Assisted Laser Cladding Research Articles

Status of Research on Assisted Laser Cladding and Laser Cladding Posttreatment: A Review

Status of Research on Assisted Laser Cladding and Laser Cladding Posttreatment: A Review

Enhancing NiCrBSi coating by the spatial selectivity of in-situ shock wave assisted laser cladding

The composite energy field laser cladding (LC) can improve the mechanical properties of coatings. Based on the spatial selectivity of laser shock, in-situ shock wave assisted LC (in-situ SWALC) was proposed to fabricate NiCrBSi coatings. Firstly, based on the self-developed in-situ SWALC system, four NiCrBSi coatings were prepared on the 16Mn substrate by changing the centre-to-centre distance (CTCD) of two laser spots. Then, the differences of microstructure and element content between LC coating and in-situ SWALC coatings were analyzed. Vickers hardness tester and wear tester were used to compare the influence of CTCD. Finally, based on the theoretical calculation and propagation characteristics of the shock wave, combined with real-time monitoring of the molten pool during the in-situ SWALC process using high-speed imaging, the strengthening mechanism of the in-situ SWALC coatings was revealed. When the CTCD was 0.9 mm, the NiCrBSi coating had the highest hardness and wear properties, which was attributed to the effects of shock wave on the molten pool flow and solidification process. Therefore, the spatial selectivity of in-situ SWALC will play a important role in improving coating performance and energy efficiency, which contributes to the UN Sustainable Development Goal 9 (UN SDG 9).

Synchronous ultrasonic impact assisted laser cladding CoCrFeNiMo high entropy alloy coating: Microstructure and wear property

Synchronous ultrasonic impact treatment (UIT) is proposed to enhance the microstructure and wear property of laser cladded CoCrFeNiMo high entropy alloy (HEA) coatings on 45 steel. FCC phase with minor tetragonal σ phase and rhombic η phase are form in both conventional and UIT treated coatings. Due to the plastic deformation and high-frequency vibrations induced by UIT, dislocation interactions lead to recrystallization process at the top region coating. With the application of UIT, the columnar grains at top region of the coating transform into fine equiaxed grains owing to recrystallization. The fragmentation of dendrites occurs in the middle region of the coating, resulting in reduced dendrite arm spacing. The results also show the defects, such as pores and microcracks, are effectively eliminated within the coating. Microhardness and wear property of the coating are remarkably enhanced owing to fine-grain strengthening and second-phase strengthening. The average friction coefficient decreases from 0.56 for the conventional sample to 0.49 for the UIT treated sample, and the wear mechanism evolved from a combination of abrasive, fatigue, and oxidized wear to predominantly fatigue and oxidized wear. It indicates that synchronous ultrasonic impact assisted laser cladding is a potential method to fabricate high-performance HEA coatings.

Enhancing coating performance: Design and characterization of a Ti-Al-Si-Cr-SiC system coating using ultrasonic and rare earth assisted laser cladding

This study proposes the utilization of rare earth combined with ultrasonic-assisted laser cladding technology to address the dilution problem encountered during the laser cladding coating of Ti alloy. The aim is to improve the performance of the coating. Using Ti alloy surface as a base, a novel Ti-Al-Si-Cr-SiC multi-principal element alloy coating is fabricated. To characterize the coating, various techniques such as transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM) are employed to examine the microstructure and phase composition. The interface between the coating and the substrate is analyzed using focused ion beam and TEM. The coatings are also evaluated for corrosion and wear resistance through potentiodynamic polarization, electrochemical impedance spectroscopy, hardness, and friction tests. The results reveal that the rare earth combined with ultrasonic-assisted Ti-Al-Si-Cr-SiC coating consists of Ti4Cr phase, TiC phase, and eutectic phase (Ti3Al and Ti5Si3). The combined effect of ultrasonic energy and rare earth reduces the dilution rate of the coating, resulting in a refined coating structure that improves the wear resistance and corrosion resistance.

