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Effects of APS Coating on Wear Characteristic of Internal Combustion Engine's Cylinder

Ghorashi, Mir Siavash | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42357 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farrahi, Gholamhossein; Yousefi, Reza
  7. Abstract:
  8. The quest for increasing the efficiency of internal combustion engines is going on since the invention of automobile in the world. Wear between cylinder and ring is one of the major parameters reducing the engine performance. So many parameters are affecting the wear losses. Temperature plays a key role on the severity of wear condition in internal combustion engines. In conventional cast iron cylinders, we are not able to increase the temperature from a defined level; one reason is that the wear rate on cylinder ring contact will increase excessively. One of the major benefits of using ceramic coating is their ability to withstand in higher temperatures, while having adequate hardness to improve wear rate and reduce friction of coefficient. High temperature wear characteristics between plasma sprayed cylinder liner and piston ring were investigated to find the optimum operating temperature, using a designed wear test stand in lubricated condition. Here we have chosen a single layer Al2O3 - 12wt% TiO2 plasma sprayed on gray cast iron. The thickness of the coating is about 200 micron. Test is conducted with a test stand designed for this purpose which can simulate the real conditions including type of movement, temperature and lubrication, while using the cylindrical geometry of the cylinder liner and piston ring. The mechanism is a reciprocating piston ring on cylinder liner specimen and it can control the temperature up to 300°C. Test specimens are cut from a cylinder bore. Specimens are tested against an standard piston ring. Three set of specimens are tested, at temperatures 250, 150 and 25°C. At each temperature wear rate of a coated specimen and an uncoated one are compared. Wear rate is determined by using a profilemeter for cylinder liner and optical microscope for the ring. This will show the effectiveness the coating. Friction coefficient is monitored during the test, which is also important in investigation on the wear characteristic. SEM photos obtained from the worn surface show that mild wear and polishing to be the major wear mechanism in this system. The results show major difference between two conditions in higher temperatures. Generally the coefficient of friction is reduced in ceramic coated specimens. Using plasma spray ceramic coating shows improvement in the wear characteristic of ring cylinder contact
  9. Keywords:
  10. Ceramic Coating ; Plasma Spraying ; Tribological Properties ; Friction Coefficient ; Wear Test

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