Recipient of the 2017 Outstanding Master's Thesis Award - Second Place.
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Thesis (UNI Access Only)
Diesel motor--Cylinder heads--Materials; Diesel motor--Technological innovations; Iron alloys--Properties;
The tightly regulated EPA emission requirements and the customer demand for more power and torque at better value has been forcing the heavy duty diesel engine industry to push the limits of material capabilities on cylinder head component designs while competing for market share. This research was conducted to develop a gray iron alloy material for a cylinder head casting that was capable of 10,000 thermal fatigue cycles running at temperatures of 400°C and above without failure. Likewise, the new highly alloyed material needed to limit manufacturing and machining cost increases to 25% of the current production gray cast iron material and maintain a defect rate of less than 10% in production to preserve consumer value. Based on historical literature and previous material developments by John Deere in the early 1990’s, the thermomechanical fatigue properties of the standard gray cast iron material was increased with additions of molybdenum with minor amounts of tin and chromium while restricting the nickel to residual amounts. A design of experiments (DOE) study was used to determine the most cost effective casting approach to reduce the casting defects that traditionally plagued castings when these additional alloying elements are applied to the gray iron composition. New inoculation formulas, chill techniques, and exothermic risers were all used within the parameters of the DOE for defect elimination. In the end, using the new alloy additions and successful casting techniques, the fatigue life capability of the cylinder head design had effectively been doubled at the elevated temperatures and operating condition requirements with an acceptable defect scrap rate. Although the monetary increases for the new high alloy gray cast iron were greater than desired, the enhanced durability gains to the thermo-mechanical fatigue life of the cylinder head was deemed more valuable to the customer base seeking a higher power engine even at a premium cost.
Date of Award
Master of Science
Department of Technology
Scott R. Giese, Chair
1 PDF file (x, 105 pages)
© 2015 Jeremy M. Kessens
Kessens, Jeremy M., "Development of a gray iron alloy for improved thermo-mechanical fatigue life in a cylinder head for diesel engine applications" (2015). Electronic Theses and Dissertations. 212.