Boride Coatings Research Articles

Increasing corrosion resistance of AISI 1010 steel by boride coatings

AbstractBoriding is the process of coating the metal surface with a ceramic metal boride layer by the diffusion method. Iron borides, one of the metal borides, are called ceramics because they are covalently bonded compounds. Iron boride coatings contain strong Fe–B and B–B covalent bonds. In this study, the effect of boronizing on the corrosion resistance of AISI 1010 steel was investigated. Baybora‐1 which has recently been patented was used as boronizing agent. AISI 1010 steel was borided at 950°C for 2, 4, and 6 h using the solid method. The microstructure, hardness, and corrosion rate of the samples were investigated. The change in the corrosion rate of the samples was determined by the corrosion test specified in the ASTM G31‐72 standard. The results showed that the hardness of the iron boride layer formed on the surface as a result of the boronizing process was greater than that of the matrix. As a result of the boriding process, the hardness of the iron boride layer on the steel surface reached approximately eight times the hardness of the substrate matrix. The thickness of the iron boride layer on the steel sample surface was measured at 950°C for 2 and 6 h, respectively, as 45 ± 12 and 155 ± 13 µm. It was concluded that the boriding process increased the corrosion resistance of steel.

RAY PHASE AND MICROSTRUCTURAL ANALYSIS OFHARDENING COATINGS OBTAINED BYSELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS IN COMBINATION WITH HEATING OFA MIXTURE OF 𝑨𝒍+𝑩𝟐𝑶𝟑BASED ON HIGH-FREQUENCY CURRENT TREATMENT

The paper describes the results of studies of hardening boride coatings obtained during the implementation of the process of self-propagating high-temperature synthesis. These coatings were composite materials based on aluminum oxide and boron. The obtained coatings were subjected to X-ray phase and microstructural analysis, which showed the maincomponents of the resulting compositions and made it possible to assess the thickness and structure of the coating-base metal transition area. The different content of silicon and iron makes it possible to assess the occurrence of surface chemical and metallurgical processes during self-propagating high-temperature synthesis when heating of the base mixture samples on high-frequency current treatment. The expediency of using high-frequency current treatment in combination with the process of self-propagating high-temperature synthesis for better-quality spattering of the hardening coating is shown. The appearance of two areas in the coating with different thickness and structure of the coating is established.

Bilayer growth kinetics and tribological characterization of boronized AISI M2 steel

Abstract The AISI M2 steel has been treated by solid boriding between 1123 and 1273 K for an exposure time of 2–8 h. In these circumstances, a bilayer constituted by FeB and Fe2B has been formed with interfaces nearly flat. The tribological behavior and decohesion resistance of boride coatings were studied by using the following characterizations: (Rockwell-C cohesion, pin-on-disc and wear scratch tests). The modeling of process kinetics was undertaken based on two different approaches (the mass balance equations and the integral method). The assessed values of boron activation energies in FeB and Fe2B arising from the two models were nearly similar. In addition, the predicted layers’ thicknesses at 1243 and 1273 K during 10 h were concordant with the experimental values.

Adhesive wear behavior of gas tungsten arc welded FeB-FeMo-C coatings

Abstract In this article, a gas tungsten arc welding is used as a high energy density beam to form a surface over 0.15% carbon steel with FeB, FeMo, and graphite powders. The microstructure, microhardness, and dry-sliding wear behavior of the composite coating were investigated using optical micrography, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectrometry. Microstructural investigations reveal that FeB-reinforced coating exhibited a homogeneous microstructure that consists of dendrites and eutectic. A lot of types of carbide and borides were formed. MoB4, Fe2MoC, B8C, Mo2BC, MoB, Fe3Mo, Fe3B, B25C, Fe7C3, FeB, Mo2B5, and MoC were seen in coated surfaces. Graphite iron boride coatings obtained by the gas tungsten arc welding process improved the wear resistance of carbon steel.

