Microstructural and electrochemical study of a brazed WC based metal matrix composite obtained by infiltration process

In the present work, a metal matrix composite (MMC) was produced by the infiltration of a Ni-based bronze (74.4 wt.% Cu. 15.8 wt.% Sn, 3.8 wt.% Mn and 5.5 wt.% Ni) into a mixture of WC/W2C, Cu and Mn powder. The obtained piece was subsequently assembled to the WC-Co cermet of a polycrystalline diamond compact (PDC) insert. The joint was performed by oxyacetylene brazing process using an Ag based alloy (49 wt.% Ag, 23 wt.% Zn, 16 wt.% Cu 7.5 wt.% Mn, 4.5 wt.% Ni) as the brazing filler metal (BFM). The microstructure of the resulting system was studied by means of Scanning Electron Microscopy and X-Ray diffraction. Of special interest is the MMC and MMC/BFM interface, where the formation of an inter-diffusion zone is observed with the presence of new phases such as, AgMn19, Mn-Zn and Cu-Zn, that enhanced the bonding of the MMC to the WC-Co cermet. Additionally, the electrochemical behavior of the interface was studied in 0.5 M NaOH solution, followed by the analysis of the electrolytes by Inductively Coupled Plasma Atomic Emission Spectrometry. The results highlight an uneven dissolution of the constituent phases at the MMC/BFM interface due to localized corrosion processes and galvanic interactions occurring between phases of different composition.