Microstructural and mechanical characterisation of composite materials consisting of M3/2 high speed steel reinforced with niobium carbides

Fully dense composite materials of M3/2 tool steel reinforced with 5 and 8 vol.-% of niobium carbide were developed using the powder metallurgy route. The consolidated materials exhibited a fine and uniform microstructure consisting of a fine dispersion of carbide particles in a matrix of ferrite/martensite. The 0·2% yield strength up to 600°C was evaluated in compression. The slight increase observed after reinforcement by NbC particles in as hipped materials suggests that the martensite has the major contribution to the strength. After tempering, the reinforced materials showed a moderate increase in yield stress at room temperature with respect to the unreinforced M3/2. This increase is attributed to reinforcement mechanisms associated with niobium carbide. PM/1175