FRACTURE-TOUGHNESS OF SINTERED METAL-MATRIX COMPOSITES BASED UPON HIGH-SPEED STEELS ENRICHED WITH HARD CERAMIC CARBIDES

The fracture toughness was measured of a sintered high speed steel which contained copper phosphorus to aid sintering and to which had been added either titanium carbide or vanadium carbide particles as a means of improving its wear resistance. Relatively low fracture toughness values were obtained and these were attributed to embrittlement caused by the presence of phosphorus, but the fracture toughness was relatively independent of the presence of any porosity or carbide enrichment. Reductions in bend strength brought about by heat treatment and by the carbide enrichment process were explained by the effects that the carbide additives had on crack initiation and by the changes caused to the fracture toughness of the steel matrix. In spite of the reductions in strength which occurred as a result of introducing ceramic carbide particles into the steel matrix, useful and promising properties were still obtained. (C) 1993 The Institute of Materials.