Microstructure Evolution Control and Performance Degradation of SA-178 Grade C Boiler Tubes Driven by Pearlite...

Area of Science:

• Materials Science
• Metallurgy
• Engineering

Background:

• Boiler tubes made of SA 178 grade C carbon steel are vital in the energy sector.
• Degradation of boiler tube service life can cause costly operational shutdowns.
• Microstructural evolution, specifically pearlite transformation, impacts material integrity.

Purpose of the Study:

• To investigate the effect of microstructural changes on the service life of SA 178 grade C carbon steel boiler tubes.
• To understand the transformation of lamellar pearlite into spheroidized pearlite.
• To correlate microstructural evolution with mechanical property degradation.

Main Methods:

• Small-Angle X-ray Scattering (SAXS) for microstructural analysis.
• Metallographic analysis, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray (EDX) Spectroscopy.
• Mechanical testing to evaluate tensile strength and hardness.

Main Results:

• SA 178 steel microstructure evolves from ferrite and lamellar pearlite to spheroidized pearlite.
• Tensile strength decreases from 523 MPa (0% spheroidization) to 335 MPa (100% spheroidization).
• Hardness reduces from 175 HV to 89 HV with increasing spheroidization.

Conclusions:

• Spheroidization of pearlite is a key factor in the degradation of SA 178 boiler tubes.
• Microstructural changes directly correlate with reduced mechanical properties and service life.
• Understanding this transformation is critical for preventing boiler failures.