Study On A New Type Of Maceration Alloys With Low-Cost And High-Property Used In PDC Bits

As polycrystalline diamond cutter (PDC) well bit, its service life, shearing resistance and abrasive resistance depend on its maceration alloy's quality. Copper alloys have been the most widely used for maceration alloy of PDC well bit, because of its excellent wetting property, mechanical properties and corrosion resistance. Currently, Cu-Ni-Mn maceration alloys are widely used, but this kind of alloy has high cost, low tensile-strength, low fluidity property and high melting point. Therefore, the research on maceration alloy of PDC well bits is done by forcing on new type and low price copper alloys.Based on this background, casting processing was adopted to prepare series of Cu-Ni-Sn-Mn-Fe alloys and pressureless infiltration technology was adopted to prepare series of WCp/Copper alloy matrix materials. In this dissertation, by means of metalloscopy, SEM, TEM, energy spectrum and the measurement of wear and hardness, the microstructure and properties of maceration alloys and composites are studied. It is found as follows:(1) The cast structures of all Cu-Ni-Sn-Mn-Fe maceration alloys have three zones: Treelike crystal is inner layer consisted of Cu-Ni solid solution with rich Cu and Ni. Outer layer of treelike crystal is {Cu, Sn} phase with rich Sn. These alloys exist serious Sn segregation in the as cast structure by macro-observation. If these alloys need to undergo cold-working and hot-working treatment, they must be heat treated in order to eliminate Sn segregation.(2) A little Fe added in Cu-Ni-Sn-Mn alloys made mechanical properties increase, because doped Fe refined the microstructure and the gain. However, when the Fe content reaches in some value (5% Fe), the action was not obvious.(3) After 400℃aging four hours, there are much moreα-Cu phase formed in A5 alloy. And its strength and hardness were stronger than that of casting alloy, but its elongation percentage and plasticity were lower than that of as cast alloy.(4) In WC_p/Cu-Ni-Sn-Mn-Fe composites, almost skeleton particles WC were able to be soaked by copper liquid, and had a strong interface bonding with copper matrix. At the same time, there were the interface solution and mass interdiffusion of Fe, Cu, W and C elements between part of WC particle and copper maceration alloy, and Fe₃W₃C compound and Cu_0.4W_0.6 compound were formed.(5) WC particle were main wear resistant phase in matrix materials, because of the strong strength and malleability of copper matrix alloys. Therefore, series of matrix materials have excellent wear resistances. The wear loss of copper maceration alloys are mainly caused by plastic deformation,ploughing and spalling properties, and the wear loss of WC particle are mainly caused by micro-cutting and brittle micro-peeling.