Performance Test And Modification Application Of Iron - Based Water Atomized Pre - Alloy Powders For Diamond Tools

Diamond tools are widely used in many applications such as aerospace,machining,construction,etc.Among them,metal bond diamond products are the most consumed type of tools.Sharpness and service life are the main performance indexes of diamond tools,and sharpness is the primary criteria.As a cutting working element,artificial diamond has formed a series of stable product after decades of development,and it is no longer the main factor restricting the performance of diamond tools,thus,as a binding agent,metal powder has become the primary factor affecting and restricting the properties of diamond tools.At present,iron-based binders are the most consumed products,and high-performance iron-based binder powders are also the development trend and focus of the global diamond product industry in the future.Water-atomized iron-based pre-alloyed powder has been developed into a kind of binder with the largest consumption in the domestic market.It has many outstanding cost-effective advantages,but also exists some application obstacles.The prominent problem is the sharpness reduction caused by the higher wear resistance of the coarsening matrix which results from the sintered amalgamated particles,and this is a common difficulty faced by the diamond manufacturers.With enough comprehensive mechanical properties of matrix to ensure sufficient holding force to diamond,one of the effective technical ways to solve the problem is to reduce the abrasiveness of the matrix by refining its microstructure via controlling the growth of the grains,thus,improving the self-sharpening ability of the matrix,furthermore,increasing the protrusion height of diamond gritSystematic measurements and analyses on the basic physical/chemical and mechanical properties of three kind of iron-based water atomized pre-alloyed powders were carried out in this paper,including the elemental Fe-based,Fe-Cu-Sn three-component and Fe-Cu-Ni-Sn four-component powders,with the oxygen content of less than 3000ppm,the bulk density of 2.6?3.3 g/cm3,2.8?3.3 g/cm3 and 2.8?3.6 g/cm3 respectively,the particle size D50 of 16?20? m,13?18 u m and 15?20 u m respectively,the sintering densities of higher more than 95%,the bending strength of 1100?1400 MPa,1000?1200 MPa and 1500?1700 MPa respectively,and the hardness of 95?99 HRB,106?109 HRB and 105?110 HRB respectively.At the same time,the changes of the above-mentioned mechanical performance of these powders were also tested at different sintering temperatures.The structural characteristics of the sintering fracture were systematically analyzed using SEM technology.The functional assembly application of the pre-alloyed powders and ultra-fine carbides(Cr3C2,Mo2C)were designed according to the sintering and microstructure characteristics of these powders.The results of systematic experiments show that the ultra-fine carbides can significantly refine the sintered matrix structure and improve its wettability to diamond.When the carbides addition less than 3wt%,the mechanical properties of these pre-alloyed powders,such as the sintering density,bending strength and hardness do not change much,and when the addition amount exceeds 3wt%,the strength of the matrix decreases significantly with increasing the addition ratio of the carbides,thus,reducing the holding force of the matrix to diamond.The experiment results also show that,under the condition of not reducing the mechanical properties of the sintered body(without reducing the holding force of the sintered body to diamond),the ultra-fine carbides dispersing in the particles can hinder the coalescence of the grains to refine the matrix structure and weaken the interfacial bonding strength between the metal powder particles,thus weakening the wear resistance of the sintered body,and thereby improving the sharpness of the diamond tool.The comprehensive effect of superfine carbide Cr3C2 is better than Mo2C.Small and medium size granite saw blades were prepared by using three iron-based pre-alloyed powders with addition of 3wt%Cr3C2 for cutting test,and their sharpness increase more than 15%comparing with those of without Cr3C2.The corresponding results demonstrate the effectiveness of a new wear adjustment mechanism to improve the sharpness of the diamond tool through the method of refining the matrix structure and changing the binding force of grain boundaries to appropriately weakening the wearability of matrix.