Surface Condition Evolution and Fatigue Evaluation after Different Surface Processes for TiAl₄₇Cr₂Nb₂ Alloy

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Titanium-aluminum-niobium alloys are crucial for high-temperature applications.
• Surface integrity significantly influences the fatigue life of metallic components.
• Understanding the effect of surface treatments on alloy performance under thermal stress is vital.

Purpose of the Study:

• To investigate the effect of different surface treatments on the fatigue performance of TiAl47Cr2Nb2 alloy.
• To analyze surface condition evolution and hardness changes after thermal exposure.
• To determine the optimal surface treatment for enhanced fatigue resistance.

Main Methods:

• Investment casting of TiAl47Cr2Nb2 alloy specimens.
• Application of three surface processes: sand-blasting (SB), sand-blasting and shot-peening (SBSP), and sand-blasting and mechanical grinding (SBMG).
• Thermal exposure at 700 °C for 24 hours, followed by surface roughness and hardness measurements, and fatigue testing.

Main Results:

• Surface roughness (Ra) values were 3.14 µm (SB), 2.35 µm (SBSP), and 0.04 µm (SBMG), remaining stable after thermal exposure.
• SB induced saturated work hardening; SBMG resulted in lower initial hardness due to removal of the hardened layer.
• Hardness significantly recovered after thermal exposure for all treatments.
• SBMG specimens exhibited the highest fatigue limit (350 MPa).

Conclusions:

• The sand-blasting and mechanical grinding (SBMG) process yields the smoothest surface, crucial for high fatigue performance.
• Despite lower initial hardness, the SBMG surface finish and residual work hardening contribute to superior fatigue resistance.
• Surface treatment optimization is key to maximizing the fatigue life of TiAlCrNb alloys in demanding environments.