Wide-Band Laser Cladding Research Articles

Design and Numerical Analysis of an Inside-Beam Powder Feeding Nozzle for Wide-Band Laser Cladding.

Wide-band laser cladding technology has emerged as a solution to the limitations of traditional cladding techniques, which are small single-path dimensions and low processing efficiency. The existing wide-band cladding technology presents challenges related to the high precision required for the laser-powder coupling and the significant powder-divergence phenomenon. Based on the inside-beam powder-feeding technology, a wide-band powder-feeding nozzle was designed using the multi-channel powder flow shaping method. The size of the powder spot obtained at the processing location can reach 40 mm × 3 mm. A computational fluid dynamics analysis using the FLUENT software was conducted to investigate the impact of the nozzle's structural parameters on the powder distribution. It was determined that the optimal configuration was achieved when the powder-feeding channel was 8, and the transverse and longitudinal dimensions for the collimating gas outlet were 0.5 mm and 1 mm, respectively. Among the process parameters, an increase in the carrier gas flow rate was found to effectively enhance the stability of powder transportation. However, the powder feed rate had minimal impact on the powder concentration distribution, and the collimating gas flow rate appeared to have a minimal effect on the divergence angle of the powder stream. Wide-band laser cladding experiments were conducted using the designed powder-feeding nozzle, and a single-path cladding with a width of 39.96 mm was finally obtained.

Modeling of melt pool and thermal field simulation for wide-band laser cladding

Modeling of melt pool and thermal field simulation for wide-band laser cladding

Prediction of the bead profile for wide-band laser cladding via hybrid model of mathematics and thermal simulation

Wide-band laser cladding has high deposition rate and low dilution due to the large laser spot and rectangular powder nozzle. A mathematical model was proposed to predict the track cross-section profile for wide-band laser cladding. The melt pool morphology and powder spatial concentration were taken into consideration to improve the accuracy of the model. Thermal field simulation was carried out to study the melt pool evaluation with process parameters, while infrared images were used to verify the simulation fidelity. Powder stream photographs were taken via a CCD (charge coupled device) camera to obtain the powder spot size. Single and multi-track cladding experiments were conducted, and calculated contours of the model coincide well with the experimental results. Simulated and measured melt pool width and length agree with in 2.16% and 2.36% of error, respectively. The error of predicted cross section area is less than 9.35%. The model also has good ability to predict the powder efficiency and morphology of the cladding layer.

Numerical simulation study on the formation mechanism of hydroxyapatite-silver gradient bioactive ceramic coatings under wide-band laser cladding

Numerical simulation study on the formation mechanism of hydroxyapatite-silver gradient bioactive ceramic coatings under wide-band laser cladding

Study on Mechanical Properties of AlFeCrMoNi1.8Nb1.5 Eutectic High-Entropy Alloy Coating Prepared by Wide-Band Laser Cladding

In this study, AlFeCrMoNi1.8Nb1.5 (at.%) eutectic high-entropy alloy (EHEA) coating was successfully prepared on the surface of M2 high-speed steel (HSS) by wide-laser cladding. The effects of laser defocusing amount, laser power, scanning speed, and preset powder thickness on the formation quality of the EHEA coating were studied by the orthogonal experimental design, then the mechanical properties of the coating prepared by water-cooled solidification under optimal process parameters were studied. The experimental results showed that the optimal laser cladding process parameters are defocusing with an amount of −30 mm, laser power of 4 kW, scanning speed of 3 mm/s, and preset powder thickness of 1.5 mm. The substrate exhibited a favorable metallurgical bond with the coating, characterized by a stable interface devoid of any holes or cracks. Furthermore, the coating, which was prepared using water cooling, displayed a finer lamellar eutectic structure comprising FCC and Laves phases. The microhardness of the coating (544 HV0.2) was significantly higher than that of the substrate M2 HSS (~220 HV0.2), accompanied by good wear resistance.

The effects of graphene oxide doping on the friction and wear properties of TiN bioinert ceramic coatings prepared using wide-band laser cladding

