WC-20%Co合金およびこれにTaCを添加した合金の性質

Abstract

The purpose of this report is to examine some properties of WC-20%Co and WC-5%TaC-20%Co alloys as a function of the carbon content, and to compare their properties with WC-(TaC)-10%Co alloys already reported(1)∼(9). Two series of alloys, viz., WC-20%Co and WC-5%TaC-20%Co with various carbon contents in the two or three-phase (γ+carbides) range, were prepared by vacuum-sintering at 1375°C for 1 hr. The grain size of carbides in all the alloys was controlled to be approximately the same through some treatments before sintering. The main results are as follows: (1) A maximum value of the transverse-rupture strength is obtained at the low carbon alloys in the two or three-phase range. However, in the case of 10% alloys, the maximum value is at the high carbon alloys. (2) The addition of TaC up to 5% does not decrease the transverse-rupture strength, but the 3%TaC addition to 10%Co alloys decreases its value. (3) The width of the two or three-phase range is approximately two times as wide as that of 10%Co alloys. (4) The TaC addition increases the hardness but decreases the density. (5) The γ-phase contains almost no TaC. (6) The aging phenomena accompanied by the Co3W type precipitation is also ascertained in these alloys, but there is the difference that the hardness and the coercive force of these alloys increase after aging.