In tests of the effect of isothermal sintering time on the density of specimens sintered at different temperatures (Fig. 1) the expected high-rate densification at firs stage was observed. This is caused by the accelerated regrouping of particles which occurs when liquid phase appears at interparticle contacts as a result of the formation of a low-melting
eutectic in the Ni − B system [9]. The most rapid porosity decrease occurs in the initial stage of the process: in the first 5-15 min. Later, the densification rate decreases, and after 60 min holding at sintering temperature the curve ρ = ρ(τ) becomes flat, i.e., densification of the material practically stops. The shrinkage curves at 1180 and 1200°C are similar in shape but the absolute value of shrinkage is substantially higher in the latter.