Boriding Treatment Research Articles

Characterization and Wear Performance of Borided AISI 304 and UNS S31254 Stainless Steels

Abstract Austenitic stainless steels form the largest family of alloys in terms of number and applications. They are characterized by having good toughness, weldability, cold formability, and corrosion resistance in various situations. However, because they cannot harden by heat treatment, they exhibit low wear resistance. Suitable coatings can increase their wear resistance and expand their usability range. Boride coatings, with their high hardness and wear resistance are a good candidate for this purpose. In this work, samples of stainless steels, AISI 304 and UNS S31254, were subjected to liquid boriding at 950°C for 2 and 4 h. Optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Vickers hardness tests were performed, along with tests for micro-adhesive wear (fixed-ball type). The boriding treatment resulted in the formation of layers with high hardness, in the range of 1800 to 2000 HV, which is typical for boride layers. Micro-adhesive wear tests demonstrated the great increase in wear resistance obtained through this treatment.

Kinetics of Layers Produced on Niobium by Salt Bath Boriding

Abstract In this study, the growth kinetics of NbB2 (niobium boride) layers on pure niobium by boriding was described. The boronizing process was performed in a salt bath composed of borax (sodium borate) and aluminum (10 wt.%). The processing temperatures used were 1123, 1173, 1223, 1273, and 1323 K with residence times in the bath of 2, 4, and 6 h. The borided samples were characterized with respect to hardness and layer kinetics formation. Scanning electron microscopy (SEM), X-ray diffraction (XDR), and Vickers hardness tests were performed. The formation of niobium boride on the surface of pure niobium was confirmed by XRD analysis. The value of Vickers hardness of the layer was up to 2700 HV0.5. The growth kinetics were analyzed by measuring the depth of niobium boride layer as a function of time and temperature. The kinetics equation of the treatment has also been determined with Arrhenius equation K = K0 exp(−Q/RT). The results showed that the diffusion coefficient (K) of the process increased with treatment temperature. Activation energy (Q) for boriding treatment was calculated as 362 kJ/mol.

Micro-abrasive wear mechanisms of borided AISI 1020 steel

A boriding treatment was applied to AISI 1020 steel at 1000°C for 4h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and the Knoop microhardness test. The loads and abrasive slurry concentrations used in the micro-abrasion tests (fixed-ball) were 0.49–0.98N and 0.5–1.0g/cm³, respectively. Silicon carbide (SiC) abrasive powders (5µm) were used in the abrasion experiments. The wear coefficient and mechanisms were compared with those obtained from untreated samples. The XRD analysis revealed the presence of the Fe2B phase on the borided samples. The iron borided layer was 177µm thick and had a hardness of 2100 HK0.01. The wear mechanism for the borided samples was rolling abrasion while grooving abrasion with micro-rolling occurred in the untreated samples.

Microstructure and Mechanical Properties of Borided Inconel 625 Superalloy

The Ni- based superalloy Inconel 625 is extensively used owing to its high strength, excellent fabricability, good weldability and outstanding resistance to high temperature corrosion against aggressive environments. However, despite its unique properties and extensive use, its wear resistance is in some cases unsatisfactory. In this study, Inconel 625 was subjected to boriding treatments at different temperature and different durations. Microstructural characterization was made by conventional methods (scanning electron microscopy, optic microscopy, X-ray diffraction analysis) and mechanical characterization was made by microhardness and micro-abrasion wear test. Micro-abrasion wear tests were conducted against a AISI 52100 steel under 5, 7.5 and 10 N load in a 25 wt.% SiC slurry at room temperature. Microstructural results revealed that multi-phase boride layer (nickel boride, chrome boride and iron boride) and silicide layer were formed. The hardness and thickness of the boride layers were found to be 1175--2432 HV0.1 and, 6.61 -- 92.03 I¼m, respectively. Depending on the boriding temperature and time. In spite of silicide layer formation the wear resistance of borided Inconel 625 alloy increased up to 8 times thanks to the increase in the surface hardness which was caused by boriding process. The boriding treatment caused a transition in the wear mechanism. While grooving was observed in the untreated Inconel 625 samples, mixed (grooving and rolling) and rolling type wear was predominant in the borided samples.

