Small Carbide Research Articles

The wear resistance of micro spade drills and D-shaped tool materials

High-speed steel (HSS) is commonly used in producing micro-cutting tools due to its excellent abrasive wear resistance, especially under high rotational speeds and low thermal activation conditions. Numerous studies have focused on enhancing the microstructural properties of HSS further to improve the wear resistance of these micro tools. However, abrasive machining processes like grinding and lapping are employed during the manufacturing of micro tools such as spade drills, milling cutters, and taps. In these processes, controlling the wear rate is crucial, as it directly impacts the achievable material removal rate. Therefore, maintaining wear rate stability is more critical than only measuring the total amount of wear. In this context, this study aims to evaluate the wear of HSS with various microstructures using a variation of the pin-abrasion test (PAT). Pins of M3 class 2 (referred to as M3/2) HSS obtained from three different manufacturers were tested using SiC abrasive articles (320# mesh) under a constant load of 0.35 MPa and variable rotary speeds between 0.5 and 6.0 m/s. The materials were evaluated, and the type and quantity of primary carbides (MC and M6C) present in their microstructures were determined with the aid of scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). The results demonstrated a relationship between wear behavior and carbide size and distribution: materials with larger carbides with a non-uniform distribution exhibited greater wear rate instability. This implies that micro tools made from HSS should have a microstructure characterized by a uniform distribution of small carbide particles to ensure stability during fabrication. Additionally, a method for testing wear rate stability was proposed.

Effect of Heat Treatment on Microstructure and Properties of Powder Metallurgy High-Speed Steel Prepared by Hot Isostatic Pressing

The microstructure and properties of powder metallurgy high-speed steel prepared by hot isostatic pressing with different heat treatments have been studied. The microstructure, phase composition, effect of quenching and tempering parameters, fracture morphology, and mechanical properties of the sample are discussed in detail. The H-HSS sample presents the characteristics of the powder prior to the particle boundary and consists of carbide and ferrite, in which the carbides are fine and evenly dispersed without segregation. The bending strength and hardness of the H-HSS sample are 3112 MPa and 56.3 HRC, respectively. The Q-HSS sample is mainly composed of martensite, residual austenite, and carbides. With the increase in quenching temperature, the grain size of the matrix gradually grows, and the small carbide particles dissolve into the matrix, causing an increase in carbide size and a decrease in quantity. The bending strength and hardness of the Q-HSS sample quenched at 1210 °C achieve the maximum values of 3114 MPa and 68.8 HRC, respectively. After tempering, the martensite is transformed from a quenched lath shape to a needle shape, the residual austenite content decreases, and secondary carbides precipitate from the matrix, resulting in a secondary hardening. The T-HSS sample that is quenched at 1120 °C followed by tempering at 550 °C for 20 min has the best bending strength of 4355 MPa. However, the T-HSS sample that is quenched at 1240 °C followed by tempering at 550 °C for 120 min has a maximum hardness value of 69.5 HRC. The fracture mode of Q-HSS sample is brittle fracture, and the fracture mechanism is cleavage fracture. After tempering, the fracture mechanism of the T-HSS sample presents a transitional fracture mode between the cleavage fracture and micropore aggregation fracture.

Microstructure evolution, crack initiation and early growth of high-strength martensitic steels subjected to fatigue loading

Fatigue loading induced microstructure evolution featured by Fine Granular Area (FGA) in high-strength martensitic steels have close ties to the fatigue crack initiation and early growth, which are worthy of being investigated. On this issue, we conducted Very High Cycle Fatigue (VHCF), High Cycle Fatigue (HCF) and Low Cycle Fatigue (LCF) tests on three different types of specimens. Combined with post-mortem/quasi in-situ Scanning Electron Microscope (SEM) and Electron Back-Scattered Diffraction (EBSD) observations, as well as further Transmission Kikuchi Diffraction (TKD) and Transmission Electron Microscope (TEM) analyses, we captured two different types of microstructure evolution behaviors during the fatigue loading. One is the “dynamic precipitation”, a kind of phase transformation from martensitic matrix (BCC) to Nb- and Mo-rich small carbides (MC, M7C3) accelerated by repeated slight plastic deformation, whose formation does not rely on the stress concentration effect and also has no ties to the plastic strain localization and fatigue crack initiation. Another is the “local grain refinement” around those stress singularities (crack tip, or interior inclusion) generating substantial amounts of fine sub-grains in VHCF, HCF and LCF regimes, which can then promote fatigue crack initiation and early growth along sub-grain boundaries, fine/coarse grain boundaries and martensitic packet boundaries.

