SINTER-HARDENING RESPONSE OF SINTERED STEEL BASED ON ASTALOY MO AND ITS DIFFUSION BONDED DERIVATIVES

Artikel i vetenskaplig tidskrift, 2014

This study addresses the sinter-hardening response of sintered steel based on Astaloy Mo grade (prealloyed with 1.5 wt.% Mo) and its derivatives Distaloy DH- diffusion bonded with 2 wt.% copper and Distaloy DC- diffusion bonded with 2 wt.% Ni, respectively. Compacts of these powder grades were sintered at 1120°C for 30 minutes and cooled at a rate of 2.5 °C/s within the range of 800 to 300 °C followed by stress relieving at 200 °C for 60 minutes. In order to understand the relation between microstructure and the obtained mechanical properties, tensile testing and metallographic investigations were performed. It is shown that the distribution of the alloying elements as expected has a crucial impact on the microstructure development where regions lean in Cu or Ni become bainitic while regions with Cu or Ni become martensitic. Also, despite of the fact that Cu is more homogeneously distributed into the DH material, while Ni partly remains in Ni-rich regions in the DC material, both alloys show similar sinter-hardenability. The compensating effects by carbon redistribution upon bainite formation and Ni on C activity are supposed to be key factors in this context.