Laser Surface Cladding Technique Research Articles

Effect of SiC addition on laser-based CoNi binary alloy coatings on Ti-6Al-4V alloy

AbstractThis research explores the impact of variations in laser scanning speed and the incorporation levels of SiC-Ni-Co powders on Ti-6Al-4V alloy using laser surface cladding technique. Key parameters, including a consistent laser power of 700 W, a 4 mm beam spot size, a powder feed rate of 1.0 g/min, and a gas flow rate of 3 L/min, along with fixed powder compositions, were maintained. The laser scanning speeds were adjusted to 0.4 m/min, 0.8 m/min, and 1.2 m/min. Microstructural analyses were carried out using scanning electron microscopy (SEM) while Vickers microhardness was employed to assess coating hardness, and corrosion properties were evaluated using a linear potentiodynamic polarization technique. Following the corrosion attack, the protective oxides formed were identified through SEM and X-ray diffractometer (XRD). The results revealed a strong metallurgical relationship between the clad layer and the substrate, demonstrating the effectiveness of the laser-clad technique. Particularly, the highest laser scan speed exhibited the most significant improvements in hardness and corrosion resistance. The coatings displayed an average hardness value of 1269.20 HV0.1, a notable fourfold increase compared to the substrate's value of 334 HV0.1. Concerning corrosion, a clear correlation emerged between scan speed and polarization resistance, confirming that higher scan speeds could lead to enhanced polarization resistance.

Microstructural and tribological behavior of in situ synthesized Ti/Co coatings on Ti-6Al-4V alloy using laser surface cladding technique

The enhancement of the tribological properties of titanium (Ti-6Al-4V) has been the subject of wide range research over the years. The constraints associated with Ti-6Al-4V in severe tribological conditions due of its low hardness and poor wear properties can be enhanced by appropriate enhancement of the microstructure via surface modification technique without altering the bulk material. In this work, Cp-Ti and Co powders were deposited at different admixed percentages by laser cladding on Ti-6Al-4V substrates with respect to laser processing parameters. The laser optimized parameters used are laser power 900 W, powder feed rate 1.0 g/min, beam spot size 3 mm, and gas flow rate 1.2 L/min while scan speed were varied at 0.6and 1.2m/min. The microstructural evolution as well as wear morphology of the coatings were studied using scanning electron microscope equipped with energy dispersed spectrometry (SEM/EDS) while the phase identification were observed using X-ray diffractometer (XRD). Microhardness values of the coatings were obtained while wear test was conducted using a reciprocating set up. The coatings exhibited a good metallurgical bonding between the coatings and the substrate. Results revealed that laser clad sample with high scan speed was more effective in improving the hardness and wear resistance of Ti-Co/Ti6Al4Vcompared to low scan speed. The coatings possess an average hardness value of 730 HV0.1, a value that is about two times greater than that of the substrate. The enhanced wear resistance with high laser scan speed has been attributed to the presence of flower-like structures and formation of fractions of CoTi2, CoTi, AlTi2, AlCo5, AlCo2Ti, and Al2Ti inter-metallic phases dispersed within the coating matrix. In addition, analysis of worn surfaces and wear mechanism indicated improved resistance to tribological actions.

A study on the influence of laser power on microstructural evolution and tribological functionality of metallic coatings deposited on Ti-6Al-4V alloy

Metallic Ti–Co binary coatings were fabricated on titanium alloy (Ti–6Al–4V) substrate by laser surface cladding technique using a continuous wave RofinSinar 4 kW Nd: YAG laser. The influence of laser power on microstructure, hardness and tribological performance of Ti–Co laser clad coatings on titanium alloy (Ti–6Al–4V) was examined. Laser powers of 750 and 900 W were varied with constant scan speed of 1.2 m/min. A beam size of 3 mm and argon shield gas flow rate of 1.2 L/min were set as the operating laser parameters. Phase identification and morphological studies of the coatings were carried out using X-ray diffractometry (XRD) and scanning electron microscopy (SEM), respectively. Based on the results of laser process optimisation, it was observed that both laser powers produced clad coatings with good metallurgical bond with no cracks or pores in the coatings. With respect to the substrate (Ti–6Al–4V), the microstructure, hardness and friction/wear behaviour of Ti–Co coatings on Ti–6Al–4V substrate were enhanced obviously.

The Effect of Laser Based Synthesized Ti-Co Coating on Microstructure and Mechanical Properties of Ti6al4v Alloy

The distinctive properties of Ti-6Al-4V alloy coupled with its poor tribological properties make it a subject of numerous researches. While titanium alloys possesses vast applications and excellent properties, their low hardness and poor tribological behaviour have retarded their applications in engineering applications. In this work, the microstructures and micro - hardness values of Ti-Co intermetallics reinforced on Ti6Al4V, were investigated. Laser surface cladding technique was employed using Nd: YAG high power laser beam for the synthesis of the powders. The feedstock powders were premixed and deposited on Ti6Al4V with varying compositions at scan velocity of 1.2 m/min. Laser power of 900W and beam size of 3mm with argon shield gas flow rate of 1.2l/min were set as the operating laser parameters. Phase identification and morphological studies of the resultant coatings were carried out using scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS) respectively. The coatings displayed fine microstructure and good metallurgical bonding with the substrate containing minute or no defects such as cracks and pores. The results revealed the formation of fractions of Ti2Co and TiCo3 inter - metallic phases dispersed within the coating matrix which could be responsible for the enhanced properties attained. The hardness was increased by 150% as against the substrate.

