Hard TiB2 Research Articles

Optimization and characterization of boric acid powder mixed electrical discharge machining of Ti-6Al-4V ELI

The powder mixed electrical discharge machining (PMEDM) process is used for enhancing machining efficiency and improving the surface characteristics of the workpiece compared to normal EDM. The present study evaluates the effect of boric acid powder mixed in deionized water in PMEDM of Ti-6Al-4V ELI (extra low interstitial). The PMEDM process is assessed by evaluating material removal rate (MRR) and surface roughness (SR) at varying powder concentration (PC), current and pulse duration ( Ton). Boric acid PMEDM exhibits advantageous for both MRR and SR, where MRR increases and SR decreases with an increase in PC. To simultaneously achieve higher MRR and lower SR, the grey-fuzzy logic method is employed. Initially, the raw input data is normalized into grey numbers and a single index is obtained through grey relational analysis. Subsequently, triangular membership functions are assigned to the inputs and output. Fuzzy logic rules are then formulated, and grey fuzzy relational grade (GFRG) is calculated for each condition. The optimum condition (GFRG = 0.787) is attained at 15 g/l PC, 9 A current and 106 µs Ton, resulting in a 63% improvement compared to the initial condition. At the optimum condition, MRR increased by 145% and SR decreased by 29% compared to the initial condition. The effect of boric acid in PMEDM can be visualized through the formation of smooth surfaces, exhibiting reduced SR, smaller and shallower craters, and fewer debris and globules. Additionally, the boric acid PMEDM experiments resulted in the formation of a hard TiB phase on Ti-6Al-4V, thus improving its wear resistance.

Development of high hard TiB–TiB2 coatings on Ti implants for bio-tribological applications; applying Box-Behnken design and actual wear analyzing in simulated body fluids

This research focuses on the enhancement of the tribological behavior of commercial pure titanium (Cp-Ti) in a simulated body fluid (SBF) via surface reinforcement by titanium borides. The protective boride coatings were formed through the pack cementation process at two different temperatures (950 and 1050 °C) to create diverse hard compositions of TiB and TiB–TiB2 in the coating, with hardness of 1032 and 1291 Hv, respectively. The roughness and wettability of top surfaces were evaluated before the tribology studies due to their impacts on the tribology behavior. Box-Behnken design (BBD) was applied to investigate the effects of the wear parameters in dry and SBF environments. The duration of the wear tests was 53, 35, and 26 min for low, medium, and high speed. It was found that the abrasion wear type was dominant at the beginning of sliding, and then changed to the plastic deformation in the dry conditions, while there is no sign of the abrasion and adhesion wear features at the surface of the reinforced samples abraded in the SBF solution. Results confirmed a high coincidence between BBD predictions and actual findings. The released debris from the coatings was also investigated to find origins. Results showed that majority of the debris in the SBF solution belonged to the calcium phosphate particles demonstrating the bioactivity of the TiB–TiB2 coatings. According to findings, hard TiB–TiB2 coatings could significantly improve the tribological behavior of the Ti implants, which could in turn result in expanding the biological application of Cp-Ti.

Tribological Properties of Hard TiB2 Thin Films Prepared at Low Temperatures Using HiPIMS

Magnetron-sputtered WS2 composite thin films are solid lubricants with excellent performances. However, the low hardness of the WS2 thin films necessitates the further improvement of their wear resistance. For this purpose, an effective strategy is to alternately deposit or code posit WS2 and a hard phase, such as TiB2, to form hard lubricant thin films. Herein, a TiB2 thin film was prepared under the same conditions as those used for depositing the WS2 thin film with a dense structure and excellent tribological properties. Because of the high deposition energy of high-power impulse magnetron sputtering (HiPIMS), the TiB2 thin film possesses a dense structure and leather-like flat surface (hardness = 24.17 GPa). The friction coefficient of the film under different loads ranges between 0.6 and 0.8. The wear rate of the thin film increases with load, mainly because of fatigue wear and abrasive wear. Under high loads, obvious furrow-like wear marks are observed. At different sliding frequencies, except 8 Hz, the friction coefficient of the film ranges from 0.6 to 0.8. The main wear mode is fatigue wear, particularly at increasing sliding frequencies. Although the film possesses a relatively high friction coefficient, its wear resistance is excellent (minimum wear rate = 1.96 × 10−6 mm3/(N·m)).

