నైరూప్య

Thermal expansion of cobalt-based, nickel-based and iron-based cast alloys reinforced by chromium carbides

Patrice Berthod, Lionel Aranda

Six 30wt.%Cr-containing alloys reinforced by chromiumcarbides, two ones based on cobalt, two ones based on nickel and two other ones based on iron, were elaborated by foundry way and studied in thermal expansion between 100°C and 1200°C, for two microstructure orientations favoured by special cutting. The heating parts, isothermal parts and cooling parts were quantitatively analysed. The main global differences of thermal expansion were obtained between the alloys based on Co or Ni (high expansion) and the ferritic Fe-based alloys (low expansion). A higher amount of carbon or carbides generally led to slower dilatations and to enhance attenuation of expansion due to crystallographic changes of matrix. This also leads to a compressive deformation of matrix at the highest temperatures, due to the differential expansion between the two phases from room temperature and these high temperatures. Negative permanent deformations were thus obtained for the alloys.