An Evaluation of a Borided Layer Formed on Ti-6Al-4V Alloy by Means of SMAT and Low-Temperature Boriding.

In this paper, a nanocrystalline surface layer without impurities was fabricated on Ti-6Al-4V alloy by means of surface mechanical attrition treatment (SMAT). The grain size in the nanocrystalline layer is about 10 nm and grain morphology displays a random crystallographic orientation distribution. Subsequently, the low-temperature boriding behaviors (at 600 °C) of the SMAT sample, including the phase composition, microstructure, micro-hardness, and brittleness, were investigated in comparison with those of coarse-grained sample borided at 1100 °C. The results showed that the boriding kinetics could be significantly enhanced by SMAT, resulting in the formation of a nano-structured boride layers on Ti-6Al-4V alloy at lower temperature. Compared to the coarse-grained boriding sample, the SMAT boriding sample exhibits a similar hardness value, but improved surface toughness. The satisfactory surface toughness may be attributed to the boriding treatment that was carried out at lower temperature.

Boriding of Binary Ni–Ti Shape Memory Alloys

Abstract Boriding of binary Ni–Ti shape memory alloys was carried out in a solid medium at 1273 K for 2, 4, 6, and 8 h using the powder pack method with proprietary Ekabor–Ni powders. Characterization of the boride layer formed on the surface of alloys was done by optical microscopy and scanning electron microscopy. The presence of boride, silicide, and borosilicide phases in the boride layers was confirmed by X-ray diffraction analysis. The thickness and microhardness of the boride layers increased with increasing boriding time. Hardness profiles showed a rapid decrease in hardness moving from the boride layer to the main structure. The high hardness of the boride layer was attributed mainly to the formation of TiB2. A parabolic relationship was observed between layer thickness and boriding time, and the growth rate constant for the boriding treatment was calculated as 0.62×10−8 cm2 s−1.

Enhanced boronizing kinetics and high temperature wear resistance of H13 steel with boriding treatment assisted by air blast shot peening

Abstract A nanostructured surface layer was fabricated on H13 steel by means of air blast shot peening (ABSP). A much thicker borided layer on the ABSP sample can be synthesized by a duplex boronizing treatment (DBT) at 600 °C for 2 h, which is followed by at a higher temperature for a certain time. The borided layer was composed with monophase of Fe 2 B and the growth of it exhibited a (002) preferred orientation. Moreover, the activation energy of boron diffusion for the ABSP sample is 227.4 kJ/mol, which is lower than 260.4 kJ/mol for the coarse-grained counterpart. The results indicate that the boronizing kinetics can be effectively enhanced in the ABSP sample with DBT. The high temperature wear resistance of H13 steel with DBT can be improved significantly. Furthermore, the H13 steel with DBT assisted by ABSP possesses more superior wear resistance property at elevated temperatures than that of coarse-grained sample with DBT, which can be attributed to the fact that the thickness and microhardness of the borided layer can be increased with the help of ABSP. Meanwhile, the fatigue crack initiation and propagation in borided layer during the wear test can be impeded by the compressive residual stress and the refined grains in the borides of ABSP sample with DBT.