Synthesis and oxidation behavior of Ti0.35Al0.65By (y = 1.7–2.4) coatings

The effect of B concentration on phase formation and oxidation resistance of (Ti0.35Al0.65)By coatings with y = 1.7, 2.0, 2.4 was investigated. Elemental B targets in radio frequency mode and a compound Ti0.4Al0.6 target in direct current mode were sputtered. The B concentration was varied systematically by adjusting the applied power to the respective magnetrons, while keeping the power supplied to the magnetron with the Ti0.4Al0.6 target constant. Measured lattice parameters and elastic properties are consistent with ab initio predictions. The oxidation resistance at 700 °C in air for up to 8 h was compared to a cathodic arc evaporated (Ti0.37Al0.63)0.49N0.51 coating with an Al/Ti ratio of 1.69 ± 0.20 which is very similar to 1.84 ± 0.40 for the boride coatings. Scanning transmission electron microscopy imaging revealed oxide scale thicknesses of 39 ± 7 and 101 ± 25 nm for (Ti0.35Al0.65)B2.0 and (Ti0.37Al0.63)0.49N0.51 after 8 h, respectively. Hence, the close to stoichiometric diboride outperforms the nitride coating. This behavior can be understood based on composition and structure analysis of the oxide scales: While the protective layer on the diboride is primarily composed of Al and O, the porous oxide layer on the nitride coating contains Ti, Al and O.

Boride Coatings on Steel Protecting it Against Corrosion by a Liquid Lead-Free Solder Alloy

The goal of this research is to study the applicability of the diffusion boriding process as a high-temperature thermochemical heat treatment to enhance the lifetime of steel selective soldering tools. The main purpose of the work is to discuss the behavior of double-phase (FeB/Fe2B) iron-boride coating on the surface of different steels (DC04, C45, CK60, and C105U) against the stationary SAC309 lead-free solder liquid alloy. The boride coating was formed on the surface of the steel samples through the powder pack boriding technique. The microstructure of the formed layer was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The borided samples were first cut in half and then immersed into a stationary SAC309 lead-free solder liquid alloy (Sn–3Ag–0.9Cu) for 40 days. Microstructure examinations were performed by SEM with energy-dispersive spectroscopy and an elemental distribution map after the dissolution test. Excessive dissolution/corrosion of the original steel surface was observed at the steel/SAC interfaces, leading also to the formation of Fe–Sn intermetallic phases. This was found to be the major reason for the failure of selective soldering tools made of steel. On the contrary, no dissolution and no intermetallic compounds were observed at the FeB/SAC and at the Fe2B/SAC interfaces; as a result, the thicknesses of the FeB and Fe2B phases remained the same during the 40-day dissolution tests. Thus, it was concluded that both FeB and Fe2B phases show excellent resistance against the aggressive liquid solder alloy. The results of the dissolution tests show a good agreement with the thermodynamic calculations.

Temporal Evolution of Pressure Generated by a Nanosecond Laser Pulse Used for Assessment of Adhesive Strength of the Tungsten–Zirconium–Borides Coatings

The article presents theoretical and experimental study of shock waves induced by a nanosecond laser pulse. Generation of surface plasma pressure by ablation of the graphite absorption layer in water medium and shock wave formation were analyzed theoretically and experimentally. The amplitude and temporal variation of the shock wave pressure was determined basing on a proposed hydrodynamic model of nanosecond laser ablation and experimentally verified with use of a polyvinylidene fluoride (PVDF) piezoelectric-film sensor. The determined pressure wave was used for examination of adhesive strength of tungsten–zirconium–boride coatings on steel substrate. The magnetron sputtered (MS) W–Zr–B coatings show good adhesion to the steel substrate. The obtained experimental results prove the correctness of the proposed model as well as the suitability of the procedure for assessment of adhesive strength.

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.

ИССЛЕДОВАНИЕ МИКРОТВЕРДОСТИ БОРИДНЫХ ПОКРЫТИЙ, ПОЛУЧЕННЫХ НА СТАЛИ 65Г ИЗ РАЗЛИЧНЫХ СОСТАВОВ БОРИРУЮЩИХ СМЕСЕЙ

The surface of the working organs of tillage equipment is subject to wear during operation. To obtain a surface layer of a part with high hardness and strength, corrosion resistance and abrasive resistance, there are used methods of chemical-thermal treatment, which consist in simultaneously exposing the surface to temperature and substances that can react chemically with the organ material. In this article, we consider the method of diffusion boronizing in coatings using the method of non-contact heating by high-frequency currents to study the microhardness of various boride coatings. (Research purpose) The research purpose is in studying the mechanical properties of boride coatings obtained by boronizing by heating 65G steel with high-frequency currents using various borating mixtures. (Materials and methods) An HDTV-40AV furnace was used to study the processes of boronizing using high-frequency surface heating. The temperature of the boronizing process was 950-1250 degrees Celsius, and the saturation process time was 40-180 seconds. Boron-carbide-based compositions were used. (Results and discussion) As a result of the studies, the microhardness of samples with different compositions of boronizing mixtures was studied. 65G steel was boronized. (Conclusions) According to the results of the study, the greatest microhardness was obtained using composition 6, containing manganese boride crystals (HV100 of 27570 megapascals, coating thickness of 250 micrometers) for a time of 120 seconds. However, the most suitable and less expensive to use in the agricultural industry were compositions based on boron carbide.

