Thermal fatigue failure is one of the main factors affecting the service life of hot work die steel. Achieving excellent thermal fatigue resistance for hot working die steels can benefit the industry ...economically. In this work, (TiC + TiB2)/Al master alloys were used to add TiC–TiB2 nanoparticles into high-Cr die steels, which achieves microstructure manipulation and obtains excellent thermal fatigue resistance and strength-plastic combination. The results showed that after being manipulated by 0.02 wt% TiC–TiB2 nanoparticles, the surface oxidation zone of the high-Cr die steel after different thermal fatigue cycles is reduced than high-Cr die steel without manipulation. TiC–TiB2 nanoparticles effectively refined the heat-treated microstructure of high-Cr die steel, promoting the Cr element and alloy carbides being more uniformly distributed in the matrix, which prevents the occurrence of oxidative pitting and conducive to the formation of a dense and uniform Cr2O3 oxide layer, and further preventing the initiation of thermal fatigue cracks. Moreover, these finer and more uniformly distributed precipitates in TiC–TiB2 nanoparticles manipulated high-Cr die steels will promote stress dispersion and hinder thermal fatigue crack propagation. This work provides a promising avenue for the design of low-cost, high-performance, and long-life die steels for industrial applications.
•The microstructure has been manipulated with traces TiC–TiB2.•Thermal fatigue cracks initiation are closely correlated to surface oxidative erosion.•Nanoparticle-reinforced steels have better thermal fatigue resistance.
Laser cladding process, an efficient surface remanufacturing method, has become a research hotspot in recent years. Herein, in situ titanium carbide (TiC) and titanium diboride (TiB2) reinforced ...composite coatings were fabricated on the surface of damaged carbon steel to improve the hardness and wear resistance of remanufactured parts. Effects of addition of 5B4C and 15Ti (in wt.%) powder on morphology, phase composition, microstructure, and mechanical properties of specimens were comprehensively investigated. Results revealed that milled groove could be effectively filled with composite coating, which formed good metallurgical bonding with the substrate. Furthermore, sequentially precipitated in situ synthesized phases including TiC, TiB2, Cr3C2, Fe2B, and Fe3C in composite coating could continuously increase nucleation sites and further refine grains. Moreover, uniformly distributed reinforcements effectively weakened the directivity of heat flow during solidification process and promoted columnar to equiaxed transition. Mechanical properties illustrate that micro-hardness of composite coating with 961.94 HV0.3 is 4.14 and 5.04 times, and corresponding volume loss is 7.8 and 2.8 less than those of 316 L coating and standard 45 steel, respectively. This study indicates that in situ formed ceramics reinforced composite coating can act as an ideal candidate for remanufacturing damaged parts, and further improve their wear resistance.
In order to improve the surface mechanical performance of Ti-6Al-4V alloy, in-situ TiC-TiB2 composite coating was deposited by tungsten inert gas (TIG) cladding process using Ti and B4C as precursor ...powder. Based on the available literature, SEM images of the blended precursor powder mixture and coating layer, electron probe micro analysis (EPMA) and corresponding XRD analysis of the produced coating, the formation mechanism of the present TiC-TiB2 composite coating during TIG cladding process was elucidated. The analysis shows that in the coating, TiB2 and TiB phases appeared as hexagonal or rectangular shape, whereas TiC as spherical shape within the matrix of unreacted Ti, Ti-6Al-4V alloy form the substrate and intermetallic phase like TiAl3 formed during the cladding process. The analysis also revealed that the TIG cladding processing current and scan speed have substantial effect on the coating morphology and the phases formed in the coating.
•In-situ TiC-TiB2 coating deposited on Ti-6Al-4V alloy by TIG cladding method with Ti and B4C powder.•Formation mechanism of TiC/TiB2 phases was elucidated during the process.•TiB2 and TiB phases formed as hexagonal/rectangular shape and TiC as spherical shape within matrix.•TIG current and scan speed have enormous effect on coating morphology and amount of phases formed.
