Study of the relation between hardness, toughness and resistance to wet abrasion in diamond segments with modified compositions

摘要

No diamonds were involved in this investigation, which was designed to measure the mechanical properties of a series of isolated PM matrix alloys, intended to hold diamonds in stone-cutting segments. Having been given the arguably confusing commercial name of "NEXT," the compositions and nominal properties of the alloy powders investigated are listed in Tables 6 and 7. Diamond segments are normally produced by hot pressing, partly to reduce the time during which the diamond may undergo phase change to graphite. However, the good sintering characteristics of Cu/Fe/Co powders suggested that conventional cold pressing and sintering might be a possible alternative. For evaluation, Charpy bars were produced by this method, specimens of each alloy having slightly different final dimensions because of varying shrinkage during sintering. The powders were uniaxially pressed at 600 MPa and sintered in a slightly reducing atmosphere of 95 percent N_2 and 5 percent H_2. Sintering temperature was 820 deg C for NEXT 100 and 300, and 770 deg C for NEXT 200. This contrasted with the sintering cycle suggested by the powder manufacturers, which covered only the hot pressing route.