Boron Diffusion During Carbon Steel Boriding

Protective boride coatings are obtained by chemical-thermal treatment of powder mixtures during induction furnace heating and micro-arc chemical-thermal treatment. Their usage can significantly increase the reliability and durability of steel products. The calculated composition of the saturating charge and the welding flux used to boride steel 20 samples demonstrates that obtained boride diffusion coatings are characterized by high hardness and an extensive diffusion zone. The most optimal composition of the charge that contains iron and boric acid is found to be in the proportion of Fe-25%+H3BO3-75 %.
 The analysis of the distribution of microhardness over the cross section of coated samples is carried out. The comparative data for the diffusion coefficients and the thickness of the diffusion layers obtained experimentally are presented.
 The application of the discussed methods makes it possible to intensify the process of diffusion boriding and to ensure the formation of an extensive diffusion zone on the surface of carbon steel products with a high rate of hardening zone formation. The duration of the process is 5 minutes for the induction treatment and 54.05 s for micro-arc chemical-thermal surfacing. It is the main advantage of the experimental techniques mentioned above.

Life of Boride Coatings on Steels Under Cyclic Contact Load

Life of Boride Coatings on Steels Under Cyclic Contact Load

Influence of the Composition of Boriding Mixture on the Saturation of the Surface of Various Steels with Boron during High-Speed HFC-Boriding

The use of borate fluxes is an important component of the part hardening process by HFC-heating. The article discusses the possibility of using various coatings to saturate the surface of steel parts, as well as the features of using various boriding agents. Microstructures of the obtained boride coatings at various fractions of the boriding agent have been considered, and the areas of carbide inclusions and average thickness of the resulting coatings have been analyzed. The expediency of P-0.66 fused flux using and changes in the resulting coatings due to the changes in the mass fraction of this flux in various boriding mixtures have been investigated. Based on the obtained data on the microstructures of boride coatings, conclusions were made concerning the most appropriate compositions of boriding mixtures and the mass fraction of fused flux in their composition.

Analysis of Wear Resistance of Borided Steel C45.

The wear resistance of diffusion coatings in conditions of specific pressures of 3, 7 and 10 MPa was studied. The boride coatings were prepared by means of diffusion methods using C45 steel as the substrate material. Research on the microstructure and redistribution of chemical elements on wear surface of a borided layer was carried out. It was found that the boride coatings should be used under a specific pressure of 7 MPa. It was found that the wear of friction couple coating of steel C45 under specific pressure of 3 MPa proceeds according to the oxidation wear mechanism, while under specific pressures of 7 and 10 MPa the abrasive wear prevails. The wear-induced segregation of atoms in coatings was studied using secondary mass-spectroscopy method (SIMS). Increased C, O, and B concentrations were noticed at the wear surface on depth from 50 to 2000 Å. The secondary wear-induced structure formation on the wear surface resulted in high wear resistance of diffusion borided coatings.

Oxidation of boron-titanium thin film coating during cyclic tests on thermal shock

The results of experiments on cyclic thermal shock tests of promising neutronabsorbing titanium boride coatings are presented. It has been established that the main effect is the high-temperature oxidation of titanium boride with the formation of titanium and boron oxides. The regularities of changes in the oxidation parameters during cyclic thermal shock tests are determined.

Features of the formation of a diffusion layer and the mechanism of diffusion during boronizing of steels

The paper presents the results of studies on the formation of a diffusion layer during the boriding of steel with a carbon content of 0.38 wt%. The study of diffusion coatings by SEM and TEM methods allows one to more clearly determine the mechanisms of diffusion of boron atoms and the formation of diffusion boride coatings. Diffusion of boron in the processes of diffusion boriding of iron-carbon alloys proceeds by a mixed mechanism: the delivery of active boron atoms to the diffusion front proceeds along the grain and phase boundaries. The reaction mechanism is realized by a gradual substitution of carbon with boron in iron carbides. Due to the continuous diffusion of boron, the reaction boundary is constantly moving in the direction from the surface to the core of the saturated material. In this case, as the diffusion proceeds, the concentration of carbon atoms under the boride layer constantly increases. This provides resistance to diffusion of boron atoms by the atomic mechanism and provokes diffusion by the reaction mechanism.

