How does Inconel 718 high-temperature alloy improve strength through heat treatment?

A must-read for the aviation and energy industries! How does Inconel 718 high-temperature alloy improve strength through heat treatment?

718 (Inconel 718) round steel solution + aging heat treatment process
Inconel 718 is a nickel-based precipitation hardening high-temperature alloy, commonly used in high-temperature and high-stress environments such as aerospace, gas turbines, oil and gas, and nuclear industries. In order to obtain the best mechanical properties, high-temperature strength and corrosion resistance, a heat treatment process of solution treatment + aging treatment is usually used.

1. Inconel 718 round steel solution + aging heat treatment process
① Solution treatment

Purpose:
To completely dissolve the metal elements (such as Nb, Ti, Al, Cr) in the alloy to form a uniform austenite matrix.

Eliminate processing stress and improve the plasticity and toughness of the material.

Process parameters:
Temperature: 980-1065℃
Hot holding time: 1-2 hours (depending on the rod diameter)
Cooling method: Air cooling (AC) or water cooling (WQ)
Recommendation:
1065℃
Solution treatment is suitable for applications requiring the highest toughness (such as aircraft engine components).
980℃
Solution treatment is suitable for applications requiring higher creep resistance (such as gas turbine components).

②Aging Treatment
Purpose:
The yield strength, creep resistance and high temperature stability of Inconel 718 are significantly improved through precipitation strengthening (γ' and γ'' phase precipitation).
Standard two-stage aging process (suitable for most applications)

Heat Treatment Process

Analysis:

720-760℃: Promote the precipitation of γ'' phase (Ni3Nb) and γ' phase (Ni3(Al,Ti)), improve the yield strength and creep resistance of the alloy.
620℃ Secondary aging: Optimize the precipitation phase, increase the plasticity and fracture toughness of the material.

2. Typical heat treatment process of Inconel 718 round steel

Process 1: Standard high-strength heat treatment (most common)
Solution treatment: 980-1065℃, 1-2 hours, air cooling (AC)
Aging treatment: 720℃ × 8 hours, then furnace cooling to 620℃ 620℃ × 8 hours, then air cooling (AC)

Applicable scenarios:
Applicable to high-temperature and high-strength applications such as aircraft engines, gas turbines, high-temperature fasteners, and nuclear industry.

Process 2: Optimized high-toughness heat treatment
Solution treatment: 1065℃ × 1-2 hours, air cooling (AC)
Aging treatment: 760℃ × 10 hours, then furnace cooling to 650℃ 650℃ × 10 hours, then air cooling (AC)

Applicable scenarios:
Applicable to low-temperature impact load applications, such as aerospace structural parts, supersonic aircraft parts, etc.

3. Properties after heat treatment (standard Inconel 718)

Material Performance Specifications

4. Important Notes

🔹 Solution cooling method: air cooling or water cooling, avoid too slow cooling, otherwise it will cause Laves phase precipitation and reduce material toughness.
🔹 Strict control of aging holding time: too long may cause grain growth and reduce fatigue resistance.
🔹 Avoid excessive temperature treatment: exceeding 980℃ may cause grain boundary embrittlement and reduce material performance.
🔹 Bar diameter affects heat treatment time: large-sized bars require longer holding time to ensure uniform treatment.

The solution treatment temperature of Inconel 718 round steel is 980-1065℃, and the aging treatment usually adopts a two-stage aging process of 720℃ × 8h + 620℃ × 8h.
Different heat treatment schemes can optimize strength, toughness or high temperature resistance, and are suitable for different aerospace, petroleum, and nuclear industry applications.
The heat treatment process requires precise control of cooling rate and aging time to obtain the best structure and performance.

If your Inconel 718 round steel has a specific size or special application requirements, the heat treatment solution can be further optimized. Welcome to communicate! 😊