NiAl–TiC–TiB2 intermetallic matrix composite coatings with various TiC–TiB2 contents were fabricated by depositing self-propagating high-temperature synthesized (SHS) NiAl–TiC–TiB2 powders using ...atmospheric plasma spraying (APS) technique. The preparation process was carefully investigated and the effects of TiC–TiB2 contents on the physical and chemical properties of the composite coating were studied. Results indicate that SHS synthesized NiAl–TiC–TiB2 intermetallic matrix materials show high purity. The TiC–TiB2 particles are well dispersed in the NiAl matrix. There is no obvious oxidation in the composite coating during the APS process. With an increase in TiC–TiB2 contents, the hardness of NiAl–TiC–TiB2 composite coating is increased, while the thermal expansion coefficient (TEC) of the coating is decreased. NiAl–TiC–TiB2 intermetallic matrix composite coating with moderate TiC–TiB2 content shows the best corrosion resistance. Few TiC–TiB2 particles in NiAl promote the formation of the continuous Al2O3 film without destroying the integrity of the film improving the corrosion resistance of the coating.
Forging and welding are common necessary procedures for AA6××× alloys, and recrystallization is an inevitable process. However, it is still difficult to realize the control of the recrystallization ...behavior, while realizing the strengthening of mechanical properties of the base metal and welded joint. In this study, we overcome this problem through 0.5 wt% TiC–TiB2 nanoparticles, and fully reveal the influence of the nanoparticles on the recrystallization behavior of the base metal and nugget zone of a friction-stir-welded (FSW)-ed joint from the perspectives of dislocation rearrangement and grain boundary motion. The strengthening mechanisms of the base metal and FSW-ed joint are clarified. The recrystallization driving force of the base metal and nugget zone was increased. Dislocations with a higher density rearranged and formed more grain boundaries in the nugget zone. Besides, nanoparticles distributed on the grain boundaries restrained the vanishing of low-angle grain boundaries. The nugget zone microstructures were refined from 3.1 to 2.3 μm, and the recrystallization ratio was increased from 7.2% to 10.4% at 800 rpm. The grains in the nugget zone were refined from 2.2 to 1.9 μm, and the recrystallization ratio was increased from 16.1% to 18.4% at 1200 rpm. The promoted recrystallization in the nugget zone accelerated the release of stress. Nanoparticles weakened the precipitate coarsening in the nugget zone. After strengthening, the ultimate tensile strength and plastic strain of the FSW-ed joint at 800 rpm were increased by 4.7% and 18.8%, respectively. This study provides new approaches for a systematic microstructure evolution control in FSW-ed 6061 Al alloys.
•Trace nanoparticles double the recrystallization driving force of base metal.•More dislocation tangles promoted recrystallization of nugget zone.•Nanoparticle also inhibited grain coarsening of nugget zone.•Precipitate coarsening in the nugget zone was weakened.•FSW-ed joint softening was alleviated and the mechanical properties were enhanced.
Herein, the effects of dual‐phased TiC–TiB2 nanoparticles on the microstructure and tensile properties of graphite ductile irons are investigated. Aluminum master alloys containing the TiC–TiB2 ...nanoparticles are utilized in the production of novel graphite ductile irons. It is found that the graphite nodules become finer with increased nodularity, smaller average diameter, and incremental amount per unit area. The thickness of ferritic and cementite layers in pearlite is reduced and the orientation becomes more regular. More ferrite is produced in the matrix after adding the nanoparticles. In tensile tests, the yield strength, tensile strength, and ductility are simultaneously improved. Also, it is determined that the cleavage and semicleavage fractures are transformed into ductile fractures after engaging the nanoparticles, which could be associated with more dimples and ductile risers being formed to promote the plastic deformation of the graphite ductile irons.
Novel graphite ductile irons are prepared using an aluminum master alloy containing TiC–TiB2 nanoparticles. It is found that the graphite nodules and pearlitic structure can be refined. The yield strength, tensile strength, and ductility are simultaneously enhanced after engaging the nanoparticles at room temperature and 150 °C.