Effect of ultrasonic vibration-assisted laser cladding frequency on the microstructure and properties of Fe-0.5C-15Cr alloy cladding layers

In this paper, Fe-0.5C-15Cr wear and corrosion resistant alloy coating was prepared on 3Cr13 stainless steel surface by ultrasonic vibration assisted laser cladding technology. The effects of ultrasonic vibration frequency on the microstructure, microhardness and corrosion resistance of the coating were studied. The results show that the length of the dendrites of the cladding layer decreased significantly after ultrasonic vibration is applied, the grains size is refined significantly, and the morphology of the grain boundary carbides changed from fishbone-like to short rods, when the vibration frequency is 20.2 kHz, the grain refinement is the most significant, and the orientation of the dendrites is obviously weakened. The hardness of the applied ultrasonic vibration specimens increased by 10–20 HV0.2 relative to the non-ultrasonic specimens, with the increase of vibration frequency, the hardness of the cladding layer firstly increased and then slightly decreased, and the peak appeared at 20.2 kHz. The coefficient of friction of the specimens when the ultrasonic frequency of 20.2 kHz is applied is lower than that of the specimens with non-ultrasonic frequency by 12.8 %, and the abrasive wear rate is reduced by 14.3 %. After ultrasonic vibration, the pitting potential of the cladding layer increases, the dimensional passivation current density decreased, the width of the passivation zone becomes wider, and the intergranular corrosion reactivation rate decreased, When the ultrasonic frequency is 20.2 kHz and 20.4 kHz, the pitting corrosion resistance and intergranular corrosion resistance of the cladding layer are significantly improved. This is because the cavitation effect, resonance effect and acoustic flow effect of ultrasonic vibration promote the non-uniform nucleation, refine the dendrites and intergranular carbides, and promote the redistribution of the corrosion-resistant element Cr in the in-grain martensite and grain boundary carbides, increasing the content of Cr in the matrix, and thus improving the wear resistance and corrosion resistance of the cladding layer.

Effects of Pulsed Current on the Microstructure and Properties of Laser Cladded TC17 Titanium Alloy.

In this study, a titanium alloy substrate was cladded with TC17 titanium alloy powder using the pulsed-current (PC)-assisted laser cladding technique. The primary objective of this research was to assess the impact of varying pulsed current intensities on the morphology, microstructure, and properties of samples. It is observed that the utilization of pulsed currents significantly enhances the metallurgical adhesion between the samples, concurrently diminishing the occurrence of porosity within the cladding layer. The incorporation of a pulsed current also has a positive impact on the microhardness and corrosion resistance of the samples. Furthermore, the synergistic influence of laser energy and a pulsed electrical current is found to promote a structural evolution in materials towards a state with lower electrical resistance. The introduction of a pulsed current leads to preferential growth of β grains with <100>// cladding direction in the cladding zone and obtains the typical {100} < 001 > cube texture, while the substrate zone exhibits a distinctive stripe-like configuration formed by the primary α-phase constituents. The outcomes of this study show the pivotal role of pulsed currents as an auxiliary technique for enhancing the properties and effecting microstructural modifications in titanium alloys during the laser cladding process.

The microstructure and high-temperature oxidation resistance of Si-rich Mo-Si-B coatings prepared by ultrasonic vibration assisted laser cladding

Si-rich Mo-Si-B powders (Mo-62Si-5B at%) were deposited on Nb-Si based alloy by laser cladding assisted with ultrasonic vibration. The obtained coatings mainly consist of MoSi2 and (Mo, X)5Si3 (X = Nb and Ti). With the introduction of ultrasonic vibration during laser cladding, the lath-shaped MoSi2 phase transforms into cellular gradually. Meanwhile, the discrepancy on the microstructure of the top region and the bottom region is eliminated gradually, indicating that the cavitation and acoustic streaming of ultrasonic vibration not only refines the microstructure, but also homogenizes the element and phase distribution in the coatings. High-temperature oxidation experiment at 1250 ℃ were conducted to assess the oxidation resistance of the coatings. Compared with Nb-Si alloy, the coated specimens have much lower oxidation weight increase. Furthermore, with the assistance of ultrasonic vibration, the oxidation resistance of the coating is enhanced further. The oxide scales on the coatings consist of two layers: an upper amorphous aluminoborosilica with TiO2 particles dispersed and a lower crystalline SiO2 layer. With the introduction of ultrasonic vibration, the microstructure of the coatings is refined, resulting in more phase and grain boundaries in the coatings. Therefore, the diffusion of the elements to the surface is accelerated and the protective oxide scale can be formed quickly.

