In this study, (NiTi)100-xNbx (x = 5, 10, 15 wt%) ternary alloys with different Nb contents were synthesised in situ by directed energy deposition. Microstructure analysis shows that the ...(NiTi)100-xNbx ternary alloy possess a typical dendritic structure. With the increase of Nb content, eutectic regions were formed between Nb and NiTi alloy, and TiNb intermetallic compounds were segregated at the eutectic. The NiTiNb ternary alloy formed a good metallurgical bond with the substrate at all different Nb contents, and no cracks or unfused areas were observed. (NiTi)85Nb15 demonstrated excellent elasticity at varying loads, especially at a load of 800 mN, with a modulus of elasticity of only 57.37 GPa. Meanwhile, the in situ synthesised (NiTi)85Nb15 demonstrated excellent wear resistance compared to other materials, with a minimum specific wear rate of 0.96 ∗ 10−4 mm3/Nm. The superelasticity of NiTiNb alloys plays a role in alleviating the effect of normal loads during sliding wear, which is the key to improving wear resistance. The wear mechanism of NiTiNb ternary alloys is dominated by furrowing with a small amount of adhesive wear. This work reveals the influence of Nb element content on the microstructure and wear resistance of NiTi alloys, providing insights into in-situ alloying of NiTiNb ternary alloys through laser cladding. In future research, it is recommended to enhance the functional properties of NiTiNb ternary alloys, such as memory properties or superelasticity by heat treatment.
•The NiTiNb ternary alloy coatings were synthesised in situ via laser cladding.•The effects of Nb content on the wear resistance of NiTi alloys are revealed.•Provides new insights into the design and development of elastic wear-resistant coatings
Surface modification of Ti6Al4V alloy was conducted by additive manufacturing using ball-milling treated mixture of Ti and SiC powder particles. Two laser cladded layers of 90%Ti + 10%SiC and ...80%Ti + 20%SiC were deposited onto the Ti6Al4V substrate by single channel feeding system. This single channel feeding process using the ball-milled Ti+SiC powder mixture could offer a more homogeneous SiC distribution and thus cause a better fluidity during the laser cladding process. The microstructures of the cladded layers were analyzed by a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS). An X-ray diffraction (XRD) and a transmission electron microscope (TEM) were used for the determination of the phase products. The Vickers hardness of the cladded coatings was measured by H450-SVDH microhardness tester. Chemical reactions took place between the Ti and SiC particles in the composite layers, and the reaction products consisted of TiC and Ti5Si3. The average three-point bending strength of the sample from the Ti6Al4V substrate to the 80%Ti + 20%SiC coating was 515 MPa at room temperature. The 80%Ti + 20%SiC cladded layer increased the hardness of the Ti6Al4V matrix from 339.1 HV to 932.2 HV. As a consequence, the wear resistance was improved remarkably.
•Ti + SiC gradient coatings were laser cladded using ball-milled Ti and SiC powders.•In-situ reaction occurred between Ti and SiC, with the products of TiC and Ti5Si3.•Good bonding was achieved between the ceramic particles and metal substrate.•The hardness and wear resistance of matrix was improved remarkably by the coating.
•Thermal behavior and multicomponent mass transfer in direct laser deposition is simulated.•The solidification characteristics are obtained by transient thermal distribution.•The mechanism of ...multicomponent diffusion and convection are considered.•The composition profiles of Fe, C, Co and Cr are compared with the experimental results.•An unmixed zone is observed at the bottom of the melt pool.
During direct laser deposition process, rapid melting–solidification and addition of multicomponent powder lead to complex transport phenomena in the melt pool. The thermal behavior and mass transport significantly affect the solidified microstructure and properties of fabricated layer. In this paper, an improved 3D numerical model is proposed to simulate the heat transfer, fluid flow, solidification and multicomponent mass transport in direct laser deposition of Co-base alloy on steel. The solidification characteristics, including temperature gradient (G), solidification growth rate (R) and cooing rate (G×R), can be obtained by transient thermal distribution to predict the morphology and scale of the solidification microstructure. Multicomponent transport equation based on a mixture-averaged approach is combined with other conservation equations. The calculated melt pool geometry and the composition profiles of iron (Fe), carbon (C), cobalt (Co) and chromium (Cr) are compared with the experimental results. The results show that in the initial stage of direct laser deposition, the rapidly mixture of substrate material and added material occur in the melt pool and conduct plays an important role in heat transfer due to the low Peclet number. As the melt pool is developed, the heat and mass transfer in the melt pool are dominated by strong Marangoni convection. An unmixed zone is observed near the bottom of melt pool where the convection is frictionally dissipated due to the presence of solidified dendrites. Since the G/R decreases and G×R increases from the bottom to the top of the solidified track, the morphology of the microstructure changes from planar front to columnar dendrites to equiaxed dendrites and the grain size decreases.