TiC-TiB2 based composite coatings were fabricated on Ti-6Al-4V substrate by TIG cladding process using titanium (Ti), and boron carbide (B4C) preplaced powder mixture at different weight ratio ...(Ti:B4C = 5:1, 3:1 and 3:2). The effects of Ti/B4C powder ratio on the formation of the coating, their morphology and mechanical behavior namely the micro-hardness and the sliding abrasive wear characteristic were investigated for different processing conditions. The microstructural analysis revealed that for using lower B4C content (5Ti:B4C) in the precursor, at relatively lower current the formation of a uniform coating is possible, whereas for using higher B4C content (3Ti:2B4C) larger processing current was required to obtain a uniform coating with appropriate bonding. On the other side, the hardness and the wear resistance of the coatings are found much higher for higher B4C content in the precursor.
In this study, an innovative method, wherein trace in situ synthesized nano-(TiC+TiB2) particles are added forged H13 steel, was designed and used to manipulate its microstructure. This refined the ...grains and laths martensite, increased the retained austenite and carbides, and controlled the carbide segregation. Thus, the strength, plasticity, and toughness of the steel were simultaneously improved. Among the samples, the H13 steel, manipulated by 0.02 wt% nano-(TiC+TiB2) particles, exhibited the best mechanical properties. Its yield strength, tensile strength, elongation, unnotched impact toughness and U-notch impact toughness increased by 11.6%, 7.6%, 14.2%, 35.0% and 33.8%, respectively, and reached 1142 MPa, 1426 MPa, 16.9%, 449.3 J/cm2, and 41.39 J/cm2, respectively. The main strengthening mechanisms were grain boundary strengthening, dislocation strengthening and dispersion strengthening. This study provides a new method for the bonding between ceramic nanoparticles and steel and provides a novel idea for the development of high-performance and low-cost steel.
•The nano-(TiC+TiB2) particles (NPs) are beneficial to nucleation of γ-Fe/α-Fe.•The trace nano-(TiC+TiB2) particles inhibited carbide segregation of H13 steel.•More and fine carbides and austenite are yielded by adding trace nanoparticles.•The H13 steel with high comprehensive properties is prepared by adding trace NPs.
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•Properties of TiC (111)/TiB2 (0001) interfaces were investigated by first-principles.•The Wad of HS interfaces is larger than that of the CS and TS interfaces.•The C-HS-T interface ...exhibits the largest adhesive strength and stability.•The C-HS-T interface consists of polar covalent bonding and metallic bonding.
Properties of the TiC (111) surface, TiB2 (0001) surface, and TiC (111)/TiB2 (0001) interfaces were investigated by first-principles calculations. Additionally, the work of adhesion (Wad), interface energy (γint), and electronic structure of the TiC/TiB2 interfaces were studied. The calculated results show that the Wad of the hollow-stacked interfaces is larger than those of the center- and top-stacked interfaces. Among the interfaces of C/Ti-terminated hollow-stacked (C-HS-T), Ti/Ti-terminated hollow-stacked (Ti-HS-Ti), and Ti/B-terminated hollow-stacked (Ti-HS-B), the C-HS-T interface exhibits the largest Wad (11.43J/m2), the smallest interfacial separation d0 (1.208Å) and thus is the most stable. For the entire range of Ti chemical potential, the interfacial energy of the Ti-HS-Ti supercell was 1.04–4.59J/m2, while the interfacial energy was 0.54–0.58J/m2 and 0.45–0.49J/m2 for Ti-HS-B interface and the C-HS-T interface respectively. Furthermore, the C-HS-T interface consists of strong polar covalent bonding and weak metallic bonding, while the Ti-HS-B and the Ti-HS-Ti interface consists of primarily covalent and metallic bonding, respectively.
The properties of a TiC(0 1 0) surface, a TiB2(0 1 1¯ 0) surface, and TiC(0 1 0)/TiB2(0 1 1¯ 0) interfaces were investigated by first-principles calculations. The work of adhesion (Wad), the ...interface energy (γint), and the electronic structure of the interfaces were determined. The results show that the C-BS1-B1, C-TS-B2, and Ti-BS1-B1 interfaces are the most stable interfaces. Among all models, the C-TS-B2 interface is most stable and exhibits the highest Wad value (4.77J/m2) and the lowest γint value (1.12J/m2). All three stable interfaces exhibit strong covalent bonding due to the interfacial C-sp and B-sp orbital hybridization; the stable interfaces investigated in this study are as stable as the TiC(1 1 1)/TiB2(0 0 0 1) interface reported in a previous study.