Controlled Synthesis of TiB2-TiC Composite: Substantiation of the Homogenizing Joule Thermostatting Efficiency and Improvement of SHS-Compaction Technology in a Vacuum

This research aims to improve and substantiate the efficiency of homogenization heat-stabilizing Joule heating on ceramic-matrix composites of TiB2-TiC system with a 2:1 component ratio during its synthesis. For this purpose, an improved technological approach is proposed, which is based on the known method of SHS-compacting but differs by the possibility of controlled Joule influence on the synthesis products, which is achieved by the use of a special electrothermal vacuum press-mold functioning according to a particular control algorithm. The task of controlled Joule heating is a compensation of the temperature gradient formed in the synthesized workpiece, which is solved by passing in it a direct current directed in line with the vector of propagation of the combustion wave. An indicator of assessment of the degree of compensation of the noted temperature gradient is the Seebeck effect, excited between the upper and lower surface of the SHS workpiece, which should be brought to zero in the process of Joule thermostatting. It was experimentally revealed that compensation of the noted temperature gradient with heat released predominantly by electrically conductive and Joule-heated TiC grains leads to their softening, which contributes to more uniform compaction of the workpiece due to diffusion coalescence of these grains around prism-shaped hard TiB2 crystals. Such consolidation leads to a significant increase in the quality of structural packaging and a reduction in the number and volume of micropores, as a result of which the performance properties of the composite improve on average by 10–15 %.

Effect of TiB2 and GNP reinforcements on machinability in drilling of Al7075/TiB2/GNP hybrid composites produced by powder metallurgy

In this study, it has been aimed to investigate the machinability performances by drilling by producing Al7075 matrix hybrid composite samples with graphenenanoplate (GNP) and titaniumdiboride (TiB2) reinforced at different rates by powder metallurgy. The impacts of GNP and TiB2 reinforcing materials on the cutting parameters and wear behavior of the cutting tool have been examined and discussed. As a result of the drilling tests which are carried out by applying different cutting parameters, it was observed that GNP additive has positive impact on the cutting forces, surface roughness, and hole quality in general. As a result of the machining experiments, the lowest cutting force was obtained as 150 N at a feed rate of 0.100 mm/rev and a cutting speed of 60 m/min in the 1% GNP reinforced sample. The minimum roughness value was obtained as 0.886 micron at 60 m/min cutting speed in the 1% GNP reinforced sample. The minimum deviations from cylindricality and circularity were also measured as 0.03 and 8.005 mm from the 1% GNP reinforced sample. While the lubricating effect was low with a GNP ratio of 0.5%, the abrasive effect was observed more with a GNP ratio of 1.5%. While GNP supplementation decreased the diameter deviation and cylindrical deviation values, it increased the perpendicularity deviation values. In general, swarf chip formation occurred with a small amount of flank wear on the cutting tools. While hard TiB2 reinforcement particles in the composite structure were effective in flank wear, the most important cause of chip formation was the presence of ductile aluminum matrix and relatively low cutting speeds. When the entire experimental study was evaluated, it was evaluated that the solid lubricant property of the GNP reinforcement material was effective at the most 1% GNP reinforcement rate.

Exploring the intricacies of machine learning-based optimization of electric discharge machining on squeeze cast TiB2/AA6061 composites: Insights from morphological, and microstructural aspects in the surface structure analysis of recast layer formation and worn-out analysis