In this study, aiming to improve the tribological properties of TiN ceramic coatings, the effects of different pairs of sliding balls on the coatings during wear were investigated, which guided the application of the TiN coatings. Using the wide-band laser cladding technique, TiN bioinert ceramic coatings doped with graphene oxide (GO) nanosheets as self-lubricating phases were prepared on Ti6Al4V. The GO doping did not change the main phase compositions of the coating and made an improvement in the coating quality. GO doping significantly affected the wear resistance of the coating and effectively reduced its friction coefficient. When the coating was sliding against Si3N4, GO doping slightly reduced the wear resistance of the coating; while the coating was sliding against Ti6Al4V alloy and ultrahigh molecular weight polyethylene (UHMWPE), respectively, GO doping significantly improved the wear resistance of the coating. When the doping amount of GO was 3 wt%, the friction coefficients of the coating during sliding against the three material kinds decreased the most: 22 %, 17 %, and 25 % for the Si3N4, Ti6Al4V, and UHMWPE, respectively. Both oxidation wear and abrasive wear were observed when the GO-doped TiN self-lubricating ceramic coatings sliding against Si3N4 balls, Ti6Al4V balls and UHMWPE balls, and fatigue wear was also observed when the coating sliding against Si3N4 balls. The primary antifriction mechanism of the GO-doped TiN ceramic coating during sliding against Si3N4 balls was that the GO in the coating was exposed to the sliding surface to form a lubricating film. It is feasible to apply GO-doped TiN bioinert ceramic coating to artificial joint.

In-situ reinforced phase evolution and wear resistance of nickel-based composite coatings fabricated by wide-band laser cladding with Nb addition

In this paper, Ni60/WC composite coatings were prepared by wide-band laser cladding technique. The effects of the addition of the strong carbide forming element Nb on the microstructure and properties of the composite coatings were studied by microstructure characterization, phase identification, microhardness, wear resistance, and other properties. The results show that the in-situ synthesized phases in the laser molten pool are mainly composed of γ-Ni solid solution and strengthening phases such as Cr7C3, Cr23C6, Cr5B3, and NbC. With the increase of Nb content in the composite cladding layer, the formation of Cr7C3 is inhibited, the amount of residual WC decreases, while the content of NbC increases, and the morphology of the precipitated phase containing NbC changes from coarse strips to fine needle-like agglomerates and then to blocky. Among them, when the Nb content reaches 3 wt%, the needle-like agglomerated NbC is uniformly distributed and has good adhesion to the substrate, which can effectively reduce the breakage and shedding of the hard phase during the wear process and has the best wear resistance performance. Overall, the alloying effect of Nb changed the composition and morphology of the strengthening phase in the cladding layer of the nickel-based composites, reducing the hardness of the cladding layer but enhancing the microstructure uniformity, resulting in improved wear resistance of the coating.

Study on the In-Situ Reinforced Phase Evolution and Wear Resistance of Nickel Based Ceramic Composite Coating by Nb Alloying in Wideband Laser Cladding

Study on the In-Situ Reinforced Phase Evolution and Wear Resistance of Nickel Based Ceramic Composite Coating by Nb Alloying in Wideband Laser Cladding

Laser cladding preparation of HA-Ag gradient bioactive ceramic coating: A feasibility study

Laser cladding is one of the most potential techniques to prepare hydroxyapatite (HA) bioactive ceramic coating on titanium (Ti) surface to enhance bioactivity of orthopedic implants. However, there exists a disadvantage that HA is easy to be decomposed due to laser overheating for melting Ti metal or converted into a non-bioactive substance due to chemical reaction with Ti metal. In this paper, a novel technique for preparing a higher bioactive ceramic coating with a three-layer gradient structure on medical Ti substrate surface by wide-band laser cladding process was proposed. Firstly, a silver (Ag) barrier layer was prepared on Ti substrate by using 100 wt% Ag powder, which was used to block the diffusion of Ti element to the coating, so as to avoid the chemical reaction between HA and Ti to generate non-bioactive calcium titanate (CaTiO 3 ). Secondly, a transition layer was prepared in the middle by using the powder mixture of HA and Ag in weight ratio of 3:1 as the cladding material on the barrier layer. Finally, a HA bioactive ceramic layer was prepared on the transition layer at lower laser power density by using 100 wt% HA powder, which could help to create osseointegration between the coating and the host bone tissue. The morphology, phase compositions of the three functional layers of the HA-Ag bioactive ceramic coating were investigated, and their formation mechanisms were analyzed. The bioactivity and biocompatibility of the coating were assessed respectively by simulated body fluid (SBF) immersion test and cell culture test in vitro . The results showed that the main phase of the bioactive layer of the gradient coating was HA, which exhibited excellent bioactivity and biocompatibility. The proposed method of bioactivity modification for Ti metal implant surface is feasible, which has a good prospect for bone tissue engineering applications. • A bioactive ceramic coating with three-layer gradient structure was prepared. • The Ag barrier layer prevented Ti element in substrate from diffusing to coating. • The coating had excellent bioactivity and potential ability of osseointegration. • The coating exhibited comparable biocompatibility to medical Ti metal.