Microabrasion Wear Behavior of Fast-Borided Steel Tooth Drill Bits

ABSTRACTIn this study, the surface of steel tooth drill bits (Ni-Cr-Mo based) was subjected to the solid-state boriding treatment with 10- to 50-nm nanoboron powder. Boriding processes were carried out at a constant temperature of 1273 K for 30, 45, 60, 75, 90, and 105 min using a solid-state box boriding technique. Borided drill bit samples were characterized by conventional methods (microstructure, microhardness, X-ray diffraction, and chemical analysis). The wear behavior of borided samples was tested at different loads and sliding speeds by a microabrasion experimental setup. Metallographic studies showed that the boride layers have a sawtooth morphology and consist of FeB and Fe2B. The thickness and hardness of the boride layer were 35.29–202.56 μm and 1300–2333 HV0.1, respectively, depending on the duration. The wear resistance of borided samples increased significantly due to the increase in surface hardness and lubricating effect, both of which were caused by the boriding process. A groove wear mechanism prevailed in borided samples, whereas that of bare steel tooth drill bits (STDBs) was grooving, rolling, and mixed.

Fatigue and Cyclic Behavior of 304L Stainless Steel in the Presence of Boriding Surface Treatment

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.

Wear Behavior of a Borided Nickel-Based Self-Fluxing Thermal Spray Coating

Increasing the hardness of materials used in machines can lead to a longer useful life while decreasing maintenance downtime. However, high hardness usually results in an increase in brittleness of the material, which can be avoided by surface treatments, such as thermal spray coatings that are largely used to produce coatings with high resistance to wear and corrosion. This method has advantages, such as easy application, relatively inexpensive in comparison with other methods, and does not increase the brittleness of the base material. However, in some applications, the wear resistance may not be sufficient. To further improve the wear resistance of these coatings, a thermochemical boriding treatment can be subsequently applied to produce a duplex coating. In this work, an SAE 1020 steel was used as the substrate for the application of a thermal sprayed surface coating. The alloy applied is nickel based and self-fluxing with composition NiCrBSiC. The boriding treatment was subsequently performed at 850°C for 2 h. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Vickers micro-hardness and micro-abrasive wear tests were used to characterize the samples. The flame spray produced coatings of approximately 900 HV, which was increased to 1600 HV after the boriding treatment.

Characterization of Coatings Obtained by Boriding Niobizing Treatment of an AISI H13 Steel

Wear is responsible for numerous industrial problems leading to increased maintenance costs due to the necessity of replacing worn components or due to equipment failure and manufacturing process downtime. Surface treatments can improve performance because the component maintains its ductile interior but with significantly improved surface wear resistance while using a minimal amount of material. Niobizing the surface of tool steel leads to the formation of very hard coatings, in the range of 2300 HV, composed of niobium carbide but with limited thickness. Boriding also produces very hard coatings, on order of 2000 HV, but with a much thicker layer than attainable by the niobizing treatment. If both were applied to the same material they could potentially complement each other by forming a duplex coating with a thin, but very hard, surface coating supported by an inner layer with slightly lower hardness but substantially thicker. The objective of this work was to evaluate the wear resistance of a coating formed by the niobizing and boriding diffusion treatments. Boron and niobium coatings were prepared on AISI H13 tool steel by thermo-reactive diffusion treatment in molten borax with 10 wt% aluminum followed by the niobium carbide pack process. The boriding treatment was performed at 900°C for 2 h, followed by a pack process at 1000°C for 2, 4, and 6 h. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, micro-adhesive wear test, and Vickers micro-hardness were used to analyze the samples. The boriding and niobium carbide pack process produced coatings with thicknesses above 45 and 4 μm, respectively.

Characterization of Layers Produced by Boriding and Boriding-PVD on AISI D2 Tool Steel

Boride layers with high hardness and wear resistance were produced on AISI D2 tool steel by thermo-reactive treatment using borax with the addition of 10 wt. % aluminum. Subsequently, PVD treatments were performed on the borided layer. The samples were characterized using optical microscopy, scanning electron microscopy, X-ray diffraction, micro-hardness testing, and free-ball micro-abrasive wear test. The boriding treatment time was 4 h, followed by cooling in oil or air. The average thickness of the borided layers was 120 μm with a hardness ranging from 1400 to 1700 HV. The micro-abrasive wear tests were performed using an abrasive solution of silicon carbide. All layers produced exhibited a wear resistance much higher than that of the substrate. Samples with duplex PVD plus boriding treatments yielded the best wear performance, followed by the borided steel samples, and finally, the untreated quenched and tempered samples.

