Different applications of INCONEL alloy 625 and 725

The INCONEL® alloys 625 and 725 differ in composition, strengthening mechanisms, and properties, resulting in distinct application focuses. The core difference lies in the requirements for "high-temperature stability" and "high strength". The following is a detailed description of their specific applications: 

I. Typical Applications of INCONEL® 625

625 is mainly characterized by solid solution strengthening and possesses excellent high-temperature stability, corrosion resistance, and machinability. It is mainly used in high-temperature + highly corrosive environments, especially suitable for scenarios that require both "high-temperature strength" and "resistance to complex medium corrosion".

1. Energy and Power Sector

Energy generation: Combustion chambers, transition sections, flame tubes, etc. (required to withstand 800-1000℃ high temperatures and gas corrosion).

Aerospace: Exhaust pipes of engines, turbine outer rings, spacecraft propulsion system pipelines (resistant to high-temperature oxidation and high-speed airflow erosion).

Nuclear power: Heat exchange tubes of nuclear reactors, steam generator pipes (resistant to high-pressure water corrosion and radiation environment).

2. Chemical and Environmental Protection Sector

Chemical equipment: Heat exchangers, reactor linings, agitators (resistant to strong reducing media such as hydrochloric acid and sulfuric acid and high-temperature high-pressure corrosion).

Sulfur dioxide removal: Spray systems of desulfurization towers, absorption pipe systems (resistant to acidic corrosion of sulfur-containing flue gas).

Seawater desalination: Reverse osmosis membrane modules, seawater treatment pump impellers (resistant to point corrosion and crevice corrosion of seawater chloride ions).

3. Other Industrial Scenarios

Marine engineering: Seawater cooling system pipelines, underwater drilling platform connectors (resistant to long-term immersion corrosion in seawater).

Precision instruments: Protective sleeves for high-temperature thermocouples (required to maintain structural stability and corrosion resistance at high temperatures). 

II. Typical Applications of INCONEL® 725

725 is based on precipitation hardening and achieves extremely high yield strength (800-1000 MPa) through aging treatment. It is mainly used in medium-temperature (≤ 650°C) and high-pressure environments, and is particularly suitable for scenarios that require "high strength + corrosion resistance" in combination.

1. Oil and Gas Extraction Field

Downhole tools: oil pipes, casing, packers, safety valves (must withstand high pressure in oil and gas wells (over 100 MPa), H₂S/CO₂ corrosion and formation stress).

Wellhead equipment: high-pressure valves, flanges, connectors (resist high-pressure impacts and sulfide stress corrosion in oil and gas extraction).

2. Marine and Deep-sea Engineering

Deep-sea pipelines: joint and fasteners for deepwater oil and gas transportation pipelines (must withstand deep-sea high pressure (increasing by 10 MPa per 100 meters) and seawater corrosion).

Ocean structures: high-strength bolts for platforms, anchor chain connections (balance high load-bearing capacity and seawater corrosion).

3. High-pressure Vessels and Machinery

High-pressure vessels: inner linings and domes of chemical high-pressure reactors (must withstand medium-temperature high-pressure medium corrosion and structural stress).

Precision machinery: heavy-duty bearings, transmission shafts (maintain high strength and wear resistance in medium-temperature environments). 

III. The Core Reason for the Differences in Applications

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In short, 625 is the "all-rounder for high-temperature corrosion resistance", while 725 is the "specialist in medium-temperature and high-pressure environments". The two have no direct substitution in their respective areas of expertise.

Tags: Cold facts about alloys