Aluminium (Al) Alloy-6061/TiB2 was developed with Squeeze casting while varying composite quantities with titanium diboride (TiB2). The metallographic structure of the composite was investigated using EDS and scanning electron microscopy (SEM). The machining of developed composite is challenging with the conventional methods due to higher tool wear and surface roughness (Ra). This study analyses the output responses, and machinability of TiB2 of 15% volume reinforced AA6061 composites using Electrical Discharge Machining (EDM). The EDM operation variables such as current, pulse on time, and voltage gap were utilized to examine material removal rate (MRR), tool wear rate (TWR) and Ra employing Box–Behnken design of experiments. The MRR, TWR and Ra data acquired from various experiments were optimized considering single and multiple objectives by a hybrid approach. Machine learning (ML) was applied to predict responses using linear regression (LR), decision tree (DT) and random forest (RF). The samples' recast layer was examined using SEM, and the thickness of the recast layer was also documented. The Al6061 alloy's SEM micrographs reveal deep equiaxed dimples on its fracture surface, indicating a high level of plastic deformation before failure. TiB2 is evenly distributed as darker particles in the Al-matrix alloy with no directional-orientation. The Al6061-15 wt% TiB2 composites' fracture surfaces display deep dimples, ductile-fracture for Al6061 alloy due to higher plastic deformation, and cleavage facets in some areas. The aluminum alloy's wear pattern depicts long, extensive ploughing grooves with short cracks parallel to the sliding direction at the grooves' bottom. SEM micrographs in recast-layer formation have reported that molten metal ligaments break into droplets during flushing, exposing fresh surfaces. The aluminum alloy's groove width is larger compared to the composites. Thus, it can be observed that the wear tracks on the base Al6061 alloy are larger and deeper in comparison to the Al- 15 wt% TiB2 surface composites due to the presence of hard TiB2 particles. Also, the recast layer may be advantageous due to its wear-resistant properties. TiB2 has importance in an industry where components slide with each other it is used in disc brakes in automobiles. Compared to industry standards, single-objective optimization considerably enhanced the outcomes: MRR increased by 10.61%, TWR enriched by 25.91%, and Ra increased by 17.60%. According to an ANOVA, peak current contributed 87.88%, 98.18%, and 95.80% respectively to MRR, TWR, and Ra. It is requisite to investigate multi-objective optimization for EDM of Al6061-15 wt% TiB2 composites' owing to the diverse optimal factor combinations for responses. Ra was slightly increased by 1.14% due to simultaneous optimization utilizing hybrid techniques with Equal and Entropy weights, which diminished TWR by 11.74% and increased MRR by 11.66%. ML, particularly DT, improves machining performance by assisting productivity, durability, and cost-efficiency under changeable circumstances and raising forthcoming study possibilities.

Spraying wear-resistant coatings from clad powders TiB2/Ti and HfB2/Ti

The present work considers the results on synthesis of composite clad powder systems with the “core-shell” type of structure for spraying wear-resistant metal-ceramic coatings. Powders of highly hard TiB2 and HfB2 borides were used as a core for the synthesis of a composite powder, and titanium was used to create coating on their surface. The cladding layer is synthesized by the iodine transport method. Powder cladding uses the method of detecting one component on another gas transport path, the agent of which is contact iodine. The deposition of composite clad powders of the TiB2 /Ti and HfB2 /Ti systems is implemented by the microplasma method, which, in contrast to the classical plasma deposition, makes it possible to dissolve transformations in composite powders due to thermal action. In the study of transverse microsections of sprayed coatings, it was found that during microplasma spraying, titanium is saturated with oxygen, forming a titanium dioxide phase, as a result of which the clad composite powder of systems TiB2 /Ti and HfB2 /Ti are converted into coatings from systems TiB2 (TiB)/Ti(TiO2 ) and HfB2 /Ti(TiO2 ). Features of the composition in terms of coating thickness were revealed. The study of hardness shows that the integral value of microhardness for a coating based on titanium diboride is 1300 HV. Coating based on hafnium diboride has integral microhardness of about 1600 HV. When checking the wear resistance, pairs with TiB2 (TiB)/Ti(TiO2 ) and HfB2 /Ti(TiO2 ) coatings were mated with a counterbody from the 45Kh sample without coatings and together with each other. Despite the lower microhardness, the most wear-resistant is coating of TiB2 (TiB)/Ti(TiO2 ) system.

Effect of particle morphology on fatigue crack propagation mechanism of TiB2-reinforced steel matrix composites

Fatigue crack growth mechanisms of as-cast and hot-rolled TiB2-reinforced steel matrix composites (SMCs) fabricated by eutectic solidification are systematically investigated through in-situ scanning electron microscopy (SEM) fatigue experiment system. The experiment results show that the as-cast SMC exhibits a relatively superior fatigue crack growth resistance with respect to the hot-rolled SMC. A lower FCGR at the low and intermediate stress intensity factor (ΔK) range in as-cast SMC is found, which is related to the TiB2 particle morphology. Hexagonal and rectangular primary particles have a high Young’s modulus and strong interfacial bonding, which inhibits the advancing of plastic deformation in front of the crack tip. Three-dimensional interconnected eutectic particle phases composed of dendrites can produce a hardening effect at crack tip and restrain the generation of plastic deformation in this morphology region. The stress-strain field in front of the crack tip is changed by the hard TiB2 particles, which leads to the deflection of the crack path. Hence, the tortuous crack path created by facing these particles causes reduction in the effective driving force of the crack tip and slows the FCGR. The net mismatch between the surfaces lead to premature contact and roughness-induced crack closure further reducing the FCGR. In comparison, large number of hot-rolled micro-cracks in the hot-rolled SMC are detrimental to fatigue crack growth resistance through the coalesce mechanism of micro-cracks, thereby accelerating the FCGR.

