Microstructural Characterization of Borided Co-Cr-Mo Alloy

This study involves the effect of boriding powder composition on the microstructure and hardness of a CoCrMo alloy borided in a solid medium using the powder pack method. To investigate the effect of boriding powder composition, two different commercial boriding agents, Ekabor-HM and Ekabor III, were thoroughly mixed with ferrosilicon powders to form the boriding media. The CoCrMo samples were tightly packed with the Ekabor-HM and Ekabor III boriding powders in stainless steel containers to minimize oxidation. The boriding process was carried out under atmospheric conditions for 9 h in an electrical resistance furnace preheated to 1223 K. X-ray diffraction (XRD) analyses revealed that the surfaces of the borided CoCrMo alloys consisted of a bilayer composed of CoB and Co2B phases and also contained minor amounts of CrB, Mo2B5, and Mo2B. The average thickness of the boride layer in the samples borided with Ekabor HM and Ekabor III powders was 28±4.1 μm and 21±2.3 μm, while the average hardness of the boride layer was 1752±5.3 HV0.1 and 1364±3.8 HV0.1, respectively.

Novel boriding technique of low-carbon steel weldments

Boriding is considered one of the essential surface treatments for carbon steels during the last decades. The conventional methods of boriding are subjected to many limitations due to the sophisticated setup and the time-consuming treatment. Therefore, less complex methods and less time consumption are the main research objectives past couple of years. This research suggests an enhanced boriding surface treatment technique for low carbon steel. The advantages of the proposed method include the reduction of boriding process time through the development of new boron rich compounds which consequently eliminates the need of specially designed furnaces. The illustrated outputs reveal promising results without sacrificing the physical properties. The proposed technique was carried out experimentally. Depth of penetration and microhardness were measured and compared with results from previous literature. Some trials have shown 35 µm depth of penetration of boron layer at 30 min treatment time associated with micro-hardness up to 2388 HV.

Research results of solid particle erosion resistance of 20GL steel with boriding

The paper presents the results of experimental studies of solid particle erosion resistance of 20GL structural steel samples with two different variants of surface modification based on the boriding process. Characteristics of modified layers such as depth, composition, microhardness were determined. Tests were carried out according to ASTM G76-13 standard at air-abrasive flow rate of 170 m/s, flow attack angles of 30º and 90°, sample surface temperature of 25ºC. It was found that both considered options of surface modification at an angle of attack of 90 ° flow do not worsen the abrasion resistance of 20GL steel samples, and at flow attack angle of 30 ° increase not less than 8 times. A change in the wear pattern of boriding samples with an increase in the angle of attack from 30° to 90° is noted. As after the boriding process surface embrittlement was observed, the angle of maximum wear for 20GL steel with boriding became equal to 90° in contrast to steel without treatment, where the maximum level of wear is observed at 30°. Thus, the change of fracture type from plastic to brittle was revealed, which should be taken into account in full-scale operation of the treated parts. The obtained results indicate that the process of boriding of pump parts made of 20GL steel will increase their solid particle erosion resistance and extend their overhaul period.

Wear Behavior of Borided Cold-Rolled High Manganese Steel

In this study, a novel high-manganese steel (HMS) was borided at 850, 900 and 950 °C for 2, 4, and 6 h by the pack boriding process. Contrary to previous literature, borided HMS uncommonly exhibited saw-tooth morphology like low alloy steels, and manganese enhanced the boron diffusion. Another striking analysis is that the “egg-shell effect” did not occur. The present study demonstrated the silicon-rich zone for the first time in the literature by EDX mapping. Moreover, the formation mechanism of silicon-rich zones was explained and termed as “compact transfer of silicones (CTS)”. XRD analysis showed the existence of FeB, Fe2B, MnB and SiC phases. The boriding time and temperature increased the thickness of the boride layer from 31.41 μm to 117.65 µm. The hardness of the borided layer ranged from 1120 to 1915 HV0.05. The activation energy of borided HMS was found to be a very low result compared to high alloy steel investigated in the literature. The Daimler-Benz Rockwell-C adhesion test showed that adhesions of borided HMS surfaces are sufficient. The dry sliding wear tests showed that boriding treatment increased the wear resistance of untreated HMS by 5 times. The present study revealed that the boriding process extended the service life of HMS components.

The Influence of Process Parameters on Structure and Phase Composition of Boride Coatings Obtained on X39CrMo17-1 Stainless Steel

The boride coatings are characterized by attractive set of properties: high wear resistance and good high-temperature corrosion. In present research the diffusion boride coatings were obtained on X39CrMo17-1 stainless steel. The pack-boriding process was conducted using commercial Ekabor 2 powder. The influence of time of process on thickness and chemical composition was analysed. The boriding process was conducted in 2, 4, 6 hours at 1000 °C using retort furnace. The obtained coating was characterized by double layer structure and contained the FeB in outer layer and Fe2B in inner layer. The thickness of boride coatings increased with process time. The analysis of obtained results showed that the optimal thickness of coating was obtained during 4-h pack boriding.

Formation of boride layers on a commercially pure Ti surface produced via powder metallurgy

In this study, powder metallurgy was applied in a furnace atmosphere to form titanium boride layers on a commercially pure Ti surface. Experiments were carried out using the solid-state boriding method at 900 °C and 1000°C for 12 h and 24 h. Samples were produced by pressing the commercially pure Ti powders under 870 MPa. The sintering process required by the powder metallurgy method was carried out simultaneously with the boriding process. Thus, the sintering and boriding were performed in one stage. The formation of the boride layer was investigated by field emission scanning electron microscopy, optical-light microscopy, X-ray diffraction, and elemental dispersion spectrometry analyses. In addition, microhardness measurements were performed to examine the effect of the boriding process on hardness. The Vickers microhardness of the boronized surface reached 1773 HV, which was much higher than the 150 HV hardness of the commercially pure Ti substrate. The X-ray diffraction analysis showed that the boriding process had enabled the formation of TiB and TiB2 on the powder metallurgy Ti substrate surface. Consequently, the production of Ti via powder metallurgy is a potentially cost-effective alternative to the conventional method, and the boriding process supplies TiB and TiB2 that provide super-high hardness and excellent wear and corrosion resistance.

Kinetics of the Boride Layers Obtained on AISI 1018 Steel by Considering the Amount of Matter Involved

Boride layers are typically used to combat the wear and corrosion of metals. For this reason, to improve our knowledge of the boriding process, this research studied the effect of the size of the treated material on the kinetics of the growth of the boride layers obtained during a solid diffusion process. The purpose was to elucidate how the layers’ growth kinetics could be affected by the size of the samples since, as the amount of matter increases, the amount of energy necessary to make the process occur also increases. Furthermore, the level of activation energy seems to change as a function of the sample size, although it is considered an intrinsic parameter of each material. Six cylindrical samples with different diameters were exposed to the boriding process for three different exposure times (1.5, 3, and 5 h). The treatment temperatures used were 900, 950, and 1000 °C for each size and duration of treatment. The results show that the layer thickness increased not only as a function of the treatment conditions but also as a function of the sample diameter. The influence of the sample size on the growth kinetics of the boride layers is clear, because the growth rate increased even though the treatment conditions (time and temperature) remained constant.