Fabrication and testing of Al–SiCp composite poppet valve guides

Abstract

Composite materials are replacing the materials used in various fields and are the candidate materials for future growth. Metal matrix composites are the class of composite materials finding vast applications in automotive, aircraft, defense, sports, and appliance industries. In the present work, Al–SiCp composites with 5–30 wt.% of SiC particulates were fabricated using powder metallurgy as well as casting processes. Mechanical alloying of aluminum and SiC particles was done prior to compaction so as to enhance the properties of the fabricated powder metal components. A custom built sliding valve guide wear test rig was fabricated to simulate the valve stem/guide wear under cold start condition of an engine by reciprocation of a valve stem under different imposed loads, against a stationary poppet valve guide. The hardness and radial crushing load was measured for the Al–SiCp composite poppet valve guides and were found better than the cast iron poppet valve guides presently used in engines. The wear test of the poppet valve guides was done using valve guide wear test rig, which revealed that the Al-20 wt.% SiCp and Al-30 wt.% SiCp composite poppet valve guides have higher wear resistance than the cast iron poppet valve guides. The hardness, radial crushing load, and wear resistance of Al–SiCp composite poppet valve guides were found to increase with increase in weight percent of SiCp. The microstructural analysis of the cast and PM Al–SiCp composites was also done using scanning electron microscope. Finite element analysis of the Al–SiCp composite poppet valve guide was also done using Ansys software, which supports the successful implementation of the Al–SiCp composite poppet valve guides for automobiles.