Papers by Keyword: Boriding

Abstract: Boriding is a thermochemical treatment that can be applied to improve the mechanical and chemical properties of steels by surface modification while stilling adequate substrate properties. This kind of treatment is widely used to protect the degradation of the mechanical parts’ surface against wear. The boride atoms introduced into the steel can produce a hard metallic compound formed by diffusion and precipitation. The present study has been conducted in order to obtain an iron borides layer on two types of steel substrates 16NC6 and 20MC5 by using a powder consisting of B4C, NaBF4 and, SiC. The solid boriding treatment was carried out in an electric furnace heated to 950°C for three holding times of 2h, 4h and, 6h. The present research work focuses an the effect studying of holding time as a parameter on the thickness, structure, morphology, and hardness of layers obtained on low carbon steels by the case boriding. As confirmed by structure and microstructure characterization, the hard boride layers produced form two phases of FeB and Fe2B.

Abstract: Diffusion treatments offer possibilities to enhance the performance and the service lifetime of hot forging tools. In combination with coating after nitriding, the surface layer hardness can be further increased. Within the scope of this study, a surface layer hardness above 2,000 HV0.005 was determined for borided or DLC (diamond-like carbon) coated surface layers. An increased surface layer hardness improves the abrasive wear resistance of forging dies. Furthermore, the plastic deformation of thermally softened forging die areas can be reduced. Beside these desirable effects, the ductility of diffusion treated or coated near surface layers is reduced and thermomechanical cracks are promoted. Therefore, additional approaches were developed to improve the thermomechanical crack behaviour of forging dies. Patterned plasmanitriding by the use of coverages to prevent areas from nitrogen diffusion, new combination processes of plasmanitrocarburizing (PNC) followed by plasmanitriding (PN) and the innovative boriding were investigated on different abstraction levels. A system of several testing rigs was set up to enable the abstraction of the thermal shock conditions in different stages. The patterned nitriding, boriding and combination plasma process (PN + PNC) were evaluated in a series of industrial field tests to derive recommendations for suitable tool treatments.

Abstract: The features of the structure formation of diffusion layers obtained by technology, including preliminary surface treatment of steel products made of U8 steel and subsequent boriding in powder media, have been investigated. The pretreatment consisted of dynamic alloying in the superdeep penetration (SDP) mode with a SiC-based powder composition. As a result, the thickness of the diffusion layer increases, its porosity decreases, and the proportion of the high-boron FeB phase in the layer increases.

Abstract: This paper explores the thermochemical treatment of cemented carbides (CC), specifically the boriding process. Six different types of CCs with different size of tungsten carbide (TC) grains were chosen as experimental materials. They contained binders of different chemical compositions. In five CCs, the binders were pure metals: cobalt (four of them) and nickel (one of them). In the six one, the binder was a complex Ni-Co-Cr-based alloy. Samples of the different types of CCs were prepared by grinding and polishing and then half of them underwent boriding process. The experiment aimed to find how boriding affects the final properties of CCs and their structure. Microstructural changes in the materials were examined using X-ray diffraction and optical and electron microscopy. Changes in mechanical properties and wear resistance were evaluated using hardness testing and the Ball on Disk test. The experimental results, for example, shown that CC with nickel binder had lowest wear resistance from all tested sorts of CC.

Abstract: This paper evaluates the tribological behavior of borided AISI 316L steel after being exposed to a secondary process to form a thin film of a solid lubricant. The process known as Short Annealing Process (SAP), allows creating a thin film of boric acid (H₃BO₃) on the surface of metallic materials previously exposed to boriding. The H₃BO₃ film acts like solid lubricant due to its lamellar crystalline structure. First samples of AISI 316L were exposed to boriding to temperatures of 875, 925 and 975 °C during 2, 4 and 6 h each temperature. Then, samples were heated to 750 °C during 5 min and cooled to room temperature at 60 % of Relative Humidity. The tribological behavior of the treated samples was evaluated by pin-on-disk test equipped with friction coefficient measurement system. Samples were characterized by Scanning Electron Microscopy, X-Ray Diffraction and Vickers microhardness test. The results showed an evident influence of the experimental parameters on the thickness of the boride layers and their mechanical properties. The layer ́s thickness was ranged from 10.51±0.71 to 51.57±5.12 μm. The hardness of the coatings was increased from 264 to 1685 HV. Finally, the Coefficient of Friction was diminished from values of 0.7 for the as-received material to 0.29 for the borided samples and to 0.06 for those after SAP, which indicates that the post-treatment SAP enhances the tribological properties of the biomedical steel.

Abstract: Compositions of mixes for boriding of steelworks are offered. The entered components in composition of powdery blend are proved. Results of a microstructure and hardness of the strengthened surface after boriding deformed and cast steel are given. The possibility of boriding of a surface of founding in a casting mold is shown. The frequency rate of effective use of the saturating mix in operation is defined.

Abstract: The mechanical characteristics are determined to a FeB/Fe₂B coating applied in AISI L6 steel tool and blades make to cut paper. The thermochemical treatment was applied at temperatures of 1173, 1223 and 1273 K with permanence time of 0.5, 2 and 3 h for each temperature. The diffusion coefficient and activation energy for each phase is obtained for this boron coating on an AISI L6 steel. HRC test were made to establish the type of adherence (qualitative) and comparing with the VDI 3198 standard and the results were obtaining optimal classification of HF1-HF2 in condition for 3h of the three temperatures. The result by nanoidentation show hardness of 1000 - 2000 HV as well as the Young's modulus for each present phase of the coating. Through micrographs (SEM) are showing thicknesses up to 79.52 ± 18.82 μm for FeB and 97.80 ± 20.01μm for Fe₂B, a morphology sawn ́s type is evidence. Through EDS and x-ray diffraction are used to show the chemical elements formed.

Abstract: In this work, we will study the cyclic behavior (tension-compression under strain control) and the fatigue of 304L austenitic SS after application of a boriding thermochemical treatment. 304L specimens was borided in a solid medium at 900 °C for 4 hours. The phase analysis of boride layers formed at the surface was performed by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The obtained results show that the layers formed on 304L steel contained the following boride phases FeB, Fe₂B, CrB, Cr₂B, NiB and Ni₂B. The fatigue tests show that the boriding treatment improves the life a factor which may be greater than four. The borided specimens show a negative average stress during cycling which may explain the increase of fatigue life. Analysis of the fracture surface by SEM show that crack initiation takes place in the substrate rather than in the boron-treated area.

Abstract: The objective of this work is to predict for a given concentration, what will be the depth of the boride layer under set conditions using collision theory between atoms and diffusion by means of the Lattice Boltzmann Method.

Abstract: This paper studies the formation of iron boride on the surface in ductile iron 100-70-03 class exposed to a thermochemical treatment boron dehydrated paste. The formation of iron boride layers Fe₂B/FeB-type were obtained at temperatures of 1173 K, 1223 K and 1273 K, with exposure times of 8 hours of treatment. The study consisted in evaluating the growth kinetics of the boride layer on the surface of ductile iron boriding. Also the boride layers were determined by the XRD method, EDS. Also evaluated fracture toughness technique Vickers microindentation 15 and 30 microns from the surface with different loadings of iron boride microindentation formed on the surface.