Advanced iron boride coatings to enhance corrosion resistance of steels in geothermal power generation

ABSTRACT Iron boride coatings obtained by the CVD-based thermal diffusion process are proposed and evaluated for the first time for high-temperature corrosion and scaling conditions in geothermal power generation. The testing results in different corrosion environments are presented. The influence of structure and surface composition on the materials’ performance is demonstrated. The dual-layer boride-based coatings successfully withstand the actions of high temperature/high pressure water and steam with a presence of H2S, CO + CO2, chlorides and hydrocarbons in simulating conditions and strong acidic environments. They demonstrated minimal scaling and corrosion when the materials were immersed into the modelling mixes of chloride salt solutions with SiO2 or SiO2+Fe2O3 at elevated temperatures and into the brine solution at boiling. These advanced ceramic coatings and technology should promote significant extension of the steels’ service life in harsh geothermal-related corrosion environments.

Strengthening Protective Boride Coatings with SHS-Produced Fe2Al5

Strengthening Protective Boride Coatings with SHS-Produced Fe2Al5

The Effect of Atmosphere Composition on the Mechanism of Destruction of a Boride Coating on the Surface of a Die Steel during Thermal Cycling

The state of the surface and structure of the diffusion boride coating on the substrate of die steel have been studied after thermal cycling under a constant load of 193 N in hydrogen, nitrogen, and air atmospheres. It is shown that the degradation of boride coating in air occurs due to the development of oxidative processes beneath the coating at the boundary with the steel substrate. In air and nitrogen atmospheres, thermal cycling causes cracking of the boride coating with the formation of quasi-periodic cracks that damage only the boride layer and do not penetrate the steel. Thermal cycling in reducing and inert atmospheres leads to an increase in the values of the microhardness and elastic modulus of the coating due to the diffusion of nitrogen and hydrogen into (Fe,Cr)2B borides.

Influence of Iron Boride Coating on Flow‐Accelerated Corrosion of Carbon Steel

Flow‐accelerated corrosion (FAC) often occurs in piping systems made of carbon steels and other steels and alloys in power generation and mineral processing, when the products are subjected by extremely high‐velocity corrosive fluid flows. Under these extreme conditions, dissolution and subsequent degradation and thinning of the metallic surfaces occur due to corrosion–erosion resulting in a quick rupture of the piping products. Herein, iron boride‐based coatings obtained through the proprietary thermal diffusion process are selectively applied onto the inner surface of carbon steel A106B piping sections to protect the steel against FAC. The coated and uncoated steel piping sections are tested using the high‐turbulence corrosion loop device with flow rates up to 120 gal min−1 (≈450 L min−1) in boric acid‐based solutions. Changes of wall thickness of the piping sections and their structures are examined and evaluated. The pipe sections with iron boride coatings demonstrate significantly lower degradation in the studied FAC conditions compared with the bare carbon steel. Promising behavior of the coating can be explained by its well‐consolidated double‐layer structure composed of iron borides with high hardness, chemical inertness, and strong diffusion‐induced bonding between the protective layers and the steel substrate.

Mechanical and tribological behaviour of titanium boride coatings processed by thermochemicals treatments

ABSTRACT The present work aims to study the mechanical and tribological properties of titanium boride layer processed by a thermochemical boriding treatment, which was carried out in a salt bath consisting of 70% borax and 30% silicon carbide. The boriding temperatures were 850°C, 950°C and 1000°C with holding times of 2, 4, 6 and 8 h. The analysis by optical and scanning electron microscopy and X-ray diffraction method confirmed the formation of a single-phase layer of titanium diboride (TiB2) in the substrate surface. The thickness of the boride layer increases with time and temperature, reaching a maximum value of 50 μm. The microhardness was evaluated for the substrate and the boride layer. Additionally, nanomechanical characterization of the layer was carried out by nanoindentation tests. The influence of this treatment on the coefficient of friction and on the wear rate in a simulated medium of the body fluid was also studied.