800°C isothermal section of the Co–Cr–Mo–Si quaternary system

Abstract The 800°C isothermal section of the Co–Cr–Mo–Si quaternary system with the Co content fixed at 70 at.% and different contents of Cr, Mo and Si was determined by means of X-ray diffraction and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Twelve different phase regions could be identified; one of them being a wide (Co) + Co 3 Mo 2 Si phase field, but only one four-phase region consisting of (Co) + Co 3 Mo +Co 7 Mo 6 + Co 3 Mo 2 Si was experimentally confirmed. The measured solubility of Si in the Co 3 Mo phase is rather limited but could reach up to 15.1 at.% in Co 7 Mo 6 . The solubility of Cr in Co 3 Mo and Co 7 Mo 6 was measured to be as high as 13.4 and 23.3 at.%, respectively, and the maximum solubility of Cr in (Co), αCo 2 Si and Co 3 Mo 2 Si could reach 26.9, 5.6 and 12.5 at.%, respectively.