Comparison of material properties in as-cast and austempered cast irons with three different graphite morphologies

• Three cast irons with different graphite morphologies were austempered in order to investigate how some important material properties are affected. The cast irons had similar chemical compositions so valid comparisons could be made between morphologies and between as-cast and austempered samples. The cast irons were austenitized for 2h at 900°C and austempered at 350°C for five different times, resulting in coarse ferrite needles. Microstructure, hardness, scuffing resistance, ultimate tensile strength (UTS) in bending and thermal properties was investigated for both as-cast and austempered samples. The hardness increased by about 25% after 110 min austempering while the thermal conductivity dropped about 30%, for all three morphologies. Scuffing resistance increased significantly when austempering lamellar graphite cast iron but was slightly reduced for both the compacted and nodular graphite morphologies. After 110 min austempering, the ultimate tensile strength was reduced for the lamellar and compacted samples, but was slightly increased for the nodular morphology.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Austempering

Ausferrite

Lamellar graphite cast iron

Compacted graphite cast iron

Nodular graphite cast iron

Vickers hardness

Scuffing resistance

UTS

Thermal conductivity

Materials science

Teknisk materialvetenskap

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