Directed Solidified (DS) Turbine Blades

Technological Foundation:

The DS (Directionally Solidified) production method is based on the principle of controlled solidification of the metal in a specific direction (usually the vertical axis). This method ensures that crystals grow in only one direction during casting, eliminating the formation of grain boundaries only in the longitudinal direction and eliminating crosswise or randomly oriented grain boundaries.

This particularly enhances creep resistance and fatigue life, as grain boundaries are weak areas where creep cracks can easily propagate.

Production Steps:
1. Ceramic molding is performed (investment casting process).

2. The mold is placed in the casting furnace.

3. The liquid superalloy is poured under vacuum.

4. The mold is pulled downward in a controlled manner in a temperature gradient, ensuring directed solidification.

Advantages:

Because grain boundaries are eliminated, creep and thermal fatigue life are significantly increased.
DS-produced blades have a lifespan 3-5 times longer than conventionally cast blades.
Fewer microstructure defects ensure higher performance and reliability.
Application Examples:
Fighter aircraft engines (F110, EJ200, etc.)
Helicopter turboshaft engines
High-temperature industrial gas turbines

Single Crystal (SX) Turbine Blades

Scientific Basis:
SX (Single Crystal) turbine blades are high-performance turbine components composed entirely of a single crystal structure, meaning they contain no grain boundaries. This manufacturing technology is more advanced than the DS method and aims to completely eliminate the following problems:

Creep cracks that may occur at grain boundaries
Oxidation/corrosion along grain boundaries
Mechanical weaknesses due to grain orientation
With the SX production method, the fin solidifies starting from the crystal nucleus, without any branching.

Production Process:

1. A seed crystal is placed at the bottom of the casting mold.

2. As solidification progresses, only this crystal continues to grow.

3. A spiral nucleator (helix selector) or starter block is used to achieve unidirectional crystal formation.

4. Ultimately, the entire wing structure emerges as a single crystal.

Microstructure and Performance Properties:

• High strength with up to 70% γ′ phase ratio
• Thermal stability up to 1200–1300°C
• Service life over 20,000 hours
• Excellent aero-thermal performance in rotor or stator parts
Critical Areas of Use:
• In the engines of 5th-generation fighter jets like the F-35 (e.g., P&W F135)
• In space engines and hypersonic vehicle engines
• In high-efficiency power plants