低コストFe – B とFe の混合粉末放電焼結における挙動とそれらの特性

Abstract

Spark sintering behaviors on mixed powders of Fe – B and Fe with low cost were investigated to develop the hard materials as substitution of WC – Co alloys. The cheap powders with mean composition of Fe – 19.1 wt% B consisting of mixed phases of B, FeB, Fe2B and Fe were ball-milled for crushing the particles with 45 µm. The ball milled Fe – B powders with 10 µm were 0, 10 and 50 vol% Fe added (hereafter called, 100, 90 and 50FeB, respectively). The spark sintering technique was utilized to fabricate ubiquitously hard-materials compacts. The promising maximum temperatures in sintering were defined on three compacts on the basis of the optimization of their Rockwell hardness and relative density. Rockwell hardness number on C scale was changed 66 to 71 depending on Fe contents on three compacts with the densities of 92 − 97 %, and the value of 100FeB compact was the same as that of WC – 7.8Co. The 100, 90 and 50FeB compacts showed the fracture strain of 0.32, 0.43 and 0.53 %, or fracture stress of 345, 435 and 447 MPa, respectively, in three points bending tests at 293 K. The fracture stress and strain were 5 − 17 % decreased and 7 − 9 % increased, respectively, on three points bended samples at 773 K, compared with those at 293 K.