Magnesium alloys are one of the most promising lightweight structural materials. However, the poor corrosion and wear resistance restrain their further application. As a kind of surface modification ...technique, laser cladding treatment is superior to others owing to its unique characteristics such as high efficiency and the metallurgical bonding between the coatings and substrates. In this paper, the laser cladding process and the effects of processing parameters, including laser power, scanning velocity, beam focal position, feeding ways of the material etc., are discussed in detail. The material systems preplaced on magnesium alloys are summarized. Except for the traditional metallic materials, novel ternary alloys, amorphous alloys and high entropy alloys (HEAs) are widely used and apparent advantages are exhibited. In terms of the problems existing in the laser cladding process of magnesium alloys, some potential solutions and the development tendency are reviewed.
•Laser cladding material systems on magnesium alloys are reviewed entirely.•Novel devices used for laser cladding are summarized.•The existing problems and the corresponding solutions are discussed.•Potential development tendency is forecasted based on the latest research progress.
This work elaborated the microstructure and corrosion behaviors of laser cladding (LC) FeCoCrNiAl0.5Ti0.5 high-entropy alloys (HEAs) coating on AISI 1045 steel substrate. It revealed that the LC ...FeCoCrNiAl0.5Ti0.5 HEAs coatings were composed of dendritic region (DR) and interdendritic region (IR). Furthermore, DR was mainly composed of BCC phase while IR was composed of FCC phase. There was also the transformation of BCC to L21 structure detected due to the addition of Ti element. Due to the uniform microstructure and addition of corrosion-resistant elements (such as Cr), the dual-phase HEAs coatings exhibited pretty good corrosion resistance. A dense passive film would form during the corrosion process to protect the inner structure. It was demonstrated that the corrosion rate of the coating was only 32.8% of that of the substrate. However, the pores formed during the LC process on the surface might be the initial site for pitting corrosion.
•Formation of FCC+BCC dual-phase structure observed in LC FeCoCrNiAl0.5Ti0.5 HEAs coating was investigated.•Passivation process of LC FeCoCrNiAl0.5Ti0.5 HEAs coating during electrochemical tests was illustrated.•Pitting corrosion mechanism of LC FeCoCrNiAl0.5Ti0.5 HEAs coating was studied.
W
NbMoTa refractory high-entropy alloys with four different tungsten concentrations (
= 0, 0.16, 0.33, 0.53) were fabricated by laser cladding deposition. The crystal structures of W
NbMoTa alloys ...are all a single-phase solid solution of the body-centered cubic (BCC) structure. The size of the grains and dendrites are 20 μm and 4 μm on average, due to the rapid solidification characteristics of the laser cladding deposition. These are much smaller sizes than refractory high-entropy alloys fabricated by vacuum arc melting. In terms of integrated mechanical properties, the increase of the tungsten concentration of W
NbMoTa has led to four results of the Vickers microhardness, i.e.,
= 459.2 ± 9.7, 476.0 ± 12.9, 485.3 ± 8.7, and 497.6 ± 5.6. As a result, NbMoTa alloy shows a yield strength (σ
) and compressive strain (ε
) of 530 Mpa and 8.5% at 1000 °C, leading to better results than traditional refractory alloys such as T-111, C103, and Nb-1Zr, which are commonly used in the aerospace industry.
The corrosion resistance of CrMnFeCoNi coatings with varying TiC contents and the evolution of TiC within these coatings were comprehensively investigated. These CrMnFeCoNi coatings, with different ...TiC concentrations, were fabricated using laser cladding technology. The behavior of TiC evolution in CrMnFeCoNi coatings was observed to follow a distinct pattern. At a TiC loading of 2 wt%, TiC exhibited a dispersed distribution. Interestingly, in coatings loaded with 4 wt% TiC, TiC was observed in various shapes, including elongated, square, petaled, and circular forms owing to the melting of TiC particles under the influence of a high-energy laser beam. The convection action of the molten pool combined several unmelted, partially melted, and precipitated TiC particles, resulting in diverse shapes. Furthermore, increasing the TiC content to 10 wt% led to the aggregation and fusion of TiC into clusters. Additionally, the electrochemical corrosion resistance behavior of CrMnFeCoNi coatings with varying TiC content displayed a significant correlation with the TiC concentration. As the TiC content increased, the galvanic corrosion resistance also increased. At lower TiC content levels, a higher number of electrochemical cells formed between the CrMnFeCoNi matrix and the dispersed TiC, leading to an elevated corrosion rate. In contrast, as the TiC content increased, the dispersed TiC phase fused together, reducing the likelihood of electrochemical cell formation. Notably, the electrochemical corrosion resistance of the CrMnFeCoNi coating containing 10 wt% TiC resembled that of the TiC-free coating.
