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Proposal of Characterization Procedure of Metal⁻Graphite Interface Strength in Compacted Graphite Iron
Edwin A Lopez-Covaleda1, Sepideh Ghodrat2, Leo A I Kestens3
1Metals Science and Technology Group, EEMMeCS Dept., Ghent University; Technologiepark 903, 9052 Gent, Belgium. edwinalexis.lopezcovaleda@ugent.be.
Materials (Basel, Switzerland)
|July 11, 2018
Summary
Compacted graphite iron (CGI) is crucial for heavy-duty truck engine heads. Heat treatment enhances the metal-graphite interface strength, improving material durability against thermomechanical fatigue.
Area of Science:
- Materials Science
- Mechanical Engineering
- Metallurgy
Background:
- Compacted graphite iron (CGI) balances mechanical and thermal properties for heavy-duty truck engine cylinder heads.
- Graphite particles in CGI act as stress concentrators, leading to crack initiation during thermomechanical fatigue cycles.
- Understanding the metal-graphite interface is critical for improving CGI's fatigue resistance.
Purpose of the Study:
- To characterize the metal-graphite interface strength in CGI.
- To compare the interface properties of as-cast CGI with heat-treated CGI.
- To investigate the effect of microstructure changes on interface delamination resistance.
Main Methods:
- Scratch testing was employed to evaluate the metal-graphite interface strength.
- Microstructural analysis was performed on as-cast and heat-treated CGI samples.
- Heat treatment involved annealing at 700°C for 60 hours.
Main Results:
- As-cast CGI featured a pearlitic matrix with smooth graphite-ferrite interfaces.
- Heat-treated CGI exhibited a decomposed pearlitic structure with spiky ferrite-graphite interfaces.
- Scratch tests revealed significantly higher delamination resistance for spiky ferrite-graphite interfaces compared to smooth ones.
- Mechanical interlocking of graphite spikes with ferrite contributes to enhanced interface strength.
Conclusions:
- Heat treatment modifies CGI microstructure, creating spiky graphite-ferrite interfaces.
- The spiky morphology and mechanical interlocking at the ferrite-graphite interface enhance delamination resistance.
- Optimizing the metal-graphite interface through heat treatment can improve the fatigue life of CGI components.
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