Numerical Simulation of the Temperature and Stress Fields in Fe-Based Alloy Coatings Produced by Wide-Band Laser Cladding

Numerical Simulation of the Temperature and Stress Fields in Fe-Based Alloy Coatings Produced by Wide-Band Laser Cladding

The alloying effects of Cr on in-situ phase evolution and wear resistance of nickel composite coatings fabricated by wide-band laser deposition

In this work, nickel based composite coatings reinforced with WC and Cr particles were deposited by wide-band laser cladding. The alloying effects of Cr were investigated by microstructure characterization, phased identification, and property analysis such as microhardness and wear resistance. Results indicated the in-situ synthesized phases in laser pool mainly composed of γ-Ni solid solution, (Cr,W)5B3, (Cr,W)7C3 and Cr23C6. Large quantity of block (Cr,W)5B3 phases were synthesized as the Cr addition was blow 4 wt%. However, the coarse strip (Cr,W)7C3 phase became the dominate precipitates as the Cr addition further increased. Statistics analysis of particle morphology showed that the (Cr,W)5B3 phase was uniformly distributed block shape with median particle diameter D50 = 8.97 μm, while the (Cr,W)7C3 phase was coarse strip shape with median diameter D50 = 12.77 μm. The average microhardness and wear resistance showed the best in coating 2# with 4 wt% Cr addition (873±85HV and 1.8 × 10−6 g/m respectively). Worn surfaces indicated the strip (Cr,W)7C3 phases easily peeled off and thus decreased the wear resistance of composite coatings. The results in this work showed that the constitution and content of reinforced in-situ phases in nickel composite coatings could be modified by the alloying effects of Cr. As a result, the hardness and wear resistance were also improved with optimized Cr addition.

Uniformly Dispersed Carbide Reinforcements in the Medium-Entropy High-Speed Steel Coatings by Wide-Band Laser Cladding

A medium-entropy high-speed steel (ME-HSS) coating with the 76 at.% of Fe and multiple alloying elements was prepared by the wide-band laser cladding. Compared with the commercial W6Mo5Cr4V2 (M2) HSS coating which contains a large number of network lamellar M2C-type carbides along the grain boundaries, the presented ME-HSS coating has a high quantity of finer and more uniformly dispersed MC-type carbides; on the other hand, the coating has less retained austenite and much lower brittleness as well as similar secondary hardening effect and tempering hardness.

Effects of Ti addition on microstructure homogenization and wear resistance of wide-band laser clad Ni60/WC composite coatings

Ni60/WC composite coatings were fabricated by wide-band laser cladding. The effects of Ti addition on microstructure homogenization and coating properties were investigated. Coating microstructure, phase constitution, microhardness and wear resistance were studied and grading analysis of in-situ synthesized ceramic particles was carried out. Results indicated that ceramics particles of Cr5B3 and M23C6 (M represents for Cr and W) carbides were in-situ synthesized in original Ni60-20WC coatings. With Ti addition, dissolution of original WC was facilitated and lots of TiC particles were synthesized instead of M23C6 carbides. Furthermore, the block Cr5B3 particles were greatly homogenized due to the net structure formed by dispersive TiC particles. With Ti addition, D50 of particle size decreased from 8.94μm to 4.45μm and particle morphologies were transformed from star-like shapes to uniform square blocks. Microhardness distribution became more uniform with average value decreased from 799±89HV0.2 to 744±77HV0.2. Due to the homogenized ceramic particles, wear resistance of coatings with Ti addition was enhanced to 2.6 times that of the original coatings.

Microstructure evolution and growth control of ceramic particles in wide-band laser clad Ni60/WC composite coatings

Nickel based composite coatings reinforced with WC particles were fabricated on substrate of Q550 steel utilizing wide-band laser cladding technology. To control the microstructure evolution and growth behavior of ceramic particles, different laser power was applied in manufacturing process. The microstructure characteristics were examined by optical microscope (OM) and field emission scanning electron microscopy (FE-SEM). X-ray diffraction (XRD) was applied to analyze the phase constitution of composite coatings. The wear resistance was examined by dry sliding tests utilizing MM2000 abrasion testing machine. The results showed that the added WC particles was partly dissolved and reacted with the molten Ni60 powders. Special cored-eutectic structure was formed at the top region of coatings, consisting of the inner boride ceramic and the fine lamellar eutectic around. Combining the XRD results with EDS analysis, the ceramic were confirmed as W2B5 and the eutectics were a mixture of (Cr, W)23C6 and γ-Ni(Fe). Adjustment of wide-band laser power had great influence on the growth behavior of the cored-eutectic structure. Due to the greatly refined ceramic-eutectic structure, composite coatings with laser power P=3.6kW exhibited excellent wear resistance which was about 6.8 times that of substrate steel.