Experimental Investigation to Confirm the Presence of TiB2 Reinforcements in the Matrix and Effect of Artificial Aging on Hardness and Tensile Properties of Stir-Cast LM4-TiB2 Composite

The present work focuses on the effect of multistage solution heat treatment (MSHT) and artificial aging on two-stage stir-cast LM4 + TiB2 (1, 2, and 3 wt.%) composites on the mechanical properties as compared to as-cast and single-stage solution heat-treated (SSHT) composites. Two novel tests, viz. the confirmation hardness test and the chemical analysis test, were performed to ensure the soundness of the casting and uniform distribution of TiB2 within the matrix. Samples subjected to MSHT + aging at 100–200 °C displayed the highest hardness and UTS values compared to as-cast and SSHT + aging at 100–200 °C samples. Compared to as-cast alloy, peak-aged samples of 1–3 wt.% (MSHT + aging at 100 °C), hardness values improved from 107–150%, and UTS values improved from 47–68%. The presence of metastable phases (θ′-Al2Cu and θ″-Al3Cu) and of hard TiB2 particles are the reason for the improvement in the properties. Peak aged LM4 + 3 wt.% TiB2 composite displayed the highest hardness of 175 VHN and UTS of 251 MPa. Fracture analysis of the LM4 alloy showed dimple rupture, and its composites revealed quasi-cleavage fracture. Based on the overall results, the inclusion of TiB2, MSHT, and artificial aging treatment on the LM4 alloy significantly influenced the composites’ mechanical properties.

Unique opportunities for microstructure engineering via trace B4C addition to Ti-6Al-4V through laser powder bed fusion process: As-built and heat-treated scenarios

This research study examines the role of minor B 4 C addition (0.2 wt%) in improving the mechanical properties of the laser powder bed fusion (L-PBF) fabricated Ti-6Al-4V (Ti64) alloy in the as-built and heat-treated conditions. The fabricated titanium matrix composites (TMCs) were subjected to two different heat treatment scenarios, i.e., subtransus and supertransus, and were compared to the Ti64 counterparts exposed to the same thermal cycles. Both as-built and heat-treated Ti64 and TMC samples were characterized in terms of the grain structure, microstructure within the grains, and the size, morphology, volume fraction, and crystallographic orientation of the phases. The knowledge gained from microstructural investigations was correlated to the mechanical behavior of components, including compressive strength and ductility, microhardness, and scratch resistance. The governing strengthening mechanisms were identified, and the contribution of each mechanism in the overall yield strength was explored. Results revealed that TMCs possessed higher yield and ultimate compressive strengths than their Ti64 counterparts owing to the hard TiB needles homogeneously dispersed in the microstructure. However, except for the supertransus heat-treated condition, the TMCs showed slightly lower fracture strain than the Ti64 samples. The elimination of GB-α in the supertransus heat-treated TMC sample caused by the TiB needles led to a higher fracture strain than the corresponding Ti64 case. While the implemented heat treatment strategies could tailor the mechanical properties, the optimum thermal cycles for Ti64 were not necessarily applicable to TMC components.

Effect of titanium content on the microstructure and wear behavior of Fe(13-x)TixB7 (x=0-5) hardfacing alloy

In this study, the effects of titanium addition on microstructure, hardness, and wear rate of Fe(13-x)TixB7 (x = 0, 1, 2, 3 and 5) based hard surface alloy layers formed by gas tungsten arc (GTA) welding method were investigated. As a result of the microstructure studies and phase analysis, it was determined that the structures of the coating layers consisted of ?-Fe, ?Fe+Fe2B eutectic, ?-Fe+Fe2Ti eutectic and hard TiB2 phases. In the hard surface alloy layer, as the amount of titanium was increased, the TiB2 phase density formed in the system increased and it was observed that rod-like and long sharpedged phases formed from the equiaxed structure. As a result of wear tests performed at different loads, it was determined that the addition of titanium reduces the wear rates in the coating layers. In addition, scanning electron microscopy (SEM) images of the worn surfaces showed that the wear mechanisms were adhesive and oxidative.

