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This investigation examines the possibility of adding niobium (Nb) to the Fe-Cu system in order to obtain, after powder compaction and sintering, a binder material (bonding matrix) with the adequate wear properties needed for the fabrication of diamond impregnated tools for stone cutting. The main objective is the replacement of cobalt (Co) by Nb in the Fe-Cu-Co alloys that are currently used in diamond tools. For this purpose, a comparative study has been conducted on some selected compositions of matrices integrated in cutting discs. Results of diamond impregnated 25wt%Fe-50wt%Cu-25wt%Nb and 25wt%Fe-50wt%Cu-25wt%Co matrices are directly compared because all tests were conducted under similar conditions. Two types of diamonds were used: without coating and Ti-coated. After the hot-pressing cycles, the main mechanical properties of the sintered bodies were evaluated. Cutting tests under real conditions, in Porriño granite, were carried out to compare the performance of the tools. Although the mechanical properties of the matrices with Nb were different from those found in the matrices with Co, the results obtained from the cutting tests have revealed that the tools made of 25wt%Fe-50wt%Cu-25wt%Nb and 25wt%Fe-50wt%Cu-25wt%Co matrices, both with 50/60 mesh diamonds, show quite similar behaviour during the cutting operations, thus indicating that replacement of Co by Nb is a promising route to be followed in the near future.

Most of the alloys used as bonding matrix in diamond tools show a high content of cobalt -which is undesirable due to a series of reasons. In the last decade, some attempts were made towards the reduction of the Co content in these alloys. NEXT100J alloy (50wt%Cu-25wt%Fe-25wt%Co) by Eurotungstene is an example of it.This study aims to characterize the structure, microstructure and some mechanical properties of the NEXT100 -this is an comercial alloy widely used as bonding matrix for diamonds in cutting tools, and the informations about its properties are very scarce in the literature.The NEXT100 powder was hot pressed in a graphite matrix at 35MPa/800 C/3 minutes. It was performed structural and microstructural analyses by x-ray diffraction and scanning electon microscopy, respectivelly. Wear resistance and hardness HRB tests were carried out -these are the most important mechanical tests for a diamond bonding matrix. It was demonstrated that the samples presented good mechanical properties, XRD analysis showed the presence of two phases, Cu (CFC) and the solid solution a-Fe (CCC). Microstructural aspects are high densification, homogeneous distribution of phases, and little presence of pores.

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