Production and Characterization of Boride Coatings on Flame-Sprayed Martensitic Stainless Steel

Thermal spray is a process with many industrial applications in surface protection against wear and corrosion. The benefits of these processes include increased component life and decreased equipment downtime. However, sometimes an even greater wear resistance is required for optimal results. In such cases, a secondary treatment may be performed to produce a duplex coating. The objective of this work is to evaluate the wear resistance of a borided flame-sprayed duplex coating using an AISI 410 martensitic stainless steel alloy and a flame-spray process. The boriding treatment was performed at 950°C with 2- and 4-h treatment time in liquid borax in which 10 wt. % of aluminum was added. Optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction, and Vickers micro-hardness were used to analyze the samples. Micro-adhesive wear tests were performed to evaluate the wear resistance of the coatings using the fixed-ball method. The duplex coating exhibited superior wear resistance and hardness. The flame-sprayed coating layer exhibited a base hardness of about 450 HV, which was increased four times to about 1950 HV by including the boriding treatment. The thickness of the borided layer was approximately 50 μm.

Influence of Boronizing Treatment on Fe–Mn–Al–Si–C Steel

Abstract Austenitic Fe–Mn–Al–Si–C steel provides excellent cold formability and lower density compared to conventional stainless steels. These steels owe their corrosion and oxidation resistance to their aluminum and silicon contents, and the stability of their gamma phase is due to manganese and carbon alloying elements. The production of a boride layer with high hardness can significantly increase its surface hardness and consequently its wear resistance. In this work, Fe–31Mn–7.5Al–1.3Si–0.9C steel samples were subjected to a boriding treatment for 4 h at 900°C. The composition of the bath was 90 % borax and 10 % aluminum. Boride layers with high hardness levels were obtained (1900 HV). There was also a marked increase in wear resistance of the material.

Application of Artificial Neural Network for Prediction of Boride Layer Depth Obtained on XC38 Steel in Molten Salts

This paper discusses an application of neural network system on the performance of boride layer thickness. Boriding treatment was carried out in three different molten salts consisting of borax (Na2B4O7) added to boron carbide (B4C), aluminum (Al) and silicon carbides (SiC). The substrate used in this study was XC38 steel. Borides layers involved in this work was obtained from a boriding treatment at the temperature range of 800-1050 °C with 50°C interval for 2, 4 and 6 h. A numerical experiment using normalized and binarized values was carried out, using a back-propagation algorithm in ANN. The modeling shows that for the three bath the depth of boride layer was predicted with good accuracy, with a highest performance of normalized values along experimental data range.

Low-temperature boriding of high-carbon steel

Boriding has attracted great interests in improving mechanical performance of materials. The high processing temperature and the relatively thin boride layer, however, have limited its applications. Here we report a method to boronize high-carbon steels at a relatively low temperature (780°C). Using the arc melting process, a thick (>400μm) boronized coating is obtained. Two iron-boride phases (FeB and Fe2B) coexist in the borided layer. The surface hardness of the steel is increased by ~57%, while the friction is reduced by ~17% and ~65% under steel-steel and steel-diamond contacts, respectively. In a 40,000cycle wear test, the wear track on the steel surface becomes invisible after the boriding treatment. The low-temperature process developed in this study is applicable to other materials and is effective in making thick boride coatings with less energy consumption.