Features of formation of the structure and proper-ties of surface layers reinforced with flux-cored wires based on the Fe-Ti-B-C system

In this work it was established that the structure of surfacing materials based on the Fe-Ti-B-C system depends on the brand of powders that were used for production of flux-cored electrodes. Two experimental electrodes of Fe-Ti-B-C were studied using two different brands of Ti powders. The brands were PHT and PTM, that are obtained by various methods. Microstructure of the coating with PHT Ti are characterized with the structure without hard TiB2 and TiC phases, which is a proof of the absence of “in-situ” synthesis reaction during FCAW surfacing. Such structure is also characterized by low hardness. Microstructure of the coating with PTM Ti consist of uniformly distributed hard phases in metal matrix, which is a proof of “in-situ” synthesis reaction during FCAW surfacing. The hardness of such structure is higher than the hardness of the previous example. The experiment shows that using powders of different brands can significantly affect the structure and physical and mechanical properties of the surfacing.

Selective Laser Melting of In Situ TiB/Ti6Al4V Composites: Formability, Microstructure Evolution and Mechanical Performance

In the present study, a series of in situ TiB/Ti6Al4V composites were fabricated using selective laser melting. The formability, microstructure evolution and mechanical properties of the as-built samples added with different contents of TiB2 were studied. It is found that the densification level is related to both the content of TiB2 and laser energy density. The added TiB2 reinforcement particle can spontaneously react with titanium and then form the TiB phase. The needle-like TiB phase tends to transform into dot-like particles with the decrease in energy density. Additionally, with the increase in TiB2 content, the TiB phase is coarsened due to the increased nucleation rate and more reactions. The grain morphology is found to largely depend on the translational speed of solid–fluid interface determined by the temperature gradient and cooling rate. Also, the microhardness of the as-built TiB/Ti6Al4V composites is obviously improved. More interestingly, as the energy density increases, the microhardness of the as-built TiB/Ti6Al4V composites firstly increases and then decreases due to the synergy of grain size and different morphologies and distribution of TiB phases. The wear resistance of TiB/Ti6Al4V composites is far superior to that of Ti6Al4V alloy owing to the increased microhardness resulted from the uniform distribution of the hard TiB phase in the matrix.

Fabrication and properties of in situ heterogeneous Cu/TiB2 composites with a harmonic structure

In situ heterogeneous Cu/TiB2 composites with a harmonic structure, where the soft domains of pure Cu are completely surrounded by the hard TiB2 enrichment domains, were fabricated by hot pressing. By controlling the ratio of the Cu powders during ball milling and vibrational blending, composites with different degrees of heterogeneity were obtained. The results of tensile testing show that the composites with proper degrees of heterogeneity possess an excellent combination of strength and ductility. In light of the loading–unloading–reloading tensile test and microstructure analysis results, the strengthening and toughening mechanisms of the heterogeneous composites are discussed. The high strength is attributed to back-stress hardening resulting from plastic incompatibility. The back-stress hardening associated with the strain partitioning results in an enhanced ductility.

Dry Sliding Friction and Wear Behaviour of AA6082-TiB2 in Situ Composites

In this study a composite with AA6082 as the matrix and TiB2 as the reinforcement has been fabricated by in situ method. The effect of TiB2 addition on the mechanical and tribological behaviour has been investigated. The purpose of the study is to improve the friction and wear properties of AA6082 so as to widen the engineering applications of the alloy. The reinforcement varied as (0, 3, 6, 9 wt%). The mechanical characteristics such as hardness and density improved with the addition of the reinforcement particles. The microhardness also shows slight increase in its value with increase in reaction time. The microstructural examination depicted grain refinement of the cast composites with increase in reinforcement. The wear resistance also increases with the addition of the reinforcement. The coefficient of friction exhibited an increasing trend and thereafter it decreased with increasing reinforcement at lower load. However, at higher load, an increase in the coefficient of friction is observed with an increase in reinforcement. SEM and EDS analysis revealed distinct wear mechanisms for different composites and different loads. The present study reveals that with addition of hard TiB2 particles the mechanical and tribological of AA6082 are improved. The results suggest that the developed composite material could be a potential material for various engineering applications.