Novel nano-lamellar AlCoCrFeMn0.5Mo0.1Nbx eutectic high-entropy alloy coatings by ultrasonic assisted laser cladding: Microstructure and tribological behaviors

Eutectic high-entropy alloys (EHEAs) possess in-situ composite structure, which provides a novel strategy for developing wear-resistant alloys or coatings. In this work, a new-type AlCoCrFeMn0.5Mo0.1Nbx (x = 0.4 hypoeutectic, 0.65 eutectic and 0.8 hypereutectic) EHEA coatings were designed and prepared by ultrasonic assisted laser cladding. The design strategy, microstructure and tribological behaviors of the EHEA coatings were studied in detail. The Nb0.4, Nb0.65 and Nb0.8 coatings were all composed of BCC solid solution and Laves phase. The Nb0.65 coating showed typical nano-lamellar/nano-granular eutectic microstructure, while the Nb0.4 and Nb0.8 coatings had hypoeutectic and hypereutectic microstructures, respectively. The wear rates of the EHEA coatings (5.5 × 10−6 mm3/N·m for Nb0.4 coating, 5.3 × 10−6 mm3/N·m for Nb0.65 coating and 8 × 10−6 mm3/N·m for Nb0.8 coating) were significantly lower than those of most metallic and metal-ceramic composite materials. The wear mechanisms of Nb0.4, Nb0.65 and Nb0.8 coatings were slight adhesive wear and oxidation wear. Numerous regular rolling structures formed on the wear scar of Nb0.65 coating, which provides an anti-friction effect for the coating. The good carrying capacities and high hardness of the BCC, Laves and eutectic microstructures contributed to the excellent wear resistance of the EHEA coatings.

Validation of Cr6Fe18Mo in tribaloy T-800 coating fabricated by induction heating assisted laser cladding

Due to excellent performance of high-temperature wear and corrosion resistance, Tribaloy 800 (T800) alloy has been used in steel and petrochemical industry. Most scholars believe that it is Laves phase (Co3Mo2Si) that leads to high crack sensitivity of T-800 alloy. However, the formation of Laves phase is impossible under conditions where there is a tendency of phase separation. In this study, the phases composition of T-800 coatings fabricated by induction heating assisted laser cladding (IHLC) is discussed. Results show that T-800 coatings prepared by IHLC are consist of Cr6Fe18Mo5 and γ-Co supersaturated solid solution with many lattice defects. With the increase of preheating temperature, the fraction of Cr6Fe18Mo5 phase can be increased to be 51.19%, due to sufficient Fe element and maintaining time of temperature above 700 °C. The fraction of γ-Co with lattice defects and residual tensile stress in coating can be decreased with the increase of preheating temperature, which lead to a crack-free T-800 coating.

Microstructure and excellent performance enhancement of MEA base composites with multi-phase induced by ultrasonic assisted laser technology

The ceramics reinforced medium entropy alloy base composites (MEABCs) were manufactured by ultrasonic vibration (UV) assisted laser cladding (LC) process, which were investigated by scanned electron microscope (SEM), electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). The microstructure of MEABCs was mainly composed of body centered cubic (BCC), intermetallics and TiN ceramics, the fine dendrites were produced under the action of the cavitation and the acoustic flow effects of UV, increasing the dislocation density to promote the low angle grain boundary (LAGBs). The micro-hardness and the wear resistance of the composites were enhanced by the second phase and fine grain strengthening. The diffusion of the elements such as Cr/Ni and the generation of LAGBs contributed to the enhancement of the corrosion resistance of the composites.

Study on the effect of electromagnetic field on the segregation and structural property of Ni60 cladding layer

The Ni60 alloy cladding layer is prepared using electromagnetic field assisted laser cladding to investigate the effect of the variation of current magnitude and direction on its segregation and structure. The macrosegregation and the structural property of the Ni60 cladding layer are analyzed by Optical Microscopy (OM), Back Scattered Electron Imaging (BSE), Energy Disperse Spectroscopy (EDS), X-ray Diffractometry (XRD), microhardness tester, and electrochemical corrosion. The results indicate that the macrosegregation and microsegregation decrease first and then increase with rising direct current (DC) or alternating current (AC) under constant magnetic field intensity.and microhardness tends to increase and then decrease with rising current magnitude. The increasing current has a prominent effect on the bottom of the cladding layer in terms of dendrite fragmentation and structural refinement. The reduction of segregated phases such as CrB and Cr7C3 enhances the solid solution strengthening of Cr and increases the microhardness of the cladding layer. The cladding layer applied with 200 amps AC is characterized by the lowest microsegregation rate and the highest microhardness of 772 HV0.2. The specimen has a high self-corrosion potential, the lowest self-corrosion current density, and the lowest passivation current density.

