Effect of different acid corrosion reagents on de-cobalt effect and performance of PDC at room temperature

In this study, we investigated the effects of four different acid reagents, sulfuric acid, compound acid, phosphoric acid and Lewis acid-FeCl3, on the depth of Co depletion layer, thermal stability and bending strength of poly-crystalline diamond compacts (PDC) at room temperature. The results show that the thermal stability and bending strength of PDC after soaking in different acid corrosion reagents are closely related to the acid-etching effect, especially the depth of Co depletion layer. Sulfuric acid has the best effect of removing cobalt at room temperature. After soaking for 48 h, the depth of Co depletion layer reached 140 um from the surface. Its initial graphitization temperature was 850 degrees C, and then increased 130 degrees C with treatment. The bending strength of the PDC was significantly reduced after removing Co from PDC. The larger the depth of Co depletion layer, the lower the bending strength.