Mechanical and Wear Behaviour of Hot-Pressed 304 stainless Steel Matrix Composites Containing TiB2 Particles

In the present article, mechanical and wear behaviour of hot-pressed 304 stainless steel matrix composites containing 2 and 4 vol% TiB2 particles was investigated. A density of over 92% was achieved at optimum hot-pressing temperature and TiB2 particles’ content. Microhardness and yield strength of the composites were found to be improved remarkably as compared to their unreinforced counterpart. The enhancement of mechanical properties of the composites was discussed in light of their microstructural aspects and different possible strengthening mechanism models. Taylor strengthening was found to be dominant strengthening mechanism as compared to Orowan strengthening and load-bearing effect. Dry sliding wear behaviour was also investigated under load of 35 N at sliding speed 0.3 m/s. The wear resistance of the composites was found to be improved owing to uniform distribution of hard TiB2 particles. Based on our findings, it was concluded that processing parameters and amount of TiB2 have significant influence on mechanical and wear behaviour of steel matrix composites.

Corrosion behavior of stir-cast Al–TiB2 metal matrix composites

Abstract The present study evaluates the corrosion behavior of Al–TiB2 metal matrix composites in 3.5% NaCl solution. Composites are fabricated using stir-casting with varying wt.% of TiB2. Composite surfaces are characterized using scanning electron microscopy (SEM) images. Micro-hardness values of composites are obtained using a Vicker's micro-hardness tester. The hardness of the base matrix is enhanced due to the incorporation of hard TiB2 phase. Corrosion characteristics of composites are investigated using potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Corrosion resistance of composites is estimated from the parameters such as corrosion potential, corrosion current, linear polarization resistance etc. Corrosion resistance of the base alloy improves due to incorporation of TiB2 but only up to a certain amount of TiB2 phase in the matrix. The composite with 1 wt.% TiB2 shows the highest corrosion resistance. Corroded surfaces are studied using SEM images that reveal localized pitting corrosion on composite surfaces.

Effect of TiB2 addition on wear behavior of (AlCrFeMnV)90Bi10 high entropy alloy composite

Abstract The present investigation reports development of a novel self-lubricating high entropy alloy composite; AlCrFeMnV BCC alloy as a matrix along with Bi and TiB2 as a solid lubricants, synthesized using spark plasma sintering. In particular, synergistic effect of soft Bi and hard TiB2 on tribological behavior of the HEA composite has been correlated with microstructure. TiB2 addition leads to 85% decrease in wear rate compared to base alloy. Exceptional decrease in wear rate is due to high hardness of TiB2 and uniformly dispersed Bi particles, which undergo softening and melting during sliding acting as a lubricating film between the sliding bodies. Computational modeling of contact stress and temperature during wear was performed to study surface and subsurface deformation and temperature rise during wear.

Effect of tool nose radius and tool wear on residual stresses distribution while turning in situ TiB2/7050 Al metal matrix composites

In situ TiB2/7050 Al matrix composite is a new kind of particle reinforced metal matrix composite. With in situ synthesis method, a better adhesion at interfaces is achieved and hence improves mechanical properties. However, due to the presence of hard TiB2 ceramic particles, the tool wear problem is severer while machining TiB2/7050 Al composites compared with traditional metallic alloy. In order to have a deeper understanding of the residuals stress distribution during machining metal matrix composites, this paper investigates the effect of tool nose radius and tool wear on the residual stress distribution during turning TiB2/7050 Al composites. Four CBN tools with different tool nose radius (0.4, 0.6, 0.8, and 1.0 mm) are used. The cutting force and residual stress distribution beneath the machined surface have been analyzed when the CBN tools are new or worn (0.26 mm VB). The results show that the residual compressive stress distribution is always obtained on the machined surface and subsurface no matter the tools are new or worn. The larger tool nose radius causes the increase of cutting force, lower surface residual compressive stress, and deeper residual stress penetration layer. As the tool wear, the location of maximum residual compressive stress transfers from the machined surface to the deeper subsurface. Compared with the tool nose radius, the tool wear has more significant influence on the cutting force and residual stress distribution.

Metallurgical features of direct laser-deposited Ti6Al4V with trace boron

The variation in the metallurgical characteristics, in terms of microstructure and microhardness, of direct laser deposited Ti6Al4V premixed with trace boron (0.04 wt%) was investigated. A significant improvement in the clad hardness from 390 to 450 HV in Ti6Al4V deposit to 510–600 HV in Ti6Al4V0.04B clad was observed. This was attributed to not only the fine α-Ti laths but also the presence of very hard TiB precipitates formed in the latter sample when compared to the martensitic α′-Ti formed in the former specimen. The high cooling rates experienced during deposition produced an extremely fine and even distribution of TiB.