precipitation-strengthened grades;
- gamma-double-prime (Ni3Nb) precipitation-strengthened grades, where
  gamma-prime is usually a secondary contributor;
- solid-solution-strengthened grades.

Name which phase a claim is about; "the strengthening phase" is ambiguous in
grades that carry more than one. Equilibrium phases matter too: in
niobium-bearing grades, delta phase (Ni3Nb, orthorhombic) forms on over-ageing
or slow cooling and, at grain boundaries, can usefully pin grain size or
embrittle the material depending on its morphology and amount.

## Heat treatment and precipitate state

Strength from gamma-prime and gamma-double-prime depends on precipitate size
(under-, peak- or over-aged) more strongly than most other strengthening
mechanisms. State the schedule that produced the claimed state (solution
temperature and time, single or double ageing, cooling rate; see
`heat-treatment`) and the precipitate morphology the property depends on. A
property claim holds only for the schedule that produced it.

## Additively manufactured material

As-built additive material differs from wrought or cast material of the same
nominal grade:

- columnar grains grown along the build direction give anisotropic
  properties (`build-orientation`);
- rapid solidification segregates alloying elements; in niobium-bearing
  grades this appears as interdendritic Laves phase, distinct from the delta
  phase of wrought material;
- final properties depend strongly on the post-build heat-treatment route
  chosen to dissolve or control that segregation.

Do not apply wrought handbook properties to additive material of the same
grade without checking these.

## Service behavior

High-temperature service is why this family is chosen: creep resistance,
oxidation and corrosion resistance, and microstructural stability (precipitate
coarsening, formation of embrittling phases) under long exposure. A
room-temperature property alone does not qualify a superalloy for its
service.

## Return

The strengthening family and the phases the claim depends on, the
heat-treatment schedule and precipitate state, whether the material is
wrought, cast or additive, the service-temperature regime the claim applies
to, and the grade-specific values used with their source.