A novel hybrid ultrasonic and electromagnetic field assisted laser cladding: Experimental study and synergistic effects

In this paper, a novel hybrid ultrasonic and electromagnetic (UEM) field-assisted laser cladding (LC) is proposed, and the synergistic effect between ultrasonic and electromagnetic fields in the molten pool is investigated. The experimental investigation is conducted on the impact of hybrid UEM fields on the defects (i.e. pores and cracks), surface roughness, microstructure evolution and mechanical properties of Inconel 718 coating. It is indicated that hybrid UEM fields effectively reduces the cladding layer defects and flattens the surface of the coating, promotes the columnar to equiaxed transition (CET) and produces the cellular sub-grains inside the existed grains. In addition, hybrid UEM field increases the coating microhardness and improves the wear performance of the coating. Overall, this study shows that the hybrid UEM field has the potential to manufacture practically the metallic component with high quality in the directed energy deposition field.

Microstructure and properties of Ni60 alloy coating prepared by electromagnetic compound field assisted laser cladding

In this study, Ni60 high-hardness alloy coatings were prepared on pure iron substrates by electromagnetic compound field (ECF) assisted laser cladding. By the application of synchronous alternating electric field and steady magnetic field, the effects of different electromagnetic parameters on the surface topography, phase composition and microstructure of the coatings were studied. The microhardness, electrochemical corrosion, wear property, and residual stress distributions of the coatings were also investigated. The results showed that ECF did not change the phase composition of the coatings, but had a significant influence on the microstructure. The alternating electromagnetic force generated by ECF had a mechanical stirring effect on the molten pool, which can increase the nucleation rate and play the role of refining grains. With the increase of the electromagnetic parameters, the grain refinement effect was enhanced, thus leading to a finer microstructure. Moreover, ECF can also help to reduce the cracking tendency and residual stress of the coatings. Compared with the coating prepared without ECF, the coatings with the applied ECF exhibited higher microhardness, corrosion and wear resistance, and fewer number of cracks. The coating with the best comprehensive properties can be obtained under the electromagnetic parameter of 0.2 T + 1200 A.

Microstructure of WTaNbMo refractory high entropy alloy coating fabricated by dynamic magnetic field assisted laser cladding process

WTaNbMo refractory high entropy alloy (RHEA) coatings were prepared by laser cladding assisted with reciprocating dynamic magnetic field on Inconel 718 substrates. The effects of dynamic magnetic field on the microstructure, defects and residual stress were discussed. The results show that the reciprocating magnetic field improves the microstructure homogeneity of the laser cladded WTaNbMo coating. The coatings are composed of WTaNbMo solid solution (BCC) and γ-(Ni, M). With reciprocating magnetic field assistance, the flow in the molten pool is accelerated, porosity is reduced. The residual stress inside the coating is depressed, thereby cracks in the coating are inhibited. The flow behavior in the molten pools was also discussed.

Concentration mixing and melt pool solidification behavior during the magnetic field assisted laser cladding of Fe-Cr-based alloy on 45 steel surface

Magnetic field-assisted laser cladding is an effective method in suppressing defects and improving the physical properties of the cladding layer, widely used in mold repair, aerospace, and additive manufacturing fields alike. However, magnetic field-assisted laser cladding cannot predict the effect of magnetic fields on composition mixing and melt pool solidification behavior. To solve this problem, a 3D magnetic field-assisted laser cladding numerical model including the chemical substance transfer, magnetic field, fluid flow, fluid heat transfer and dynamic grid was established in this paper. Based on the proposed model, the cladding layer geometry and concentration distributions of both the iron (Fe) and chromium (Cr) were predicted. The influences of magnetic field on the melt pool solidification behavior and the concentration mixing process were further developed. The results have shown that the maximum chromium concentration on the cladding layer marking line decreases from 10.9 wt% to 9.8 wt% within 0–0.5 T, and gradually increases to 13 wt% within 0.5–1.2 T. During the melt pool solidification, the maximum cooling rate (Gs*Rs) increases with the magnetic field strength – from 5.58 × 103 K/s to 7.1 × 103 K/s, while the morphological parameter (Gs/Rs) simultaneously decreases from 2.88 × 109 s∙K/m2 to 7.97 × 108 s∙K/m2. Such behavior implies that the crystal size decreases as the magnetic field strength increases. Additionally, the composition distribution at the beginning and bottom of the cladding layer is uneven. The crystal size decreases gradually when moving from the bottom to the top of the melt layer. Simultaneously, the crystal structure changed from slatted crystals at the bottom to columnar, cellular, and equiaxed crystals at the top. As such, the study provides an effective way to predict elemental concentrations and solidification behavior during magnetic field-assisted laser cladding.

