EFFECT OF CERAMIC PARTICLES ON THE MECHANICAL-PROPERTIES OF M3 2 HIGH-SPEED STEEL/

New wear resistant materials were developed by adding TiC (6, 16 and 4 2 mu m), TiN (7 and 12 mu m) and TiO2 (12 mu m) particles to AISI M3/2 high speed steel powder containing copper-phosphide and graphite in o rder to obtain composite mixtures sinterable in the temperature range 1140-1170 degrees C. This work presents the effects of the ceramic par ticles on hardness, bend strength and fracture toughness of the compos ites, as compared to those of the base material. Since ceramic particl es acted as crack initiators and reduced bend strength, additions of f iner particle sizes resulted in a higher average of bend strength valu es (1.35G.Pa) than in composites containing coarser additions (1.17GPa ). The average bend strength of the base material was 1.40GPa. No sign ificant increase in hardness was obtained by adding the hard particles to the base material. Hardening and tempering caused a slight hardnes s increase and could therefore be beneficial to wear resistance. The c omposites containing TiO2 however were very porous and the hardness of the particles decreased significantly due to their interaction with t he matrix, making these additions unsuitable. Fracture toughness was n ot affected significantly by the presence of the ceramic particles but , heat treatment caused a decrease in fracture toughness from an avera ge value of 16.5MPa m(1/2) in the as sintered condition to 13MPa m(1/2 ) after hardening and tempering.