Abstract: A simple diffusion model is proposed to estimate the growth kinetics of Fe2B layers created at the surface of pure iron. This model employs the mass balance equation at the Fe2B/substrate interface to evaluate the boron diffusion coefficient (DFe2B) in the boride layer. The Fe2B layers were formed using the paste boriding process, at four temperatures with different exposure times. Analysing the results, the evolution of the parabolic growth constant (k) of the Fe2B layer is presented as a function of boron concentration and boride incubation time [t0(T)]. Furthermore, the instantaneous velocity of the Fe2B/substrate interface and the weight gain of borided pure iron were estimated for different boriding temperatures. Finally, to validate the diffusion model, the boride layer thicknesses were predicted and experimentally verified for two boriding temperatures and for different treatment times.

Abstract: Two-step process: carburizing followed by boriding was applied to the formation of borocarburized layers. The boride layer formed on the substrate of changeable chemical and phase composition (e.g. borocarburized layer) was called “gradient boride layer”, in contrast to “typical boride layer”, formed on the substrate of constant chemical and phase composition. Two borocarburized layers, of different carbon concentration–depth profiles in carburized zone, were investigated. Higher abrasive wear resistance, but lower low-cycle fatigue strength characterized both layers in comparison with the carburized layer. The influence of carbon concentration–depth profile beneath iron borides on low-cycle fatigue strength was analyzed. The results showed that carburized zone beneath iron borides had to meet the same requirements, which are characteristic of carburized layers of high fatigue resistance. The “ideal” carbon concentration–depth profile beneath iron borides should be characterized by: relatively low carbon concentration beneath iron borides, providing a limited amount of retained austenite; adequately low core carbon content; and relatively high case depth. As a result, the fatigue performance of borocarburized layer can approach a limit obtained for carburized layer.

Abstract: The invention discloses a new method for surface boriding of hard alloy, which sequentially comprises the following steps of: removing an oxidation layer on the surface of the hard alloy; embedding the hard alloy into a solid boriding agent, putting the mixture into a nearly-closed boriding container, and putting the container into an induction heating furnace; vacuumizing the furnace, stopping vacuumizing until the vacuity is over 100 Pa, and filling inert gas or hydrogen; after the gas in the furnace reach the pressure, starting to perform induction heating to reach the boriding temperature of between 800 and 1,300 DEG C, and performing heat preservation for 0.5 to 8 hours to realize gas-solid phase boriding. The solid boriding agent comprises the following components in percentage by weight: 5 to 50 percent of boron supply agent, 2 to 40 percent of activating agent and the balance of fillers, wherein the boron supply agent is one or more of powdered B4C, BN and amorphous boron; the activating agent is two or more of powdered KBF4, NaBF4, NH4BF4, (NH4)2CO3, rare earth oxide and Mg powder, and one of the mixture is an activating agent containing a B element; and the filler consists of graphite powder granules and SiC powder or Al2O3 powder. Through the method, the boriding thickness of sintered hard alloy blank is more than 0.1 millimeter and is close to 1 millimeter, so the surface abrasion resistance of the hard alloy is improved greatly.

Abstract: This study evaluated the indentation size effect on the Fe 2 B/substrate interface using the Berkovich nanoindentation technique. First, the Fe 2 B layers were obtained at the surface of AISI 1018 borided steels by the powder-pack boriding method. The treatment was conducted at temperatures of 1193, 1243 and 1273 K for 4, 6 and 8 h at each temperature. The boriding of AISI 1018 steel resulted in the formation of saw-toothed Fe 2 B surface layers. The formation of a jagged boride coating interface can be attributed to the enhanced growth at the tips of the coating fingers, due to locally high stress fields and lattice distortions. Thus, the mechanical properties achieved at the tips of the boride layer are of great importance in the behavior of borided steel. Applied loads in the range of 10 to 500 mN were employed to characterize the hardness in the tips of the Fe 2 B/substrate interface for the different conditions of the boriding process. The results showed that the measured hardness depended critically on the applied load, which indicated the influence of the indentation size effect (ISE). The load-dependence of the hardness was analyzed with the classical power-law approach and the elastic recovery model. The true hardness in the tips of the Fe 2 B/substrate interface was obtained and compared with the boriding parameters. Finally, the nanoindentation technique was used to estimate the state of residual stresses in this critical zone of the Fe 2 B/substrate interface.