Diffusion kinetics of boron in the X200CrMoV12 high-alloy steel

In this work, the kinetics of formation of the boride layers (FeB/Fe2B), formed on the X200CrMoV12 steel used for the coldworking, was investigated. The boriding treatment was carried out in the powder mixture consisting of 5%B4C, 5% NaBF4 and 90% SiC. The boriding parameters are : 900, 950 and 1000?C with treatment times of 2, 4 and 6 h. The obtained borided layers (FeB/Fe2B) were characterized by the following experimental techniques: optical microscopy, scanning electron microscopy coupled to EDS analysis and XRD analysis. The kinetics of boron diffusion in the X200CrMoV12 steel was also studied. As a result, the time dependence of the borided layers thicknesses followed a growth parabolic law. The boron activation energy was estimated as 199.37 kJ mol-1 for the X200CrMoV12 steel. A full factorial design with 2 factors at 3 levels was employed to estimate the total boride layer thickness as a function of the boriding parameters (time and temperature) and a simple equation was proposed. Finally, an iso-thickness diagram was given as a tool to predict the total boride layers thicknesses in relation with the practical utilization of this kind of steel.

Boriding of high carbon high chromium cold work tool steel

High-carbon high-chromium cold work tool steels are widely used for blanking and cold forming of punches and dies. It is always advantageous to obtain an increased wear resistant surface to improve life and performance of these steels. In this connection boriding of a high-carbon high-chromium cold work die steel, D3, was conducted in a mixture of 30% B4C, 70% borax at 950 °C for two, four and six hours. Case depth of the borided layer obtained was between 40 to 80 μm. After boriding, the surface hardness achieved was between 1430 to 1544 HV depending upon the process time. X-ray diffraction studies confirmed the formation of a duplex compound layer consisting of FeB and Fe2B. It is generally considered that FeB is undesirable because of its inherent brittleness. Post boriding treatment (homogenization) transformed the compound layer into single-phase layer of Fe2B, while surface hardness decreased to 1345-1430 HV. Pin-on-disc wer test showed that wear resistance of the borided samples was superior as compared to non-borided material and increased with boriding time.

Friction and Wear Mechanism at Elevated Temperature of H13 Steel with a Duplex Pack Boriding Treatment

The friction and wear performance of H13 steel after a duplex pack boriding treatment assisted by high-energy shot peening the un-borided one were investigated. The experimental results show that a layer of monophase of Fe2B formed on H13 steel after the two-step pack boriding treatment assisted by high-energy shot peening; the high-energy shot peening can remarkably enhance the boriding process. The wear rate at elevated temperature of the boronized H13 steel may be reduced up to 30% in comparison with that of the bare steel. The oxide scales formed on the wear surface of the boronized steel and the bare steel all are Fe2O3. A wear mechanism concerning the elevated temperature wear is proposed that the boronized H13 steel may firstly suffered from fatigue flake of boride layer and subsequently oxidation wear due to its high hardness and excellent oxidation resistance. However, the elevated temperature wear mechanisms of the bare steel are synergistically oxidation wear and abrasive wear.

Corrosion behavior of borided AISI 304 austenitic stainless steel

Purpose – The paper aims to clarify the effect of boriding on the corrosion behavior and mechanical properties of AISI 304 austenitic stainless steel. Design/methodology/approach – The commercially available steel was subjected to a boriding treatment with Ekabor III powders at temperatures of 1,223-1,273 K with boriding durations of 2-4 h. Microstructural characterization of the steel was carried out with optical microscopy, scanning electron microscopy and X-ray diffraction analyses. Static immersion corrosion tests were made using a 10 percent H2SO4 acid solution and salt spray tests were carried out in accord with the ASTM B-117 standard. Findings – Grain boundary precipitation of carbides was observed in the transition zone beneath the boride layers. The corrosion resistance of the steel against the acid solution increased to about seven times its untreated value with the boriding treatment. Research limitations/implications – The boride coating improved the corrosion resistance of the AISI 304 stainless steel against acidic media, but suffered from spalling in the salt spray test. Future work will focus on improving the adhesion between the coating and the substrate by changing the parameters for the boriding process. Practical implications – Pack boriding is a simple, environmentally friendly coating process and can be recommended for use in small and medium enterprises. The boride coatings deposited have potential in further improving the wear and corrosion resistance of stainless steels. Originality/value – The outcome of the research is of great importance for the industry using wear- and corrosion-resistant coatings.