The influence of carbon on the layer formation during Interdiffusion of Mo and Fe

Experiments have been carried out between 800 and 1300° C with diffusion couples prepared from iron containing 0·09 wt.-% carbon and pure molybdenum. At all annealing temperatures an η carbide, Mo ₃ Fe ₃ C, is formed with a very narrow homogeneity range, viz., ∼ 3 at.-% Fe. The formation of the carbide is very fast, but stops at a certain layer thickness. During heating at temperatures from 800 to 1000° C a two-phase layer is also formed, probably consisting of Mo ₂ C and the η carbide. The solid-solution layer of Mo in Fe grows parabolically above 1000° C. Below 1000° C it reaches the equilibrium concentration only after the disappearance of the two-phase layer. The diffusion behaviour in this system is compared with the results obtained in the Mo–Ni–C system.