A method of strengthening the matrix of a high-speed steel for forming a composite tool material by super-deep penetration of reinforcing particles into and through the matrix of the tool material. The particles interact with the matrix in the form of a high-speed jet generated and energized by an explosion of an explosive material that contains the premixed powdered components of the working medium composed of particles of a hard material and ductile metal, and if necessary, with an addition of a process liquid. The particles of the working medium material have dimensions ranging from 1 to 100 μm. The jet has a pulsating nature with the velocity in the range of 200 to 600 m/sec and a temperature in the range 100 to 2000° C. As a result of strengthening, the steel matrix is reinforced by elongated zones of the working material particles which are oriented in the direction of the jet and occupy less than 1 vol. % of the matrix material, while less than 10 vol. % is occupied by the zones of the matrix restructured as a result of interaction with the particles of the super-high velocity jet.