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Test Methodology and Wear Characteristics of Material at Subzero Temperatures

Kazerani, Vessal | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44181 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farrahi, Gholamhossein
  7. Abstract:
  8. Components in cryogenic milieu with relative motion, like seals and pumps cannot be lubricated by using oils or other lubricants. Therefore materials wear in cryogenic condition is a great concern. To earn valid data about the wear properties of common and super useful material in cryogenic tribosystems, reconstruction wear test apparatus at cryogenic temperature is needed. Investigations on metal-metal couple show that austenitic stainless steels have favorable and auspicious sliding properties at cryogenic temperature. This persuades us to survey the wear parameter of these prolific materials like austenitic stainless steels specifically. This research provides the wear parameters of austenitic stainless steel AISI type 304, AISI type 316, AISI type 321 and AISI type 420 in cryogenic environment. For this purpose two sets of test environment are prepared, room temperature (273K) and 77K with the sample immersed in LN2 using designed Pin-On-Disk cryogenic simulator. Specimens are submerged in hexane for overnight to clean surfaces from any foreign contaminant. Disks material is mentioned type of austenitic stainless steel and pin is bearing steel SAE 52100. Test is chosen to have 2 m/s sliding speed and pin normal force, 10N. Friction coefficient is recorded via a designed computer data logger during tests. Test results show reduction in friction coefficient and lower wear rate in cryogenic environment. Better wear resistance properties is achieved, because austenitic stainless steels have higher mechanical strength in cryogenic condition and the forming of nitride layer at worn surfaces which may enhances slipping of pin on the specimen. The wear rate in experiments reported to be approximately 4 – 10 (mm3/Nm). Like friction coefficient, the same trend has been observed on wear rate between specimen in room temperature and cryogenic condition. The major mechanism of wear is severe abrasion in room temperature, by considering SEM micrographs of worn surfaces. In averse, mild abrasive wear mechanism is observed in specimens tested under the cryogenic condition
  9. Keywords:
  10. Wear Properties ; Friction Coefficient ; Wear Test ; Cryogenic Environment

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