Effect of graphene and niobium carbide on microstructure and mechanical properties of Ni60 composite coatings prepared by laser cladding

Niobium carbide (NbC) is often used as a reinforcing phase to improve the mechanical properties of composite coatings, but its low thermal conductivity makes the flow of molten pool poor, and the cladding layer is prone to defects such as non-fusion and slag inclusion. Therefore, in this paper, Ni60–NbC composite coatings with different NbC content were prepared by laser cladding technology, and the 10 vol% graphene-20 vol% NbC-70 vol% Ni60 composite coatings were prepared under the optimal NbC component. The effects of the addition of NbC and graphene on the microstructure and microhardness of the coating were systematically discussed. The results show that the microhardness of 20 vol% NbC composite coating is increased from 680.1 HV to 882.9 HV compared with Ni60 coating without NbC.The composite coating with both NbC and graphene has a microhardness of up to 1048HV, which is 18% higher than the composite coating with only 20 vol% NbC. The mechanism is that the addition of graphene promotes the formation of chromium carbide (Cr23C6, Cr7C3) and increases the fluidity of the molten pool, which causes small niobium carbide particles to dissolve and recondense to form large particles. Large niobium carbide particles and chromium carbide jointly inhibit the excessive growth of other grains. This study provides a new idea for laser cladding of nickel-based composite coatings.

Research on the strengthening mechanism of Nb–Ti microalloyed ultra low carbon IF steel

Interstitial free (IF) steels are characterized by their interstitial free ferritic matrix due to addition of micro-alloying elements that draw carbon and nitrogen out of matrix to form carbonitrides. The IF steels typically have excellent deep drawing ability, certain mechanical strength, and high plastic deformation performance. In this paper, the microstructure evolution and carbides precipitation behavior during the hot rolling, cold rolling and annealing processes have been studied using both experimental and thermodynamic and kinetic modeling approaches. The strengthening mechanism of Nb–Ti microalloyed IF steel has been investigated. The results of the thermodynamic simulation indicates that the addition of Nb into Ti bearing IF steel promotes recrystallization at 900 °C, leading to fine recrystallized grains. Due to the recrystallization of austenite during the final rolling process, Nb–Ti microalloyed hot rolled plates exhibit finer grain size, fewer substructures, and lower dislocation density compared to the hot rolled plates containing only Ti. Building upon the initial fine and uniform structure, Nb–Ti microalloyed steel maintains a refined structure after undergoing cold rolling and annealing. The study of the carbides precipitation behavior suggests that TiN precipitates at high temperature above 1100 °C, while a substantial amount of (Nb,Ti)C and TiC precipitate at about 900 °C in Nb–Ti and Ti bearing steels, respectively. There is no significantly difference between the amount of carbides in steels hot deformed at 900 °C and in the hot rolled plates, indicating that the carbides mainly precipitate during the hot rolling process. There are negligible carbides precipitated during the coiling process at 600 °C. In Nb–Ti containing steel, Nb and Ti in solid solution are significantly reduced due to the large amount precipitation of (Nb,Ti)C during the final rolling process. The reduction of solid solution Nb effectively promotes the recrystallization of austenite. Therefore, the grains of hot-rolled, cold-rolled, and annealed strips are refined. In addition, there are more small size carbides in Nb–Ti bearing steel than that in Ti bearing steel. Therefore, the higher strength of Nb–Ti steel is mainly from the strengthening effect of grain refinement and carbides precipitation.

Optimizing austenite and carbide content in medium carbon silicon-rich steel: A stepped partitioning strategy and analysis of strengthening and ductility enhancement mechanisms