Abstract: The boronising behaviour of pure iron and Fe–Mn alloys (1, 2, 4, 8, 12 and 16 wt-%Mn) was investigated by ‘pack boronising’ at 1100°C for 3 h to determine the effect of Mn. FeB and Fe2B polyphase exist on all the boronised Fe–Mn alloys, and Fe–16 wt-%Mn alloy also has MnB2 phase in the boride layer. The usual crack on the interface of FeB and Fe2B was not observed for the boronised Fe–Mn alloys with 12 wt-% or more Mn. The same sawtooth-like morphology of the boride layer occurs on the pure iron and the Fe–Mn synthetic alloys without a clear transition zone. The distribution of Mn in the matrix and the boride layer is almost even. The average boride layer thickness is 280 μm and is independent of Mn content. The microhardness values are between 1700 and 2150 HV without a clear dependence on the amount of Mn.

Abstract: Repeated fast surface temperature transients can damage the materials and/or their surface treatments by thermal fatigue. This happens in aluminium diecasting devices. One conducted thermal fatigue tests with samples of hot work tool steel, respectively untreated, simply borided and protected by a multi-layer. In the last case, top coat is yttria stabilised zirconia (YSZ), followed by a nickel superalloy and then a borided layer (undercoat). The zirconia coating was applied with plasma spray. The multi-layer showed poor resistance during the thermal fatigue tests. Better understanding these tests and the resulting thermal fatigue observed on the treated materials was achieved by a lifetime model based on Coffin–Manson equations.

Abstract: The invention relates to an economical boriding_nitrocarburizing agent which is characterized in that: the economical boriding_nitrocarburizing agent is composed of 33 parts of borax, 7 parts of carbamide, 10 parts of charcoal (more than or equal to 100 meshes), 6 parts of silicon iron (more than or equal to 100 meshes), 4 parts of rare earth ferrosilicon alloy (more than or equal to 100 meshes),4 parts of sodium fluosilicate, ammonium bicarbonate and 22 parts of ocher (more than or equal to 100 meshes) by weight parts The rare earth ferrosilicon alloy and the ammonium bicarbonate are addedin the boriding_nitrocarburizing agent for catalyzed boriding carbonitriding, so as to effectively improve the penetrating rate and lead the depth of the boriding layer to reach 120-700mm, and the boriding layer is a FeB homogeneous structure which has high hardness and has good combination with a basal body structure; a nitrocarburizing transit layer close to the boriding layer is formed owning to the nitrocarburizing, the harness of the transit layer is not only increased, but also the thickness of the whole boriding_nitrocarburizing layer is increased, the hardness gradient is obviously reduced and the spalling of the boriding layer can be avoided The boriding_nitrocarburizing agent has wide source, low price and high cost performance and is economical and practical

Abstract: This study focuses on tribological performance of as-received and borided Ti6Al4V alloys against ceramic counterfaces (Al2O3 and Si3N4 balls) in water. The wear mode of the alloy changed from ploughing to polishing by achieving a remarkable reduction in wear loss upon boriding. On the borided surface, the destructive action of the Si3N4 ball was very limited, when compared to that of the Al2O3 ball.

Abstract: The invention discloses a heating processing technology of a metal steel tube, and belongs to the field of heat processing methods. The heating processing technology of a metal steel tube is characterized by adopting a method combing ferrite chemical treatment and austenite heat treatment; firstly carrying out low-temperature chemical heat treatment of sulfonitriding; then carrying out high-temperature chemical heat treatment of sulfonitriding over the critical temperature; simultaneously carrying out high-temperature chemical heat treatment of boriding over the critical temperature; then implementing austenite nitriding; and finally hardening and tempering. The manufactured steel tube has good quality and long service life, and the construction cost is low, and the whole process is environment-friendly.

Abstract: Surface treatments of engineering materials are important for serviceable engineering components. One of the thermo-chemical surface treatments of steel based materials is the boriding process. In this study, low alloy steel substrates were borided by pack boriding process at 900 °C. Experimental indentation tests were conducted on Dynamic Ultra-micro Hardness test machine, under applied peak loads of 800 mN, 1000 mN, 1200 mN and 1400 mN. To get the mechanical properties of FeB layers, the resulting load–unload test data of the samples obtained from the experimental indentation tests were analyzed and curve-fitted in Kick’s and Meyer’s law for the loading and the unloading part of the load-unload curve respectively. Then, a set of analytical functions that take the pile-up and sink-in effects into account during instrumented sharp indentation were solved using numerical methods. These analytical functions were defined within an identified representative plastic strain, er, for the Vickers indenter geometry as a strain level that allows for the description of the indentation loading response independent of strain hardening exponent, n. The mechanical characterization of samples, finite element modeling was applied to simulate the mechanical response of FeB layer on low alloy steel substrate by using ABAQUS software package program.

