How to Choose Casting Material: Stainless Steel vs Alloy Steel vs Hastelloy

Why Material Selection Matters

The material you choose determines not only the performance of your part, but also its cost, lead time and manufacturability. A wrong material choice can lead to premature failure in service, corrosion problems, or unnecessary costs that could easily have been avoided.

For precision investment casting, the most commonly specified material families are stainless steel, alloy steel, duplex stainless steel, nickel-based alloys (Hastelloy) and copper alloys. Each family has distinct properties, price points and applications.

Quick Comparison Table

Material	Typical Grades	Corrosion Resistance	Temperature Range	Relative Cost	Common Applications
Stainless Steel	304, 316, CF8, CF8M, 316L	Good to Excellent	-196°C to 800°C	$ (Baseline)	Pumps, valves, food equipment
Alloy Steel	4140, 42CrMo, 45#	Poor to Moderate	-40°C to 500°C	$ (Similar to SS)	Structural parts, gears, shafts
Duplex 2205	2205, S31803, S32205	Excellent (pitting/crevice)	-50°C to 300°C	$$ (1.5-2x SS)	Offshore, chemical, marine
Hastelloy	C276, CW2M, N10276	Superior (extreme media)	-196°C to 1000°C	$$$$ (5-8x SS)	Chemical processing, severe service
Copper Alloy	Brass, Bronze, CuNi	Good (specific media)	-200°C to 300°C	$$ (2-3x SS)	Marine fittings, electrical parts

1. Stainless Steel Castings (304, 316, CF8M)

Stainless steel is the workhorse of investment casting. It offers an excellent balance of corrosion resistance, mechanical strength and cost. For investment casting, grades are typically specified in their cast equivalents: CF8 (304), CF8M (316) and CF3M (316L).

Best for:

• Pump impellers, casings and valve bodies
• Food and beverage processing equipment
• Pharmaceutical and sanitary applications
• General industrial machinery components

2. Alloy Steel Castings (4140, 42CrMo, 45#)

Alloy steels offer high strength and wear resistance at a very attractive cost. They are typically heat treated (quenched and tempered) to achieve the desired mechanical properties. However, they have limited corrosion resistance and usually require protective coating or plating for corrosive environments.

Best for:

• Structural and mechanical components
• Gears, sprockets and wear parts
• Automotive and agricultural machinery parts
• Applications where strength matters more than corrosion resistance

3. Duplex Stainless Steel 2205 Castings

Duplex 2205 combines high strength (roughly twice that of 316) with excellent corrosion resistance, particularly against chloride stress corrosion cracking. It is the material of choice for demanding offshore, chemical and marine applications.

Best for:

• Offshore and marine equipment
• Chemical processing vessels and piping
• Heat exchangers and seawater systems
• High-pressure applications with corrosive media

4. Hastelloy Castings (C276, CW2M)

Nickel-based alloys like Hastelloy C276 offer the highest level of corrosion resistance available, particularly against strong acids, oxidizing and reducing media. They are expensive — often 5 to 8 times the cost of stainless steel — but indispensable for severe service conditions.

Best for:

• Chemical and petrochemical processing equipment
• Flue gas desulfurization systems
• Pollution control and waste treatment
• Pharmaceutical reactors and high-purity systems

5. Copper Alloy Castings (Brass, Bronze)

Copper alloys offer excellent thermal and electrical conductivity, natural lubricity, and good corrosion resistance in marine environments. They are commonly used for marine hardware, electrical components and wear parts.

Best for:

• Marine propellers and fittings
• Electrical and thermal components
• Bearing and wear surfaces
• Decorative and architectural hardware

How to Decide: A Step-by-Step Approach

1. Identify the service environment — What media, temperature and pressure will the part face?
2. Define required mechanical properties — Strength, hardness, wear resistance?
3. Consider corrosion requirements — Is the part exposed to chlorides, acids or seawater?
4. Check temperature range — Some alloys lose strength or become brittle outside their range.
5. Evaluate cost vs. performance — The most expensive material is not always the best choice.
6. Consult the foundry early — Experienced casters can suggest cost-saving alternatives with equivalent performance.

Cost Considerations

Material Family	Relative Alloy Cost	Typical Use Case
Alloy Steel	0.8x - 1.0x	Cost-sensitive structural parts
Stainless Steel	1.0x (baseline)	General corrosion-resistant parts
Copper Alloy	2x - 3x	Marine, electrical, wear parts
Duplex 2205	1.5x - 2x	Offshore, chemical, high-strength
Hastelloy C276	5x - 8x	Extreme corrosion service