22Cr12NiWMoV high temperature alloy

22Cr12NiWMoV is a typical martensitic precipitation-hardening stainless steel, also classified as a high-temperature alloy. By incorporating various strengthening elements (such as W, Mo, V, and Nb) into a low-carbon martensitic matrix and undergoing appropriate heat treatment, it achieves excellent high strength, good toughness, fatigue resistance, and a certain degree of corrosion and oxidation resistance at high temperatures (typically below 600°C).

DZ 2.11.31-2021, an industry standard issued by the Aviation Industry Corporation of China (AVIC), is known as the "Specification for Hot-Rolled and Forged Bars for Aeroengines." This standard strictly stipulates the technical requirements for alloy bars used in the manufacture of key hot-end components of aircraft engines (such as turbine disks, compressor disks, blades, and shafts), covering chemical composition, mechanical properties, microstructure, and ultrasonic testing.

The 22Cr12NiWMoV material based on the DZ 2.11.31-2021 standard represents that its quality fully meets the stringent requirements of the aviation engine field for high performance, high reliability and high consistency.

Key Features:

1) Combination of high strength and good toughness: Strengthening is achieved through martensitic transformation and subsequent aging treatment to precipitate intermetallic compounds (such as Laves phase) while maintaining sufficient toughness.

2) Excellent thermal strength: It can still maintain high strength, creep resistance and stress relaxation resistance in the temperature range of 550℃ ~ 620℃.

3) Good corrosion resistance and oxidation resistance: Contains about 12% chromium, which makes it more stable than ordinary alloy steel in high temperature atmospheric environment and certain corrosive media.

4) Excellent processing performance: good hot working formability (forging, rolling) and cutting performance.

Typical applications (in aircraft engines):

Turbine rotor blades: especially the working blades of the medium and low pressure turbines in the last few stages.

Compressor rotor blades and disks: used for the latter stages of disks and blades with higher operating temperatures.

Ring parts and fasteners: such as high-temperature bolts, springs and other key connecting parts.

It is also widely used in other high-end equipment manufacturing fields such as gas turbines and nuclear energy equipment.

This standard sets comprehensive requirements for 22Cr12NiWMoV bars to ensure their aviation-grade quality.

1) Chemical composition (melting analysis)

The standard has extremely strict control over the content range of alloying elements to ensure the stability and reproducibility of material properties.

2) Mechanical properties

The standard stipulates that the room temperature and high temperature mechanical properties of bars after a specific heat treatment system (usually quenching + tempering) must meet the following indicators (taking a common specification as an example, the specific values vary depending on the specification and heat treatment status):

High temperature durability (e.g. at 550°C/530MPa):

Durable life: ≥ 100 hours (specific test conditions and requirements will be specified in the standard)

3) Metallurgical quality and non-destructive testing

This is the core that distinguishes aviation standards from ordinary industrial standards, and the requirements are extremely high.

Macrostructure: The tower-shaped hairline inspection and acid immersion macrostructure shall not have defects such as shrinkage cavities, bubbles, cracks, inclusions, white spots, etc. that are visible to the naked eye.

High magnification structure: The grain size is usually required to be no less than level 4 (or as agreed), the structure is uniform, there is no overburning, and the delta ferrite content is controlled.

Non-metallic inclusions: There are extremely strict restrictions on the levels of A, B, C, and D inclusions (usually requiring the fineness to be ≤ level 1.5, or higher).

Ultrasonic flaw detection: 100% ultrasonic testing is carried out in accordance with the methods specified in the standards. Strict acceptance criteria are set for the size of equivalent flat-bottom hole defects (e.g. Φ1.2mm or smaller) to ensure that there are no harmful defects inside the material.

DZ standards usually recommend or specify heat treatment systems to ensure that the material achieves the expected performance. The typical aviation heat treatment system for 22Cr12NiWMoV is:

1) Quenching (Austenitizing) : Heat at 1020℃ ~ 1050℃, keep warm, then oil cool or air cool to obtain martensitic structure.

2) Tempering : Tempering is generally performed twice at 560°C to 580°C or higher, followed by air cooling after each hold. During the tempering process, dispersed strengthening phases are precipitated, achieving the optimal balance of strength and toughness.

22Cr12NiWMoV is a technologically mature, high-performance martensitic heat-resistant steel. When produced and controlled according to the DZ 2.11.31-2021 standard, its material properties, metallurgical quality, and consistency reach top-tier levels for aircraft engine applications. This standard, encompassing precise control of chemical composition, rigid mechanical performance specifications, and strict internal microstructure purity requirements, forms a crucial material foundation for ensuring safe, reliable, and long-life aircraft engine operation.

For engineers who choose this material, specifying compliance with the DZ 2.11.31-2021 standard means obtaining highly reliable material performance assurance in high-temperature and high-stress environments.