Effect of Electromagnetic Field on Wear Resistance of Fe901/Al2O3 Metal Matrix Composite Coating Prepared by Laser Cladding.

Fe901/Al2O3 metal matrix composite (MMC) coatings were deposited on the surface of 45 steel via electromagnetic field (EF)-assisted laser cladding technology. The influences of EF on the microstructure, phase composition, microhardness, and wear resistance of the Fe901/Al2O3 MMC coating were investigated. The generated Lorentz force (FL) and Joule heating due to the application of EF had a positive effect on wear resistance. The results showed that FL broke up the columnar dendrites. Joule heating produced more nuclei, resulting in the formation of fine columnar dendrites, equiaxed dendrites, and cells. The EF affected the content of hard phase in the coatings while it did not change the phase composition of the coating, because the coatings with and without EF assistance contained (Fe, Cr), (Fe, Cr)7C3, Fe3Al, and (Al, Fe)4Cr phases. The microhardness under 20 mT increased by 84.5 HV0.2 compared to the coating without EF due to the refinement of grains and the increased content of hard phase. Additionally, the main wear mechanism switched from adhesive wear to abrasive wear.

Effect of steady magnetic field on microstructure and properties of laser cladding Ni-based alloy coating

In this paper, Ni-based alloy coating was prepared on pure iron substrate by steady magnetic field assisted laser cladding technology. The influence mechanism of steady magnetic field on the Ni-based coating was investigated by analyzing the macro-morphology, phase composition, microstructure, element composition and properties of the coatings, respectively. The results reveal that external magnetic field can restrain the surface fluctuation of the coatings. It has no effect on the phase composition of the coatings. Compared with the coating prepared without magnetic field assistance, the grains of the coatings prepared under the magnetic induction intensities of 0.1 T, 0.15 T and 0.2 T are all refined. The solid solubility of the γ-Ni matrix is also increased. Hard phases CrB in the microstructures appear clustered aggregation and preferential orientation with the increase of the magnetic induction intensity. The application of steady magnetic field is beneficial to reduce the number of cracks on the surface and improve the microhardness of the coatings. The coating exhibits the best comprehensive property under the magnetic induction intensity of 0.2 T. Under the action of steady magnetic field, the electromagnetic braking effect and the thermoelectric magnetic fluid effect can both influence the laser cladding process. The surface morphology of the coating is mainly affected by the electromagnetic braking effect. The solidification microstructure is mainly controlled by the thermoelectric magnetic fluid effect.

Research on Dilution of Laser Cladding Assisted by Pulsed Current Based on Orthogonal Experiment

With characteristics of high cladding efficiency, small grain size and low porosity, follow-up feeding pulse current assisted laser cladding can realize online self-healing of cracks on the cladding layer and get a crack-free cladding layer. It is a very promising new laser cladding technology. In this study, effects of cladding parameters (laser power, scanning speed, powder feed rate, pulse current, pulse frequency and pulse width) on dilution rate of coating were discussed through a six-factor three-level orthogonal experimental design method. Results demonstrated that laser power, scanning speed and powder feed rate can influence dilution ratio greatly, while pulse current, pulse frequency and pulse width influence the dilution ratio slightly. Among the top three major factors, laser power can influence the dilution ratio mostly, followed by powder feed rate and scanning speed. The dilution ratio increases with the increase of laser power, scanning speed and pulse width, but it decreases with the increase of powder feed rate and pulse frequency. With the increase of pulse current, the dilution ratio decreases firstly and then increases.

A study on the influence mechanism and optimization of physical field parameters of electromagnetic-ultrasonic compound field–assisted laser cladding technology

A study on the influence mechanism and optimization of physical field parameters of electromagnetic-ultrasonic compound field–assisted laser cladding technology

Effect of magnetic field waveform on microstructure and properties of laser cladding

Ni60 coating-45 steel substrate was prepared by magnetic field assisted laser cladding with four waveforms:steady magnetic field (SMF), alternating magnetic field (AMF), pulsed magnetic field (PMF). The effects of four kinds of magnetic fields on the morphology, microstructure, phase composition and microhardness of the coating were studied, and the magnetic field mechanism on the coating was briefly analyzed. Results revealed that the addition of magnetic field can significantly reduce the number of cracks, facilitate grain refinement and improve the coating hardness. The improvement degree of four kinds of magnetic fields on the coating performance is: PMF > APMF > AMF > SMF. Among them, the coating performance is prominently improved by PMF, but there is a serious segregation of hard phase; The segregation of hard phase and the slender of the structure occur in the APMF.