1. Liquid-phase laser sintering based on Rapid Prototyping technology can be successfully used on powder steel 3Kh3F12, the structure of which has a high concentration of a low-melting carbide eutectic. No low-melting additives are needed in this case. 2. Optimization of the parameters of the laser fusion of powder steel for the duration of the production process makes it possible to obtain small compact specimens (5 mm in diameter and 30 mm in length). 3. Sintered specimens of steel 3Kh3F12 have a microstructure of ledeburite and martensite with 15% vanadium carbides and 16% residual austenite. 4. Despite the high cooling rates (100–1000°C/sec), multicomponent segregation along grain boundaries is seen in the specimens after the laser treatment.