Inconel 600 in Thermal Cycling: Susceptibility to Cracking

300–700°C: Risk of sensitization and IGSCC increases.

Above 700°C: Creep becomes dominant; thermal fatigue is more likely.

Rapid heating/cooling rates: Increase thermal stress and fatigue damage.

Solution-annealed condition (typical for Inconel 600) provides the best resistance to SCC.

Cold-worked material has higher tensile strength but may be more susceptible to SCC under thermal cycling.

Grain size: Larger grains increase IGSCC susceptibility.

High-temperature water (nuclear applications): High SCC risk.

Caustic environments: Risk of caustic stress corrosion cracking (CSCC).

Oxidizing atmospheres: Can form protective Cr₂O₃ scales, reducing corrosion but not eliminating thermal fatigue.

To reduce cracking in Inconel 600 under thermal cycling, the following measures are commonly employed:

Control heating/cooling rates to minimize thermal stress.

Avoid restrained expansion through proper design (e.g., flexible supports).

Use low-sensitization welding procedures (low heat input, proper shielding).

Select appropriate fillers (e.g., Inconel 82/182 or 625) to improve weld ductility.

Apply stress relief heat treatment (though not always recommended for corrosion-sensitive applications).

Use corrosion inhibitors or modify the environment (e.g., in nuclear systems).

Regular inspection (UT, RT, ECT) to detect early cracking.

In summary:

Inconel 600 is not inherently prone to cracking under mild thermal cycling.

However, in severe thermal cycling combined with corrosive environments or restrained expansion, it can experience:

Thermal fatigue cracking

Intergranular stress corrosion cracking (IGSCC)

Weld and HAZ cracking

The material's cracking susceptibility is strongly influenced by temperature range, environment, stress levels, and welding practices. With proper design, welding procedures, and environmental control, Inconel 600 can perform reliably even under demanding thermal cycling conditions.