Tungsten Carbide Buttons Used for DTH Drill – Failure Mode (2/2)

In addition, edge button lost after the failure of the original gage role DTH drill, drill itself will begin to wear occurs, which also shows the life of buttons directly affects DTH drill service life. Related researchers through a lot of experiments summarized two mechanisms carbide abrasive wear of buttons, one is tungsten carbide (WC) and cobalt (Co) subjected to a uniform wear, similar to polishing action phase, another is cobalt (Co) is first removed, and tungsten carbide (WC) particles are pulled and caused scratch; surface fatigue wear caused by tungsten carbide buttons and rock slide occurred relatively arising and produced alternating load; Adhesive wear occurs at the hardness of tungsten carbide ball and rock hardness are approximately equal state, and tungsten carbide buttons have plastic deformation and rock relative motion between the two separated and then bonded to each other, in this process carbide particles are stripped and blemishes.

2. Button Break: In the form of failure to wear mentions the concept of middle button and the edge button so that button break can be divided into the middle button break and the edge button break. Furthermore, the edge button plays a protective effect on the life of the drill DTH greatest impact. Generally, DTH drill bit end faces and buttons oblique angle of 35 °, due to the action of force is mutual, at the time of impact rock drill, eccentric impact occurs, while when the rotary drill bit cutting edge button by friction of rock, two forces together to produce the side teeth of the roots of a certain moment, the force long-term effect of such cycle prone to cracking source internal button, leading edge button fracture. However, the middle button does not produce eccentric impact, which the impact mainly caused by the friction of rock and button produced the bending tensile stress.

3. Button Drop: Button drop and smash is also occurred. The main reasons of tungsten carbide DTH drill buttons drop includes button drill bit not in the same horizontal plane at a fixed time, causing all the balls can not contact with the teeth of rock, the individual button floating ball practice involved, tensile stress wave, and the buttons has been pulled out; DTH drill cuttings by air blowing to wear during operation, resulting in part of the button exposed, thereby reducing the button bit rigid binding force; The last reason is DTH drill button arrangement when the interference does not fit properly, resulting in insufficient fastening force some button loss occurs.