To achieve the objective of enhancing the yield strength (YS) of quenching and partitioning (Q&P) steel without compromising tensile strength and ductility, a stepped partitioning (SP) strategy was proposed for Q&P treatment on medium carbon silicon-rich steel. The optimized partitioning strategy involves a two-stage partitioning, the first stage is conducted at temperatures above the martensite start (Ms) temperature, followed by the second stage carried out at a lower temperature for an extended period, involving isothermal partitioning. Experimental results demonstrate that the SP strategy yields a significant quantity of small carbides, with an average size of 59.02 nm, along with 15.71 vol% of retained austenite (RA) and a carbon concentration of 1.01 wt% in RA. Furthermore, the SP-treated specimen exhibits a remarkable balance of strength and ductility, showcasing YS, ultimate tensile strength (UTS), and total elongation (TE) values reaching 1732 MPa, 2263 MPa, and 14.9%, respectively. The microstructure evolution during tensile deformation demonstrates that RA in short-duration conventional partitioning specimens underwent premature martensitic transformation during tensile deformation due to early deformation, whereas RA in long time conventional partitioning specimens was overstabilized due to highest C concentration, which resulted in poor enhancement of strengthening and ductility by TRIP effect. In contrast, the SP strategy achieved a reasonable stability of RA, resulting in a simultaneous increase of tensile strength and ductility. Simultaneously, an analysis of precipitation strengthening indicates that the abundance of fine carbides in martensite contributes to an increase in YS due to precipitation strengthening.

Combustion synthesized boron carbide powders by different organic carbon sources and microwave absorbing properties

AbstractBoron carbide powders were synthesized by combustion synthesis using organics chitosan, dextrin, cellulose, starch, and polyvinyl chloride (PVC) as carbon sources. The microwave absorbing properties of boron carbide powders synthesized by different carbon sources were investigated. The results showed that the powders synthesized using organic compounds containing Cl and N atoms as carbon sources have better absorbing properties. The peak value of reflection loss of boron carbide powder prepared with chitosan as carbon source is −46.41 dB at 2.1 mm thickness, with an effective absorption range of 9.21–12.30 GHz and an effective absorption bandwidth of 3.09 GHz. The small and uniform boron carbide grains and residual carbon with multiple morphologies enhance the interface polarization and electronic polarization in the material, which leads to multiple reflections and losses of the microwave. Additionally, the lattice defects and surface holes caused by Cl, N, and other atoms in chitosan and PVC increase the energy storage sites of the material, which makes the materials obtain excellent microwave absorbing properties. Boron carbides fabricated from an organic carbon source provide a potential for the preparation of high‐temperature resistant absorber.

Cryogenic Treatment of Martensitic Steels: Microstructural Fundamentals and Implications for Mechanical Properties and Wear and Corrosion Performance.

Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) formation of refined martensite coupled with an increased number of lattice defects, such as dislocations and twins, (iii) changes in the precipitation kinetics of nano-sized transient carbides during tempering, and (iv) an increase in the number of small globular carbides. These microstructural alterations are reflected in mechanical property improvements and better dimensional stability. A common consequence of cryogenic treatment is a significant increase in the wear resistance of steels. The current review deals with all of the mentioned microstructural changes as well as the variations in strength, toughness, wear performance, and corrosion resistance for a variety of iron alloys, such as carburising steels, hot work tool steels, bearing and eutectoid steels, and high-carbon and high-alloyed ledeburitic cold work tool steels.

STUDY ON THE ELECTRO-SPARK DEPOSITION PROPERTIES OF SKH51 TRANSITION COATING IN COMPOSITE GRADIENT COATING

Because of the limitation of deposition thickness in electro-spark deposition (ESD) technology, composite coatings are increasingly used in electro-spark deposition. The deposition quality of transition coating is the key to improve composite coating. The deposition quality of transition coating is the key to improve composite coating. SKH51 material belongs to tungsten and molybdenum based materials and a high-speed tool steel with small and homogenous carbide particles. It has high hardness and excellent thermal hardness. It has good impact toughness and wear resistance, and can be used as the intermediate layer of carbon steel material and super-hard cermet coating. Consequently, a gradient structure is established. In this article, SKH51 material was deposited on the surface of 45 steel by the electro-spark deposition. With orthogonal experimental design, 16 sets of deposition experiments were conducted by selecting 4 factors and 4 levels. The coating thickness, coating surface roughness and maximum wear width of 16 samples were measured and counted. SKH51 coating wear surface is mainly abrasive wear and oxidation corrosion which is due to dry friction resulting in high temperatures on the surface. Because the surface of SKH51 coating was rough, the wear mass was used, the error will be larger. So the wear mark width is used to compare the wear resistance of the samples. The normalization method was used to unify the different unit coating evaluation objectives into a single metric. Three groups of weighting factors were determined using the requirements of transition coatings for coating performance indicators. Then, it was substituted into the objective function, and each experimental group normalizes the parameters for calculation. As a result, three distinct sets of maximal goal functions were obtained. The optimal value of the objective function corresponded to the 12th sample group. Finally, the deposition process parameters of the 12th sample were regarded as the optimal process for the SKH51 transition coating.

