Experimental investigations on multi-material compounds based on rare earths. Using liquid phase sintering and spontaneous infiltration

Abstract

Little information is published on the hardness and corrosion resistance properties of WC-Mn-Cu-Ni alloys infiltrated by an NdPrFeB alloy. Is iron-neodymium-praseodymium inter-metallic compound a desirable choice for a binder for liquid sintering or spontaneous infiltration at high temperatures? Also, is it an opportunity to study the effect of the particle size (d < 30 μm) and the percentage of addition (<5%) of neodymium and praseodymium on the mechanical and electrochemical properties of the composite WC-Cu-Ni-Mn/binder? These inter-metallic composites associating elements of different sizes and electronegativities make it possible to have metallic bonds, but also localized interactions, of the covalent type, between metals and semi-metallic element. The influence of the mechanisms of dissolution and progressive precipitation intervening in the process of densification in the liquid phase allows for obtaining micro-hardness with a value of 1580 HV0.3 and a relative density of 0.798. The micrographs reveal additional information concerning the strong chemical activity of Nd and Pr. The advantage of using the NdPrFe alloy is to take advantage of both the qualities of each element via the coupling of the conduction electrons of the two elements. The behavior of the composite sample in an aggressive (1 M NaOH) medium was examined. Electrochemical parameters determined from Tafel lines show a significant diminution of Icorr when a grain size decreases. For the sample elaborated by spontaneous infiltration the polarization resistance increases to 3686 Ωcm2 and the addition of 4–5 wt% of rare earth (RE) is recommended. In relations to their composition and hardness, we can consider these materials as candidates for magnetic drilling tools.