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Effect of Sintering Atmosphere on Mechanical Properties of Heat Treated PM Valve Seat Insert Produced by Copper Infiltration

  • : Mehdizadeh Lima, M1
  • : 1Iran Powder Metallurgy Complex
  • : PDF Download
  • : 2012

Abstract

Valve seat inserts (VSIs) are used to improve the performance of Aluminum block engines through the addition of a higher performance steel insert. PM has proven to be the best solution for valve seat inserts through the combination of unique wear resistant and high thermal conductivity materials, and near net shape geometry. VSI with complicated chemical composition (based on MS40Cu standard) in the presence of Cr, Ni, Mo, S, Cu and C has complicated sintering behavior and therefore is selected as a case study to be investigated. The presence of nickel in the alloy composition stabilizes austenite phase. This stabilization is also affected by sintering atmosphere. Carbon-rich atmospheres such as endothermic increase the possibility of stable austenite and thus reduce the mechanical properties like hardness and radial crushing strength after heat treatment. In this research, the effects of endothermic and ammonia cracked sintering atmospheres on microstructures and mechanical properties of sintered- heat treated and tempered VSIs were studied. The results show that the microstructures and mechanical properties of tempered samples are strongly affected by sintering atmosphere.
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