Wear mechanism study of exhaust valve system in modern heavy duty combustion engines

• Published in: Wear 2011-07, Vol.271 (9), p.2477-2484
• Main Authors: Forsberg, P., Hollman, P., Jacobson, S.
• Format: Article
• Language: English
• Subjects: Accumulation; Adhesive; Applied sciences; Combustion; Corrosive; Engineering Science with specialization in Materials Science; Engines; Exact sciences and technology; Exhaust valve system; Friction, wear, lubrication; Fundamental areas of phenomenology (including applications); Inelasticity (thermoplasticity, viscoplasticity...); Machine components; Mechanical engineering. Machine design; Oxidative; Physics; Protective coatings; Solid mechanics; Soot; Structural and continuum mechanics; Teknisk fysik med inriktning mot materialvetenskap; Valves; Wear; Wear mechanisms
• ISSN: 0043-1648; 1873-2577; 1873-2577
• DOI: 10.1016/j.wear.2010.11.039

► Three pairs of exhaust valves and valve seat inserts from diesel engines investigated. ► Different running conditions has lead to varying amounts of wear and surface appearances. ► 1 to 5 μm thick tribofilms with protective properties on low wear specimens. ► Tribofilm consists of residues from fuel and lubricant additives. ► No protective tribofilm on specimens from cleaner engine. The increasing demands from environmental legislations are changing the conditions that the valve system is exposed to in heavy duty engines. Increased pressures, higher temperatures and lower amounts of soot which can build up a protective film are some of the increasing challenges which the system has to endure. Three pairs of valves and valve seat inserts with the same material and design properties but with different service condition have been analyzed with a variety of analytical instruments to gain information of how the wear occurs. The wear mechanisms found were a combination of oxidation, where many different oxides were found, adhesive wear, which was seen both in form of material transfer and flow lines. On top of Sample Mild and Hard there were tribo films of thickness varying from 1 to 5 μm consisting of Ca, O, P, S and Zn. The film has in all cases protected the underlying surface from wear but in some cases seems to have a corrosive impact instead.