Wear properties of shock-consolidated amorphous and microcrystalline Ni-38 wt % Mo−8 wt % Cr-1. 5 wt % B alloy powders

Abstract

Powder flakes prepared from 50 fim thick melt-spun ribbons of Markomet 1064 (Ni 52 . 5 Mo 3g Cr 8 Bj 5 wt %) were shock consolidated in the unannealed and annealed condition. The unannealed powder flakes (microhardness 933 kg/mm 2 ) are amorphous while flakes annealed at 900 °C for 2 h have a fee crystal structure, with a microcrystalline grain size of 0.3 [im and microhardness of 800 kg/mm 2 . The shock-consolidated amorphous powder compact (~250 kJ/kg shock energy) shows no crystal peaks in an x-ray diffractometer scan. Compacts of annealed powder (400-600 kJ/kg shock energies) contain amorphous material (18%-21%), which was rapidly quenched from the melt formed at interparticle regions during the consolidation process. The microhardness of the amorphous interparticle material is 1100 kg/mm 2 . Wear properties of the compacts measured in the low velocity friction apparatus (LVFA) pin-on-disk tests show low average friction values (~0.03). The 60 h cumulative wear appears to correlate with the energy of shock compaction rather than the metallic glass content. The Falex ring-on-block test also showed that both the Markomet amorphous compact and the compact containing a mixture of amorphous and microcrystalline phases performed almost equally and wore half as much as the base-line SAE-01 steel-polished sample.