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In this study, the surface of steel tooth drill bits (Ni-Cr-Mo based) was subjected to the solidstate boriding treatment with 10-50 nm particle size Nanoboron powder. Boriding processes was carried out at a constant temperature of 1273 K for 30, 45, 60, 75, 90 and 105 minutes using a solid-state box boriding technique. Borided drill bit samples were characterized by conventional methods (microstructure, microhardness, X-ray diffraction and chemical analysis). Wear behaviour of borided samples was tested at different loads and sliding speeds by a microabrasion experimental set up. Metallographic studies showed that the boride layers have a sawtooth morphology and consist of FeB and Fe 2 B. The thickness and hardness of the boride layer was found to be 35.29 -202.56 μm and, 1300-2333 HV 0.1 , respectively, depending on the duration time. The wear resistance of borided samples increased significantly due to the increase in surface hardness and lubricating effect both of which were caused by boriding process.Grooving wear mechanism prevailed in borided samples, while that of bare steel tooth drill bits (STDB) was grooving, rolling and mixed. INTRODUCTIONDrilling is the operation of opening holes in the earth's surface with the help of a drill bit.Drilling systems are divided in two ones as rotary and percussion. Although the rotary system is preferred in deep drilling, both systems have their advantages and disadvantages. In both systems, the drilling performance usually determines the cost of drilling. The drilling performance depends on the drill bit selection as well as the use of the drill bit. Significant cost reductions are ensured through choosing a reliable drill bit (Moore (1); Grimes, et. al. (2); Bobo(3)).The rotational speed of the drill is as effective as the drill selection on the drilling costs and service life of the drill bits. Rotation speed is recommended as 30-40 rev/min in lower surface drillability, 60-120 rev/min with the ability to drill in surface and 70-140 rev/min in the surface of higher ability to drill. In very soft rock rotation speed can be 200-250 rev/min (Moore (1); Cummins (4)).To increase the drilling rate, compression force should be kept constant and the rotational speed must be increased. However, increasing the rotational speed results in an increase in the temperature of the drill bit surface and it accelerates the corrosion and wear (Moore (1); Praillet (5)). Modifications on these materials should be made to ensure the resistance of the drill bit to high temperature conditions.In the improvement of the mechanical characteristics of the steel materials, the most convenient and economical way is surface hardening. Surface hardening methods provide Downloaded by [University of Leeds] at 14:07 05 June 2016 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 4material surfaces with harder, strong, and abrasion-resistant structures; and a more energyabsorbent inner structure which provides toughness (Ulutan, et. al. (6)). Boriding heat treatment is a commonly used hardening process (ġen, et. ...

A dental crown material, Nickel-Chrome-Molybdenum alloy, is manufactured using precision casting method from a polyurethane foam model in a regular and open-pore form, as a hard tissue implant for orthopedic applications. The samples produced have 10, 20, and 30 (±3) pores per inch of pore densities and 0.0008, 0.0017, and 0.0027 g/mm3densities, respectively. Samples were implanted in six dogs and observed for a period of two, four, and six months for the histopathological examinations. The dogs were examined radiologically in 15-day intervals and clinically in certain intervals. The implants were taken out with surrounding tissue at the end of these periods. Implants and surrounding tissues were examined histopathologically in terms of biocompatibility. As a result, it is seen that new bone tissue was formed, in pores of the porous implant at the head of the tibia in dogs implanted. Any pathology, inflammation, and reaction in old and new tissues were not observed. It was concluded that a dental alloy (Ni-Cr-Mo alloy) could also be used as a biocompatible hard tissue implant material for orthopedics.

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