Mechanisms of abrasive wear in the grinding of titanium (TC4) and nickel (K417) alloys

The present investigation was dedicated to elucidate abrasive-wear mechanisms during surface grinding of a titanium alloy (TC4) and a nickel-based superalloy (K417) by using silicon carbide (SiC), alumina (Al2O3), and cubic boron nitride (CBN) wheels. The temperature at the wheel–workpiece contact zone was measured using a workpiece–foil thermocouple. SEM and EDS were used to examine the morphological features of ground workpiece surfaces and worn wheel surfaces. It is shown that the grinding with either SiC or Al2O3 is characterized by the high temperatures reached in the grinding zone since either of them is easily worn during the grinding processes. Along with the presence of high temperatures, strong adhesion was found between the abrasives and workpieces, which might be attributed to the chemical bonding between the abrasives and workpieces at the elevated temperatures. The increasing ductile deformation of both TC4 and K417 at the elevated temperatures may also be a factor. Therefore, the wear of SiC or Al2O3 is both chemical and physical. In the grinding with CBN wheels, however, the wear of abrasive grits is mainly physical since CBN is more stable to higher temperatures. At extremely high temperatures, CBN was found to undergo dislodging prior to being gradually worn. In order to reduce the grinding temperatures, a segmented wheel was incorporated into the grinding with CBN wheels.