Morphology and mechanisms of cavitation damage on lamellar gray iron surfaces

• Published in: Wear 2020-09, Vol.456-457, p.203324, Article 203324
• Main Authors: Abreu, Marcio, Sundberg, Jill, Elfsberg, Jessica, Jonsson, Stefan
• Format: Article
• Language: English
• Subjects: Cavitation; Cavitation erosion; Chipping; Combustion chambers; Cylinder liners; Damage patterns; Diesel engines; Engine components; Engine coolants; Flake graphite; Flakes; Graphite; Gray iron; Lamellar cast iron; Materials Science and Engineering; Morphology; Roughening; Service life; Steadite; Teknisk materialvetenskap; Ultrasonic testing
• ISSN: 0043-1648; 1873-2577; 1873-2577
• DOI: 10.1016/j.wear.2020.203324

Engine parts in contact with liquids may suffer cavitation erosion damage. Understanding its mechanisms in realistic operating environments is necessary for improvements in the service life and durability of materials for heavy-duty diesel engines. This work illustrates the cavitation erosion behavior of a cylinder liner material with a follow-up of detailed, high-magnification SEM images of damaged sites on the surface. The cylinder liner encloses the piston and combustion chamber in the engine of large trucks and its material of choice is usually a lamellar gray cast iron, its microstructure consisting of flake-shaped graphite, a pearlitic matrix and some steadite. Testing was carried out using an ultrasonic vibratory apparatus, and the liquid of choice was a commercial engine coolant composed of water, glycol and inhibitors. Based on observations of tested surfaces, a sequence of damage patterns is proposed as an explanation of the material’s cavitation erosion behavior. Initiation consists of: chipping at graphite cluster centers, graphite flake removal, pitting along graphite flakes and direct matrix pitting. Development consists of: evolution of chipped spots into matrix-damaging pits, radial pit expansion, pit merging and surface roughening. It can be concluded that presence and morphology of graphite are critical to the cavitation erosion behavior of LGI. •Graphite is crucial to the cavitation erosion behavior of flake graphite irons.•Damage is observed at very early stages of exposure to cavitation.•Early- and late-stage damage mechanisms are illustrated.•A detailed follow-up of the surface damage evolution is presented.