•The evolution behavior of TiC in CrMnFeCoNi coatings are described.•Corrosion resistance behavior of coating shows markable relation with TiC content.•Dispersive TiC facilitates the formation of galvanic cells between TiC and substrate.
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•Ag(Cu)/nanoNi/h-BN with Nb addition wear-resistant and friction-reducing coatings prepared by laser cladding technology.•The synergistic effect of Ag(Cu)/nanoNi/h-BN with Nb in ...tribology was investigated.•Nb addition in-situ generates NbC in the composite coating and refines grain size.•Nb addition strengthens the coating and significantly improves wear resistance while keeping self-lubricating property.
Nickel-based self-lubricating composite coatings (Ni60/Ag(Cu)/nanoNi/h-BN) with different amounts of Nb were manufactured by laser cladding on the surface of 42CrMo steel. The effects of carbide forming element Nb on the microstructure evolution and tribological properties of the composite coatings were investigated. The results show that Nb is easily precipitated at grain boundaries and reacts with carbon to form the in-situ synthesized phase NbC. The grains were refined and rich substructures appeared inside, which improved the strength and hardness of the coatings. The average microhardness of the coatings with 5.5 wt% Nb addition reaches 731.5HV0.2, which is 192.1HV0.2 higher than that of NCA0(0 wt%), and 3.17 times that of the substrate. Compared to NCA0, the average friction coefficient and wear rate of NCA3 decreased by 38.1% and 30.6%, respectively. The solid lubricant formed a lubricant film during wear, and the fine grains facilitated oxidation wear, resulting in the formation of oxidation film. The lubricant film, oxidation film and the increase in hardness together improved the tribological properties of the coating.
The W and extra/in-situ TiC reinforced CoCrFeNi high-entropy alloy coating was prepared on a 45 steel substrate by laser cladding. The synergistic effect of W and ex/in-situ TiC on the microstructure ...and wear properties of the coating was studied. The results showed that the ex/in-situ TiC promoted the selection of the FCC phase with a preferred orientation to the (111) crystal plane, and the increasing of in-situ TiC and W+ex-situ TiC/in-situ TiC resulted in the transformation of the FCC phase to the BCC phase. The microstructure of W+in-situ TiC coating was more uniform and two heterogeneous nucleation points Cr3C2 and TiC appeared in the coatings during the solidification process. The wear width, depth, and volume were minimized. The wear rate (2.54×10−6 mm3/(N·m)) was an order of magnitude lower than that of CoCrFeNi (4.97×10−5 mm3/(N·m)). The W+in-situ TiC coating shows the best wear resistance. There were a small amount of wear debris and shallow furrow-like grooves, and the wear mechanism was abrasive wear. The synergistic effect of W and in-situ TiC on wear resistance was significant.
•The addition of W and in-situ TiC significantly improves the quality of the coating.•Phase compositions were predicted by Thermo-Calc software and thermodynamic calculations.•Discussion on the evolution mechanisms of microstructure and wear mechanisms.•Wear resistance explained in terms of microstructure.
•Effect of CeO2 on cracking sensitivity of the laser cladding coatings on Ti811 were studied.•The addition of CeO2 can optimize the microstructure.•Excessive CeO2 can inhibit the precipitation of the ...secondary TiC phase.•The wear properties and microhardness of laser cladding coatings with proper amounts of CeO2 are observably improved.
In this study, Ti-based composite coatings reinforced with TiC/Ti2Ni were fabricated on Ti811 titanium alloy surfaces by laser cladding TC4 + Ni60 mixed powders with different CeO2 contents (0, 1, 2, 3, and 4 wt.%). The effects of CeO2 addition on the phase composition, microstructure, microhardness, and wear properties of the coatings were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy (SEM), Vickers hardness testing, and friction wear testing. Cracks in the coatings were detected using the dye penetration method. The results showed that the coatings mainly comprised reinforced phases of TiC, Ti2Ni, TiB2, and the matrix α-Ti. Adding an appropriate amount of CeO2 could eliminate the “herringbone” cracks and improve the surface quality of the coatings. The morphology of the TiC phase changed from dendrites to particles and then to dendrites as the CeO2 content increased from 0 wt.%, 2 wt.% to 4 wt.%. CeO2 had a negligible effect on the phase compositions of the coatings but it significantly improved the microhardness and wear properties of the coatings, and the microstructure of the coating was refined by adding an appropriate amount of CeO2.
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