| Summary: | 碩士 === 義守大學 === 材料科學與工程學系 === 101 === The alloyed gray cast iron was investigated in changing various silicon content (2.37、2.70 and 3.20wt%) and release the mold in different time (90、110 and 180 seconds) to change the cooling rate. The Ball-on-disk system was used for wear test at sliding distance 100 to 5000m. In order to comparing the wear behavior, the wear loss were measured, and using scanning electron microscope (SEM) to examined the worn surface, cross section of worn surface and worn debris.
The wear behavior of alloyed gray cast iron can be can be divided into three stages. In initial stage, abrasive wear occurred in the matrix or graphite phase, graphite is easy to be towed to the wear surface and provide self-lubricating, lead to no significant wear loss. In second stage, oxide generate and prevent direct metal-to-metal contact between the asperities of the sliding surfaces, and leads to prevent the wear loss increase. In third stage, fatigue crack generate, lead to delaminations wear appeared. The results shown that the flake graphite fraction raise from 9.2% to 11.7%, it was increase with silicon contents from 2.37wt% to 3.20wt%, flake graphite tips were easy to form the cracks by stress concentration, and leads to increase the wear loss from 1.88mg to 3.31mg. In silicon content 2.70wt%, add the mold release time from 90s to 110s, the hardness was decrease from 47.4HRC to 36.3HRC, because of the hardness decrease, the crack was easy to form, lead the wear loss increase from 2.91 to 3.49mg.
To summarize, the wear loss of alloyed gray cast iron was increase with silicon content and mold release time. Alloyed gray cast iron with 2.25wt%Si had better wear resistance at 90 seconds release mold.
|
|---|