Investigation on cored-eutectic structure in Ni60/WC composite coatings fabricated by wide-band laser cladding

Ni60 composite coatings reinforced with WC particles were fabricated on the surface of Q550 steel using LDF4000-100 fiber laser device. The wide-band laser and circular beam laser used in laser cladding were obtained by optical lens. Microstructure, elemental distribution, phase constitution and wear properties of different composite coatings were investigated. The results showed that WC particles were partly dissolved under the effect of wide-band fiber laser irradiation. A special cored-eutectic structure was synthesized due to dissolution of WC particles. According to EDS and XRD results, the inside cores were confirmed as carbides of M23C6 enriched in Cr, W and Fe. These complex carbides were primarily separated out in the molten metal when solidification started. Eutectic structure composed of M23C6 carbides and γ-Ni(Fe) grew around carbides when cooling. Element content of Cr and W is lower at the bottom of cladding layer. In consequence, the eutectic structure formed in this region did not have inside carbides. The coatings made by circular laser beam were composed of dendritic matrix and interdendritic eutectic carbides, lacking of block carbides. Compared to coatings made by circular laser spot, the cored-eutectic structure formed in wide-band coatings had advantages of well-distribution and tight binding with matrix. The uniform power density and energy distribution and the weak liquid convection in molten pool lead to the unique microstructure evolution in composite coatings made by wide-band laser. Experiment results indicated the wear resistance and microhardness of composite coatings were both significantly improved.

人成骨细胞在宽带激光熔覆Nd2O3活性涂层表面的成骨性能

人成骨细胞在宽带激光熔覆Nd₂O₃活性涂层表面的成骨性能

Effect of Mixed Multiple Rare Earth Oxide on the Microstructure of Bioceramic Coating Prepared by Wide Band Laser Cladding

In order to researching the microstructure of bioceramic coating on the surface medical titanium alloy (Ti–6Al–4V), the gradient bioceramic coatings are fabricated by wide-band laser cladding. The influence of multiple rare earths oxide La2O3 and CeO2 on microstructure of bioceramic coating were studied. The experimental results demonstrated that mixed La2O3 and CeO2 have an effect on forming-ability of HA\β-TCP in bioceramic coating and also refined the grain of bioceramic coatings. The largest amount of HA\β-TCP is presented among all the groups when the contents of La2O3 and CeO2 are 0.6wt.%, 0.4 wt.%, respectively.

The Bioactivity of Gradient Composite Bioceramic Coating with Two Kinds of Rare Earth Oxide Fabricated by Wide Band Laser Cladding

To improve bioactivity of gradient bioceramic coating, the coating with two kinds of rare earth oxide was produced by wide band laser cladding technique. As the experimental results, whichadded0.6wt.% La2O3 fixedly, and increased the addition amount of the CeO2, when the addition of CeO2fulfill 0.4wt.%, the amount of HA-β-TCP is the largest in this experiment. Soaking the specimens in SBF for 14 days, the coating blended 0.6wt% La2O3 and 0.4wt% CeO2, then a great quantity of Ca-P white particles can be found on coating, which confirmation this bioceramic coating is of best bioactivity.

The Microstructure of Gradient Composite Bioceramic Coating with Single and Multiple Rare Earth Oxide Fabricated by Wide Band Laser Cladding

To improve bonding strength between Ti alloy and bioceramic coating and to eliminate thermal stress during laser cladding, gradient bioceramic coating materials is designed. The bioceramic coating is fabricated by wide band laser cladding technique. And the effect of adding single and multiple rare earth oxide on microstructure is investigated. The samples are soaked with SBF for 14 days, the experimental results indicate that when the content of single rare earth oxide is 0.6wt.%Y2O3, a large number of bioactivity phase and chrysanthemum shape microstructure can be observed. When the content of single rare earth oxide is 0.2wt.%Sm2O3, a lot of bioactivity phase and coral reef shape microstructure can be observed. When the content of multiple rare earth oxide is 0.3wt.%Sm2O3 and 0.4wt.%Y2O3, a large amount of bioactivity phase and more homogeneous and dense spherical particles can be observed on coating, which demonstrates the microstructure is of better bioactivity.

The Bioactivity of Gradient Composite Bioceramic Coating with Different Contents of Multiple Rare Earth Deoxide Fabricated by Wide Band Laser Cladding

To improve bonding strength between titanium alloy and coating and to eliminate thermal stress during laser cladding, a gradient coating materials is designed. And the gradient coating with different contents of multiple rare earth deoxide was produced by wide band laser cladding technique. The experimental results indicate that when addition of Sm2O3 is fixed to 0.3wt.%, as addition of Y2O3 increases, the microstructure of bioceramic is different. When addition of Y2O3 reaches 0.4wt.%, the amount of Ca-P based bioactive phases such as HA, α-TCP as well as β-TCP becomes biggest. After soaking the coating with 0.3wt.% Sm2O3 and 0.4wt.% Y2O3 in SBF for 14 days, a large amount of Ca-P white spherical particles can be observed on coating, which demonstrates the bioceramic coating is of best bioactivity.