South-West State University (Kursk, Russia):

Gorozhankin V. V., e-mail: svarka-kstu@mail.ru

Kolmykov V. I., Professor, Doctor of Engineering Sciences

Romanenko D. N., Acting Head of a Chair, Candidate of Engineering Sciences

Nowadays, roller bits of various designs and sizes are widely applied for the wells drilling in hard rocks. Their basic disadvantage is small longevity, substantiated by extremely hard work conditions. Increasing of longevity of roller drill bits by increasing of abrasive wear-resistance of their operating devices is an urgent task. Significant wear of rollers' frames is connected with the fact that properties of their materials are insufficient for effective resistance to strains and abrasive effect of drill cuttings. The authors have carried out the works, directed on increasing of abrasive wear-resistance of steel products by their carbon saturation to high concentrations (close to eutectic). As a result, diffusion layers, saturated with large amount of solid phase (cementite) inclusions are formed on the surface. Such layers provide very high abrasive wear-resistance. Carbonitriding was carried out with the temperature of 850°C during 6 hours. As a result, diffusion layers with 0.7-1 mm depth with large amount of carbonitrides were obtained on the rollers' surface. Thereupon, carbonitrided frames of rollers were annealed with the temperature of 880°C (for the core) in oil and were tempered with the temperature of 180°C during 2 hours. After the processing, solidity of work surfaces of rollers reached the HRC of 66- 68. Reinforcing elements were pressed in carbonitrided frames. At the same time, bearing seating positions were grounded according to the standard technology. Surface carbonitriding hardening of operating devices of button roller bits in paste-like carburizer made it possible to increase their longevity by 2 times and more. At the same time, there were no slipping out of hardalloyed picks from roller's frame, and used bits were sorted in connection with wear and cracking of solid-alloy reinforcing elements.