A cobalt-rich wear resistant and corrosion resistant alloy comprises in weight %, 0.5 to 1.2% C, 0.6 to 2.1% Si, 17 to 24% Cr, 27 to 38.5% Fe, 1.4 to 20% W, 3.8 to 9.7% Mo, less than 1% Ni and balance Co. A preferred cobalt-rich alloy comprises in weight %, 0.5 to 0.9 C, 0.75 to 1.15% Si, 17.5 to 20.5 Cr, 27.0 to 32.0 Fe, 12.5 to 16.5 W, 6.25 to 8.25 Mo, 0.45 to 1.00 Ni and balance Co. The alloy preferably has a microstructure free of primary carbides and comprises up to about 50% by volume eutectic reaction phases in a solid solution matrix. The solid solution matrix is an αFe-αCo face-centered cubic solution with W, Cr and Mo as solute elements and the eutectic reaction products comprise a (Co,Cr)7(W,Mo)6 phase and an αFe-αCo phase. The alloy is useful as a valve seat insert for internal combustion engines such as diesel engines.