Postprocessing of tungsten carbide‐nickel preforms fabricated via binder jetting of sintered‐agglomerated powder

AbstractThis study binder jets a tungsten carbide‐nickel (WC‐Ni) sintered‐agglomerated composite powder, and postprocesses the preforms using an initial sintering step followed by a hot isostatic pressing (HIP) step. The effects of sintering temperatures, sintering durations, and HIP temperatures on notable properties (e.g., porosity, microstructure, hardness, and oxidation behavior) are quantified. The highest average relative density produced in this study was 96.8%, and volumetric shrinkage of these coupons was about 64%. Microstructural characterization shows that the WC grains are homogenously distributed throughout the nickel matrix and grow to an average diameter of 1.6 (a 60% increase) during processing. X‐ray diffraction patterns indicate that no unwanted products were formed. Processed coupons achieved a maximum hardness of 54 Rockwell C, limited by their internal porosity. Oxidation tests result in the production of WO3 and NiWO4 at temperatures above 600°C. Methodologies and results from this study can be leveraged to additively manufacture highly dense, geometrically complex WC‐Ni parts with small carbide grains, low nickel content, desirable microstructure, and suitable functional properties.

Tailoring the strength and impact toughness of 9Cr1.5Mo1Co steel by optimizing ultra-fine martensite and retained austensite

The urgent demands for more excellent mechanical properties to meet higher steam temperatures for 9Cr steels have been the driving force behind the increasing research efforts on heat treatment. This paper presents a systematic study of the effect of the ultra-fine martensite (ultra-fine M) and retained austensite (RA) obtained by austempering process on mechanical properties are studied by experimental observations and phase-field simulation. The results demonstrate that austempering leads to the split and incompletion of martensitic transition, producing a mixed microstructure consisting of lathy martensite(lathy-M), ultrafine martensite(ultra-M), and retained austensite (RA). Due to the change of local chemical free energy and elastic strain energy caused by the redistribution of C element, two types (isothermal and athermal) of ultra-M form by spontaneous nucleation and interfacial migration during austempering with appropriate temperatures. Further tempering produces dispersed finer M23C6 precipitated at the interfaces of high-dislocated ultra-M than lathy-M. Meanwhile, RA decomposes into fine globular M23C6 and ferrite. Consequently, a larger amount of ultra-M and RA in quenched state results in smaller effective grain sizes and smaller carbides' average size, leading to the enhancement of precipitation strengthening, grain boundary strengthening, and impact toughness. This work establishes the potential for tailoring the strength and impact toughness of 9Cr1.5Mo1Co steel by optimizing the ultra-fine martensite and retained austensite using austempering process.

The properties of laser-clad coatings made of NiCrBSi alloy and recycled tungsten carbides

Tungsten carbide hard metals are one of the most known and successful powder metallurgical products used in environments where severe wear conditions prevail. Since tungsten belongs to the list of critical raw materials for the European Union (EU), its recycling is highly desirable. In this paper, recycled tungsten carbide powders fabricated by the zinc-reclaim process where mixed with NiCrBSi matrix and deposited with one-step laser cladding using a coaxial powder feeding on mild steel substrates. Prepared clads were tested in low-stress rubber wheel abrasion tests and compared with clads produced from commercial macrocrystalline (WC) and cast and crushed eutectoid WC/W2C reinforced clads. The results showed that recycled WC induced porosity in clads when produced with ‘production’ laser cladding parameters due to small carbide size resulting in poor wear performance. When laser-clad with lower heat input and productivity, pore-free clads with excellent wear performance were obtained.