Abstract: The invention discloses a solid boriding process of a cold-drawing inner die of a seamless steel pipe, which is used for solving the problems that the traditional surface carburization and chromeplating process of inner die metal has the disadvantages of serious pollution to the environment, short service life, high cost and the like because of the emission of waste liquid The process comprises the steps of preparation and treatment, packaging, boriding treatment, heat treatment after boriding and cleaning and polishing

Abstract: FIELD: metallurgy. ^ SUBSTANCE: powder-like composition for boriding steel items contains following components, wt %: boron carbide 45-65, sodium fluoride 5-8, high-aluminous corrosion resistant cement on base of calcium aluminates HACRC-75-0.5 30-35, wood coal carburizer 8-12. ^ EFFECT: strengthened layer on steel items at repeated usage of saturating mixture. ^ 2 tbl

Abstract: The invention discloses a lightweight rapid granular boriding medium, which adopts ferroboron (Fe-B) as a source of boron, potassium fluoborate (KBF4) and ammonia bicarbonate (NH4HCO3) as energizers, and industrial pure aluminum oxide (Al2O3) as a filler. The boriding medium has the characteristics of high boriding speed, the borided layer structure of substantially single-phase Fe2B or (Fe/M)2B, the hardness of the borided layer of HV1,600 to 2,100, clean borided part surface, no need of washing and boriding medium sterilization, reusability and the like. The boriding medium can reach an advanced level both at home and abroad. For example, a borided knife clip of a splitting machine has the service life which is seven times that of a nitrided knife clip and twice that of a knife clip sprayed with a hard alloy; a baking-free brick mould, a sand brick mould and a refractory brick mould are borided to achieve the service life which is over fourth times that of a carburized mould; fittings, such as oil well pump pipes, couplings, centering devices and the like, of petroleum machinery use the boriding medium so as to achieve resistance to wear and corrosion and greatly prolonged service life; and after being borided, Q235 steel base plates required to be disassembled and replaced after 15 days under the abrasion of a grinding material can be used for more than half a year so as to achieve remarkable economic benefits.

Abstract: Boride layer was formed on the surface of Cr12MoV after being treated by boronizing technology, and it has high hardness, excellent high temperature oxidation resistance and other characteristics so the boronizing process are widely used in the heat treatment technology of mold and wear-resistant workpiece. But the boronizing technology also has disadvantages such as larger brittleness in the boronizing layer. In order to improve Cr12MoV boriding organizations, it is found that the infiltration of rare earth elements can improve the performance of a single boride layer. In this paper, by changing the temperature, time, rare earth addition and other parameters , the optimization parameter was obtained. and this could make infiltration layer more compact. The results of experiment also showed that the hardness and wear resistance of boride layer are significantly improved.

Abstract: Solid powder boriding experiment was carried out on TC4 titanium alloy surface with method of RE(rare earth)-boriding at the temperature of over 1000°C. By means of XRD, SEM and EDS, phase composition, microstructure and morphology of TC4 titanium alloy after RE-boriding were investigated. The effect of rare earth on phase composition was discussed. Results of the experiment showed that the diffusion layer was composed of top-layer TiB2 and sub-layer TiB whiskers with the highest thickness being 25μm. The XRD results revealed TiB-TiB2 biphasic B-Ti compounds layer formed on the surface of TC4 after RE-boriding. The high content of B and Ce in the surface layer showed rare earth increased the absorption and concentration of B atoms.

Abstract: Wear tests were developed in two different equipments, designed by Tribology group UAM A in Mexico under the standards ASTM G-65 to dry conditions and ASTM G-105 to wet conditions. Because the standards use different parameters, it was necessary to equal these for both tests, as: load, sliding distance, lineal velocity in the contact point, particle size and hardness of the wheel. Steel used in this paper is employed in machine's components. With the objective of observing the benefit of boriding process on the AISI 8620 steel, was carried out the comparison of this steel with the basic material and the same with the boriding process. The wear rate is significantly less in wet condition than in dry condition; this for the reason that the water acts as a lubricant or refrigerant and hide the abrasion mechanisms. The surface of the boriding sample is very hard and consequently with little loss of the mass; to both tests presented a good behavior to abrasion.

Abstract: The austenitic stainless steel is excellent in corrosion resistance, toughness, and workability. But it is inferior to hardness and wear resistance. However, because it is not possible to stiffen by quenching, the development of the method of improving wear resistance is required. Recently, boriding has attracted extensive attention as surface stiffening processing of plain steel. In this research, the influence of processing temperature on the formation layer of SUS304 steel by B added fused salt bath was examined. Boriding were performed in molten borax which contained 4 mass%B at processing temperatures of 1123~1223 K (processing time of 1800 s). As a result of the examination, the hardness of the boriding layer becomes about 2000 HV when the processing temperature of 1223 K. Also the wear resistance too has improved remarkably. Furthermore, it was understood that the formation layer on the surface was FeB, and, additionally, consisted of compounds such as Fe, Cr, and B from the Vickers hardness and the analysis of the X-ray diffraction measurement.

