Application of nickel based alloys - Knowledge

1,Which Nickel-Based Alloys Can Be Used for Manufacturing Impellers of Acid and Alkali Solution Transfer Pumps?

Impellers of acid and alkali solution transfer pumps are subjected to severe corrosion from acidic/alkaline media and mechanical wear from fluid flow and solid particles. Nickel-based alloys selected for this application must have excellent corrosion resistance, high mechanical strength, and good wear resistance. The most commonly used grades are as follows:

Hastelloy C series (C276, C22, C4)

These are nickel-chromium-molybdenum-tungsten alloys with outstanding resistance to both oxidizing and reducing acids, such as sulfuric acid, hydrochloric acid, nitric acid, and mixed acids. They also exhibit excellent corrosion resistance in alkaline media like sodium hydroxide solutions.

Hastelloy C276 is the most widely used grade, with no carbide precipitation during welding, avoiding intergranular corrosion risks. It is suitable for impellers handling high-concentration acid-alkali solutions and mixed corrosive media.

Inconel 625

This alloy is strengthened by niobium, with high tensile strength, fatigue resistance, and corrosion resistance. It resists corrosion from dilute to moderate-concentration acids (hydrochloric acid, sulfuric acid) and alkaline solutions, and has good resistance to pitting and crevice corrosion.

It is ideal for impellers operating under medium-corrosion and high-mechanical-load conditions, such as transfer pumps for chemical wastewater containing acid-alkali components.

Monel 400

A nickel-copper alloy with excellent corrosion resistance in reducing acids (e.g., dilute hydrochloric acid, hydrofluoric acid) and alkaline media. It also has good wear resistance and low-temperature toughness.

It is suitable for impellers of pumps handling dilute acid-alkali solutions at moderate temperatures, but not recommended for strong oxidizing acid environments (e.g., concentrated nitric acid).

Alloy 20 (Nickel-iron-chromium alloy)

Though classified as a nickel-iron-chromium alloy, it has high nickel content (32%–38%) and excellent corrosion resistance in sulfuric acid, phosphoric acid, and alkaline solutions. It also has good weldability and cost-effectiveness.

It is a cost-efficient choice for impellers of pumps handling low-to-medium concentration acid-alkali solutions in general chemical processes.

The selection of nickel-based alloys for impellers should be based on the concentration of acid/alkali media, operating temperature, fluid velocity, and presence of solid particles to balance corrosion resistance, mechanical performance, and economic efficiency.

2,What Are the Specific Applications of Nickel-Based Alloys in Automobile Exhaust Gas Treatment Systems?

Automobile exhaust gas treatment systems operate in harsh environments characterized by high temperature, corrosive gas, and mechanical vibration. Nickel-based alloys are widely used in this field due to their excellent high-temperature oxidation resistance, corrosion resistance, and structural stability. Their specific applications are as follows:

Substrates and honeycomb carriers of catalytic converters

The catalytic converter is the core component of exhaust gas treatment. Nickel-based alloys (e.g., Inconel 600, 601) are used to make the metal honeycomb carrier, replacing traditional ceramic carriers.

These alloys can withstand continuous high temperatures (up to 1000℃) and thermal shocks during engine start-stop cycles, and their high thermal conductivity ensures uniform temperature distribution, improving catalytic efficiency. In addition, they have good corrosion resistance to acidic exhaust components (e.g., sulfur oxides, nitrogen oxides).

Exhaust manifold liners and connecting pipes

The exhaust manifold directly collects high-temperature exhaust gas from the engine cylinder, with operating temperatures reaching 800–900℃. Nickel-based alloys (e.g., Hastelloy X, Inconel 718) are used to make liners or integral manifolds to resist high-temperature oxidation and thermal fatigue.

Compared with stainless steel, nickel-based alloys have better creep resistance at high temperatures, avoiding deformation and cracking caused by long-term thermal stress. They also resist corrosion from condensed acidic water formed during cold starts.

Diesel particulate filter (DPF) components

For diesel engines, DPF is used to capture particulate matter in exhaust gas. Nickel-based alloy fibers (e.g., alloy 617) are used to make filter materials or reinforcing structures.

These alloys have high-temperature strength and oxidation resistance, and can withstand the high temperatures (up to 1200℃) generated during DPF regeneration (combustion of trapped particulates), while resisting corrosion from sulfur-containing exhaust gas.

Sensors and actuators in exhaust treatment systems

Key sensors (e.g., oxygen sensors, NOₓ sensors) and actuators in exhaust systems require materials with stable performance at high temperatures. Nickel-based alloys (e.g., Inconel 625) are used to make sensor protection sleeves and actuator components.

They can maintain structural integrity in high-temperature and corrosive exhaust environments, ensuring accurate and stable operation of sensors and actuators for a long time.

In summary, nickel-based alloys play an irreplaceable role in improving the durability and efficiency of automobile exhaust gas treatment systems, helping to reduce harmful emissions and meet strict environmental standards.