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One of the promising methods of increasing surface hardness of engineering tools is boronizing. The boronized parts have extreme hardness exceeding 2000 HV, excellent mechanical properties and corrosion resistance. In this study, salt bath boronizing processes were performed on EN-C35E steel substrate in slurry salt bath containing borax, boric acid as boron sources and ferro-silicon as reductant. The process was performed at the temperature of 850º and 950ºC for 2, 4, 6 and 8 hours. Boride layers were examined by optical microscope (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). Mechanical properties of boride layer were characterized with hardness and fracture toughness measurement. Boride layer hardness was measured by knoop indenter under load of 0,5N and fracture toughness of borided surfaces for 950 °C was measured using Vickers indenters with a load of 4N. Metallographic and XRD analysis revealed that single-type Fe 2 B layers were formed on the surface of EN-C35E steel. Depending on boronizing time and temperature, it was found that the hardness of boride layer ranged from 1895-2143 HK 0.05 that is nearly 8 times higher than the steel substrate hardness. It was observed that the fracture toughness of boride layer ranged from 3.60 to 4.20 MPa m 1/2 .

Boronizing, which involves diffusion of boron atoms into steel substrate to form hard iron borides is well known diffusion coating technique. In this study, salt bath boronizing processes were performed on EN-C35E steel substrate in slurry salt bath containing borax, boric acid as boron sources and ferro-silicon as reductant. The process was performed at 850 and 950ºC for 2, 4, 6 and 8 hours. Boride layers were examined by optical microscope (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). Hardness of borides formed on the steel substrate was measured by Knoop indenter under load of 0.5N. Metallographic studies and XRD analysis revealed that single-type Fe 2 B layers were formed. Depending on boronizing time and temperature, it has found that the hardness of boride layer ranged from 1895-2143 HK 0.05 that is nearly 8 times higher than substrate hardness. The thickness of the layer ranged from 25 to 167 µm depending on boronizing time and temperature.

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Biomaterials are used in different parts of human body as replacement implants in medical applications. An implant material should have high biocompatibility, corrosion and wear resistance, and suitable mechanical properties in terms of safety and long-service period. There are only a few biocompatible implant materials: AISI316L stainless steel is one of the materials used in this type of applications. They have relatively poor wear resistance. Boriding being a thermochemical diffusion treatment is one of the processes to improve their wear resistance. Borides are formed by introducing boron atoms by diffusion onto a substrate surface and they are non-oxide ceramics and could be very brittle. The growth kinetics of boride layer is analyzed by measuring depth of layers as a function of boriding time within a temperature range. In this study, the effects of Ekabor-2 bath on formation mechanism and properties of boride layer in thermochemical diffusion boriding of AISI316L stainless steel were investigated. Different temperatures and durations were applied in boriding operations and hardness, optical microscopy, XRD, EPMA and SEM studies were performed to detect the properties of boride layers. It was found that thickness of boride layer increased with increasing temperature and time; the basic phase in the boride layer formed was Fe2B and FeB phase also formed. It was also found that surface hardness values of borided materials increased depending on temperature and time of boriding process; surface hardness values of borided materials are approximately 10 times higher than surface hardness values of non-borided AISI316L stainless steel and formation activation energy of boride layer is 149.3 kjmol-1.