Abstract: The austenitic stainless steel is excellent in corrosion resistance, toughness, and workability. But it is inferior to hardness and wear resistance. However, because it is not possible to stiffen by quenching, the development of the method of improving wear resistance is required. Recently, boriding has attracted extensive attention as surface stiffening processing of plain steel. In this research, the influence of processing temperature on the formation layer of SUS304 steel by B added fused salt bath was examined. Boriding were performed in molten borax which contained 4 massB at processing temperatures of 1123~1223 K (processing time of 1800 s). As a result of the examination, the hardness of the boriding layer becomes about 2000 HV when the processing temperature of 1223 K. Also the wear resistance too has improved remarkably. Furthermore, it was understood that the formation layer on the surface was FeB, and, additionally, consisted of compounds such as Fe, Cr, and B from the Vickers hardness and the analysis of the Xray diffraction measurement.

Abstract: Boriding being a thermochemical process is widely used for boridetype coating. This process generally results in the formation of FeB and Fe2B needle-like microstructure at the surface. The presence of iron borides formed on the steels surfaces increases largely their hardness (up to 2000 HV), wear resistance, corrosion resistance and heat resistance [1÷3]. The main disadvantage of boriding is the brittleness of borides, especially of FeB phase. There are several factors that cause the brittleness of borided layers: first, the FeB and Fe2B have high hardness; second, a large hardness gradient exists between the borided layer and the substrate. The frequent symptoms of this defect are: microcracks of these layers, chipping and spalling. The literature data [4, 5] show, that the following factors influence the brittleness of borides: case depth of the layer, hardness, phase composition, internal stresses and chemical composition of borided steel. Many methods can lessen the brittleness of the boride layers. Three main are: obtaining a single-phase Fe2B layer [1÷3], the production of multicomponent and complex borided layers [6÷9] and laser heat treatment (LHT) after boriding [10÷12]. The one of these methods is boriding of previously carburized steel [7÷9]. This process called borocarburizing aims at forming a transition layer between the borided layer and the substrate. The transition area has a relatively higher carbon concentration and higher hardness, what reduces the hardness gradient of the iron borides to the substrate. Hence the brittleness of borided layer is lessened. The borocarburized layers are characterized by improved abrasive wear resistance and increased low-cycle fatigue strength in comparison with typical borided layers formed on medium-carbon steel [7, 9]. Although the fracture toughness of typical borided layers is well known, there is not information referring this property in case of borocarburized layers. In this paper the fracture toughness of borided and borocarburized layer has been compared. The wellknown adhesion tests prescribed by the VDI 3198 norm [13] were carried out in order to cohesion determination of examined layers.

Abstract: Astudy of the aspects of forming highly resistant coatings in the surface zone of tool steels and solid carbide inserts by a dual-stage method was made. At the first stage of the method, pure Ta or Nb coatings were electrolytically deposited on samples of tool steel and solid carbide insert in a molten salt bath containing Ta and Nb fluorides. At the second stage, the electrically deposited coating of Ta (Nb) was subjected to carburizing or boriding to form carbide (TaC, NbC) or boride (TaB, NbB) cladding layers. It has been found that formation of cladding layers consisting of highly resistant carbide (boride) phases in the surface zone of the samples under study is determined by the carbon (boron) atoms outsourcing. Machining operations tests carried out to check the durability of cutting tool inserts covered with TaC deposited by the invented method, have demonstrated efficiency of these inserts for finishing cuts. The invented method has been found to be promising for extending the service life of parts in the mining-metallurgical and machine-building equipment.

Abstract: Two different approaches are used in the evaluation of Fe2B growth and its kinetics over the surface of AISI 1018 steel. The first approach considers a diffusion model based on the mass balance at the growing Fe2B/substrate interface. In the second approach, the method of dimensional analysis was applied to obtain an expression for the boride layer thickness as a function of dependence parameters involved in the boriding process. The Fe2B layers were formed by the paste boriding process at temperatures of 1 123 to 1 273 K with 2, 4, 6, and 8 h of exposure using a boron carbide paste thickness of 4 mm over the surface of the steel. Another set of boriding temperatures with 5 h of exposure were used on the surface of the steel to compare the experimental values of Fe2B layer thicknesses with the results obtained by both diffusion models. The predicted values showed good agreement with the experimental boride layer thicknesses achieved in this work.