Optimization and Manufacturing Valve Seat Insert of Iron base Alloy for CNG Engines

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Hosseini, Abdolhamid | 2013

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 44373 (07)
University: Sharif University of Technology
Department: Materials Science and Engineering
Advisor(s): Varhram, Naser
Abstract:
Regard to high temperature and using dry fuel in engines with CNG (Compressed Natural Gas), wear problems and instability of valve seat insert (VSI) in these types of engines have been increased. Today some of high alloy steel (consist of Cr,Ni,Co,W,Mo, . . .), Ni-base alloy or Co-base alloy are used in manufacturing VSI. It's clear these materials have high price. In powder metallurgy methods high percentage alloy is used for manufacturing VSI. These are the reasons why casting method for VSI manufacturing has been pleasant to be used.
In this project the cast iron has been used for CNG engine VSI, by adding some elements like Mo,V,W, and Nb. The graphite has been used as solid lubricant in structure, and the matrix is tempered martensite with M7C3 eutectic carbides. Wear and operating test have been done on samples and quality of surface (Rmax) and material stability has been investigated. Tempered martensite matrix with a little remained austenite with M7C3 eutectic carbides (Fe,Mo,Cr,V) and separated carbides TiC,Nbc and WC have the best result
Keywords:
Graphite ; Wear ; Compressed Natural Gas (CNG) ; Valve Seat ; Iron Base Alloy