Heat treatment sets the internal structure of a nickel alloy bar, and therefore its strength, corrosion resistance, and stability in service. Southerly Alloy supplies nickel alloy bars in the full set of heat-treated conditions — solution annealed, age hardened, stress relieved, homogenized, and bright annealed — with full mill certification on every heat.
Nickel Alloy Heat Treatment Processes
Nickel alloys are strengthened by precipitation (gamma prime and gamma double prime), not by martensitic quench as in steel. The core processes are:
- Solution annealing (980–1230 °C, water quench or air cool) dissolves precipitated phases and homogenizes the structure. For Inconel 625, the range is 980–1150 °C.
- Age hardening (650–900 °C, single or double stage) precipitates gamma prime and gamma double prime for a large rise in strength. Inconel 718 uses a double stage: 720 °C for 8 hours, then 620 °C for 8 hours.
- Stress relief (425–870 °C) removes machining and welding residual stress to guard against cracking. Monel 400 is relieved at 540–565 °C.
- Homogenizing (high temperature, long time) removes casting and forging segregation in the billet.
- Stabilizing (600–900 °C, slow cool) keeps carbides even and controls topologically close-packed phases in niobium-bearing alloys.
- Grain-refinement anneal (just below solution) refines the grain for fatigue service.
- Bright annealing (controlled atmosphere) gives a scale-free, bright surface.
- Solution anneal plus aging combines the two steps for the final service condition.
Steel Heat Treatment — A Separate Route
Quenching, tempering, normalizing, and through-hardening are steel processes based on martensitic transformation. They do not apply to precipitation-strengthened nickel alloys, so we list them only to avoid confusion. Our supply covers the nickel alloy conditions described above; for carbon and alloy steels, specify the steel grade and condition separately.
Deep Dive
Our guide Nickel Alloy Heat Treatment: Solution Annealing & Aging explains the metallurgy and the typical parameters for each grade.
Condition and Supply
Heat-treated condition is one part of the delivered bar; the forming route and surface finish complete it. See our Bar Manufacturing Process guide and Bar Surface Finishes & Finishing guide. The full bar catalogue is at Bars and rods by grade.
Frequently Asked Questions
What does solution annealing do for a nickel alloy bar?
It dissolves precipitated phases and evens the structure, which restores corrosion resistance and prepares the bar for age hardening.
Can a bar be supplied already age hardened?
Yes. Solution-annealed plus age-hardened is a common final condition, especially for Inconel 718 and similar grades.
Why is stress relief specified after machining?
Machining leaves residual stress that can drive cracking in service; a stress-relief anneal removes it before the part ships.
Are mill certificates provided?
Every heat travels with an EN 10204 3.1 mill certificate.
Request a Quote
Tell us the grade, shape, diameter, heat-treated condition, and quantity. Southerly Alloy returns a quoted price, lead time, and the certificate package in one reply.