Difference between G3 and G30 Hastelloy - Knowledge

G3 and G30 Hastelloy are both nickel-chromium-molybdenum (Ni-Cr-Mo) superalloys designed for excellent corrosion resistance, but they differ significantly in chemical composition, corrosion resistance performance, and typical applications.

1. Core Difference: Chemical Composition

The primary distinction lies in their elemental content, especially for chromium (Cr), molybdenum (Mo), and copper (Cu). These elements directly determine their corrosion resistance and mechanical properties.

Element (Weight %)	Hastelloy G3	Hastelloy G30	Key Impact of Difference
Nickel (Ni)	~44-48%	~43-47%	Similar base content, ensuring general alloy stability.
Chromium (Cr)	~21-23%	~28-31%	G30 has much higher Cr, enhancing resistance to oxidizing media (e.g., nitric acid, high-temperature air).
Molybdenum (Mo)	~6-8%	~4-6%	G3 has higher Mo, improving resistance to reducing media (e.g., sulfuric acid, hydrochloric acid).
Copper (Cu)	~1.5-2.5%	~1.0-1.6%	G3 has slightly higher Cu, boosting resistance to sulfuric acid and phosphoric acid.
Tungsten (W)	~1.5-2.5%	~0.2-0.6%	G3's higher W further enhances resistance to pitting and crevice corrosion.
Iron (Fe)	~18-21%	~14-17%	G3 has more Fe, reducing cost slightly but with minimal impact on corrosion resistance.

2. Corrosion Resistance Performance

Their composition differences lead to distinct advantages in resisting different types of corrosive environments.

Hastelloy G3

Strengths: Excels in reducing corrosive media due to higher Mo and W content. It performs well in dilute to moderate concentrations of sulfuric acid, hydrochloric acid, and phosphoric acid.

Limitations: Its lower Cr content makes it less effective in strong oxidizing environments, such as concentrated nitric acid or high-temperature oxidizing atmospheres.

Hastelloy G30

Strengths: Dominates in oxidizing corrosive media thanks to its high Cr content. It resists concentrated nitric acid, mixed acids (e.g., nitric-sulfuric acid), and high-temperature oxidizing gases.

Limitations: Lower Mo content reduces its performance in strong reducing media compared to G3, especially in concentrated hydrochloric acid.

3. Typical Applications

Their unique corrosion resistance profiles make them suitable for different industrial scenarios.

Hastelloy G3

Chemical processing: Equipment for producing sulfuric acid, phosphoric acid, and organic acids.

Petrochemical industry: Reactors, heat exchangers, and pipelines handling sour crude oil or acidic process streams.

Pollution control: Scrubbers and exhaust systems for treating acidic flue gases (non-strong oxidizing).

Hastelloy G30

Chemical processing: Vessels and pipelines for concentrated nitric acid, nitric-sulfuric acid mixtures, and chromic acid.

Nuclear industry: Components in nuclear fuel reprocessing (resisting strong oxidizing radioactive solutions).

Waste treatment: Equipment for incineration plants and hazardous waste disposal (handling high-temperature oxidizing and acidic wastes).

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4. Mechanical Properties & Other Differences

Aspect	Hastelloy G3	Hastelloy G30
Tensile Strength	~690 MPa (room temperature)	~720 MPa (room temperature)
Yield Strength	~310 MPa (room temperature)	~345 MPa (room temperature)
Ductility (Elongation)	~40%	~35%
Cost	Slightly lower (higher Fe, lower Cr)	Higher (higher Cr content)

In summary, G3 is preferred for reducing corrosive environments, while G30 is the top choice for oxidizing or mixed oxidizing-reducing environments. The selection between them depends entirely on the specific corrosive conditions of the application.