Room temperature hardness of carbide strengthened cast alloys in relation to their carbon content and aging temperature Part 3 – Case of iron alloys

Abstract

Vickers macroindentation was performed on seven cast and aged Fe–30Cr based alloys with carbon contents varying from 0 to 2·0 wt-%. The measured hardness was studied versus the carbon content and the aging temperature (1000, 1100 and 1200°C). The hardness increases with the carbon content, first slowly but much faster when the carbides fraction reaches 30 vol.-%. A hardness of 600 HV or more can then be achieved. For low carbon contents, the hardness increases slower than a law of mixture of the volume fractions and of the hardness of carbides and matrix. This is due to the great difference in hardness between the two phases, which leads to the deformation of the matrix only. Beyond the critical value of 30 vol.-% of carbides, i.e. when the carbon content approaches 2 wt-%, hardness drastically increases since the main role in resistance against indentation is then played by the hard carbides skeleton, which has become continuous enough.