Effect of Cr–Mo Addition on the Microstructure and Mechanical Properties of Medium‐Carbon Steel

Herein, the effects of Chromium–Molybdenum (Cr–Mo) addition on the microstructural evolution and mechanical properties of medium‐carbon steel after spheroidization annealing are systematically studied through scanning electron microscopy, electron backscatter diffraction, and tensile testing. Cr–Mo addition hinders the proeutectoid ferrite + pearlite transformation, thereby promoting the bainite transformation. Moreover, it refines the pearlite lamellar spacing as well as decreases the average carbide diameter, increases the number of carbides per unit area, and hinders ferrite recrystallization. Compared with those in the B1 steel annealed for 8 h, the size of carbides and their number per unit area in the CM1 steel are 30% lower and 2.2‐fold higher, respectively. Due to finer ferrite grains, smaller carbides, and a higher amount of carbides, the strength of steel improves, and the plasticity slightly reduces after Cr–Mo addition. After 2 h of annealing, the yield strengths of Cr–Mo steels are 77.5–109.5 MPa higher than those of base steels; the elongations are above 20%. The contributions of the strengthening mechanism of steel to the yield strength are as follows (from high to low): grain boundary, precipitation, solid solution, and dislocation strengthening.

Scanning precession electron diffraction study of carbide precipitation sequence in low alloy martensitic Cr-Mo-V tool steel

Precipitation of carbides after tempering of a medium carbon low alloyed Cr-Mo-V tool steel at 600°C was studied with scanning precession electron diffraction (SPED) in a transmission electron microscope (TEM). The precipitation sequence was evaluated by mapping the carbide distribution on carbon extraction replicas prepared from samples tempered for different durations of up to 24 h. The SPED results were supplemented by equilibrium calculations and energy dispersive x-ray spectroscopy (EDX) measurements in a TEM. It was found that ε-Fe2C precipitates within martensite laths during quenching via auto-tempering. During reheating to tempering temperature ε-Fe2C was dissolved and replaced by cementite, θ-M3C, which predominately form on martensite boundaries. It was further found that the small carbides in the early stage of tempering have predominantly a cubic MC structure, even if the V/Mo-ratio of the studied steel was only 0.12, and it is known from literature that V and Mo form cubic MC or hexagonal M2C carbides, respectively. Later during tempering more stable carbides, such as M7C3 and M23C6, also form, and it was concluded that the M7C3 form both by separate nucleation and precipitation on the cementite/matrix interface. The latter phenomenon was seen as particles with a core of cementite and a shell of M7C3 after 24 h of tempering.

Influence of hard phase size and spacing on the fatigue crack propagation in tool steels—Numerical simulation and experimental validation

AbstractIn this study, the fatigue crack growth rate in four different tool steel microstructures (hot rolled, powdermetallurgically processed, as‐cast, and carbide‐free) is experimentally measured and correlated with hard phase size and spacing, as well as with the roughness of the fracture surface that is created by crack kinking. Numerical simulations of crack growth in carbide‐containing microstructures are conducted and investigated. The results indicate a favorable influence of carbides with a larger size and higher degree of roundness, as they create the largest mean free path between the individual carbides at the same hard phase volume content. This facilitates the formation of a plastic zone in the matrix, which dissipates crack energy and reduces the effective stress intensity. In addition, the effect of crack kinking is increased at larger carbide sizes. Concerning practical application, the results suggest that a high degree of deformation is favorable regarding the fatigue growth resistance of tool steels, and that the use of powder metallurgically (PM) grades with small carbides is discouraged, if the lifetime of a tool is mainly controlled by the crack growth rate and not crack initiation.

Construction and regulation of molybdenum carbide/carbon hollow microtube composite and its supercapacitive behaviors

Crystal structure has an important effect on electrochemical performance. In this work, the molybdenum carbide/carbon hollow microtube (MoC/CHMT) composite is synthesized via carbonation of polydopamine encapsuled Mo-MOF material. Additionally, the crystal structure of molybdenum carbide in composite is controlled by adjusting the mass of dopamine in polymerization. The optimized MoC/CHMT shows the hollow microtubes morphology with the microtube diameter about 600–1100 nm and microtube wall thickness of 230–400 nm, constructed by small molybdenum carbide nanoparticles (about 1.2–1.5 nm) on the surface of nanoplates with thickness of ∼17 nm. Moreover, it could achieve a high specific capacitance of 513.5 F g−1 at a current density of 0.5 A g−1. The constructed YP50//MoC/CHMT device exhibits a maximum energy density of 17.5 Wh kg−1.

Influence of the Chemical Composition on the Solidification Path, Strengthening Mechanisms and Hardness of Ni-Cr-Si-Fe-B Self-Fluxing Alloys Obtained by Laser-Directed Energy Deposition

Nickel-based Ni-Cr-Si-B self-fluxing alloys are excellent candidates to replace cobalt-based alloys in aeronautical components. In this work, metal additive manufacturing by directed energy deposition using a laser beam (DED-LB, also known as LMD) and gas-atomized powders as a material feedstock is presented as a potential manufacturing route for the complex processing of these alloys. This research deals with the advanced material characterization of these alloys obtained by LMD and the study and understanding of their solidification paths and strengthening mechanisms. The as-built microstructure, the Vickers hardness at room temperature and at high temperatures, the nanoindentation hardness and elastic modulus of the main phases and precipitates, and the strengthening mechanisms were studied in bulk cylinders manufactured under different chemical composition grades and DED-LB/p process parameter sets (slow, normal, and fast deposition speeds), with the aim of determining the influence of the chemical composition in commercial Ni-Cr-Si-Fe-B alloys. The hardening of Ni-Cr-Si-Fe-B alloys obtained by LMD is a combination of the solid solution hardening of gamma nickel dendrites and eutectics and the contribution of the precipitation hardening of small chromium-rich carbides and hard borides evenly distributed in the as-built microstructure.

Microstructure Evolution and Fracture Mechanism of 55NiCrMoV7 Hot-Working Die Steel during High-Temperature Tensile

In this paper, through high-temperature tensile tests of 55NiCrMoV7 steel, high-temperature fracture behavior, microstructure evolution, and carbide distribution characteristics of both the thermal–mechanical coupling zone (fracture zone) and thermal stress zone (clamping zone) at different temperatures were studied. Intrinsic relationships between high-temperature fractures and carbide types, distribution and size were revealed, and evolution mechanisms of microstructure near cracks in 55NiCrMoV7 hot-working die steel during high-temperature deformation was clarified. Samples were stretched at different temperatures from 25 °C to 700 °C, and microscopic examinations were carried out using SEM and TEM. The results showed the following. With the increase in temperature, tensile strength and yield strength decreased, elongation and reduction of area increased, and fracture mode changed from brittle fracture to ductile fracture by transition temperature at about 400 °C. During high-temperature deformation, the grain dislocation density decreased and the tempered martensite decomposed, recovered, recrystallized, and then grain grew. M7C3 and M23C6 carbides precipitated and grew along the grain boundary, and a small amount of fine granular MC carbides was dispersed in the grain. The work done by the external force on the deformation zone would cause the temperature of it to be higher than the tensile temperature, which provides thermodynamic conditions for the redissolution of small carbides near the fracture zone and the grain growth of large carbides, resulting in a decrease in small carbides and increase in large carbides in thermal–mechanical coupling zones.

Failure behavior of a roller in automotive flywheel manufacturing

The failure behavior of a carburized 18CrNiMo7-6 steel roller from a roll forming mill used to manufacture automotive flywheels is investigated. Microstructural observations using optical and scanning electron microscopy are carried out, and the hardness determined using a Vickers hardness testing machine. The carburized layer is mainly comprised of fine tempered martensite, small carbides and retained austenite. The depth of the carburized layer around the roller groove is thinner than the required standard. The decrease in microhardness with increasing distance from the surface to the core is found to be due to the different carbon concentrations. However, a pronounced variation of the microhardness value is detected around the roller groove surface. This is related to the formation of an inhomogeneous microstructure during quenching after the carburizing process. The results indicate that the crack nucleates at the bottom surface of the roller and propagates along the direction vertical to the roll forming with a transgranular character.

Thermal diffusion of lithium implanted in small and large grain boron carbide

Boron carbide (B4C) is used as a neutron absorber for nuclear reactor control and installation protection in most types of reactors. When the B4C is irradiated in the reactor, large quantities of lithium and helium (up to about 1022 /cm3) are produced due to the neutron absorption reaction 10B (n, α) 7Li. This work aims at studying the Li diffusion in large grain size (20–50 µm) or small grain size (0.2 – 5 µm) B4C in the temperature range of 500–800 °C. Lithium was implanted in B4C samples at a fluence of 1014 ions/cm2 (maximum concentration of 54 at. ppm). The Li concentration profiles as a function of depth were obtained before and after each heat treatment by Time-Of-Flight Secondary Ionization Mass Spectrometry technique. A heterogeneous diffusion process was observed depending on the implantation depth. Considering diffusion in the non-damaged, bulk material beyond the implanted zone, the thermal diffusion of lithium into the grain boundaries was found to be about four orders of magnitude higher than into the grains.