Downscaling of conventional laser cladding technique to microengineering

To get an adequate response to the high increase of micro-products demand, new techniques have been developed by different types of industries in the last years. One approach is to adapt the laser surface cladding technique to the scale of microengineering. A new experimental configuration has been developed based on a highly stable high power laser with a high beam quality and a micro-feeder adequate to supply submicron particles. This work collects our efforts to extend the operation range of the laser cladding to the laser micro-cladding in order to produce micro-coatings. The viability of this new technique has been demonstrated by depositing coatings with geometrical characteristics in the micrometer range (minimum values obtained: 32 μm of width and 12 μm of height).

Studies on compositionally graded silicon carbide dispersed composite surface on mild steel developed by laser surface cladding

In the present study, an attempt has been made to develop a compositionally graded SiC dispersed phase on the surface of mild steel substrate by two steps laser surface cladding technique, with a top layer having 85% Fe + 15% SiC and bottom layer of 95% Fe + 5% SiC. Laser surface cladding was conducted using a continuous wave CO 2 laser, and simultaneous feeding of a mixture of Fe and SiC (in the above mentioned ratio) with Ar as shrouding atmosphere. The microstructure of the composite layer consisted of dispersion of SiC particles in the matrix of ferrite and iron silicide (Fe 2Si). In the clad layer, SiC particles were found to be partially dissociated and the degree of dissociation was higher at the bottom layer as compared to the top layer. Area fraction of particles was found to be maximum at the surface and decreased with depth. The microhardness of the surface was improved to a maximum of 600 VHN (at the surface) as compared to 190 VHN of mild steel substrate and decreased gradually with depth. A significant improvement in wear and corrosion resistance on the clad surface was observed.

Structure of laser cladded tungsten carbide composite coatings

Carbide-metal matrix composite materials are used in applications were high wear resistance is critical. The laser surface cladding technique offers new advantages in depositing composite materials wear resistant coatings. Layers of WC in Co and Ni-based alloys matrix composites have been laser cladded on a low carbon steel substrate. Due to the right selection of the laser processing parameters during laser surface cladding porosity and crack free WC-metal composite coatings have been produced. The results of optical and SEM microstructure observations, X-ray phase, and EDS chemical composition analysis as well as cross-sectional microhardness distribution have been presented. The longer the laser beam–composite material interaction time, the higher level of the dissolution of primary carbide phase in metal matrix is to be expected. The primary WC particles dissolution degree depends also on their mesh size and volume fraction in composite material. The processing conditions should be optimized to keep the primary carbides dissolution at minimum.

Microstructural characterisation of laser clad coating of nickel based alloy with dissolved SiCp

A laser surface cladding technique was used to form an Ni–Cr–B–Si–C alloy coating doped with 30 vol.-%SiCp on an AISI 1045 steel substrate. The SiC particles completely dissolved during the melting stage of cladding. The bonding zone has a microstructure of a γ-Fe band resulting from epitaxial planar growth followed by a cellular dendritic eutectic of γ-Ni + M23 (C,B)6 on solidification, characterised by directional solidification. The microstructure of the cladding layer is composed of very closely spaced net-like M23 (C,B)6 primary dendrites and a small amount of interdendritic γ-Ni + M3 (B,Si) lamellar eutectic, and has primary small spherical graphite particles in the upper part of the cladding layer. The rapid solidification involved in the laser cladding resulted in substantial extension of solid solubility of Si in the γ-Ni terminal solid solution. The M23 (C,B)6 primary dendrites contain a high density of stacking faults. The eutectic M3 (B,Si) phase exhibits a periodic structure.

The corrosion behaviour of stainless steel cladding applied by laser

Summary The properties of a stainless steel coating produced on a carbon steel using the high‐power laser surface cladding technique were studied. The cladding was obtained by injecting type 316 stainless steel powder. The composition and properties of the new coating were similar to those of a stainless steel of the same type obtained by conventional methods.

Microstructure and wear properties of laser clad Fe−Cr−Mn−C alloys

The laser surface cladding technique was used to formin situ Fe-Cr-Mn-C alloys on AISI 1016 steel substrate. In this process mixed powders containing Cr, Mn, and C with a ratio of 10∶1∶1 were delivered using a screw feed, gravity flow carrier gas aided system into the melt pool generated by a 10 kw CO2 laser. This technique produced ultrafine microstructure in the clad alloy. The microstructure of the laser surface clad region was investigated by optical, scanning, and transmission electron microscopy and X-ray microanalysis techniques. Microstructural study showed a high degree of grain refinement and an increase in solid solubility of alloying elements which, in turn, produced a fine distribution of complex types of carbide precipitates in the ferrite matrix because of the high cooling rate. An alloy of this composition does not show any martensitic or retained austenite phase. In preliminary wear studies the laser clad Fe-Cr-Mn-C alloys exhibited far superior wear properties compared to Stellite 6 during block-on-cylinder tests. The improved wear resistance is attributed to the fine distribution of metastable M6C carbides.

Evolution of microstructure in laser clad Fe–Cr–Mn–C alloy

Abstract The laser surface cladding technique was used to form in situ Fe–Cr–Mn–C alloys on AISI 1016 steel substrate. In this process, mixed powders containing Cr, Mn, and C in the weight ratio 10: 1 : 1 were delivered using a screw feed, gravity flow, carrier gas aided system into the melt pool generated by a 10 kW CO2 laser. This technique produced an ultrafine microstructure in the clad alloy layer. The microstructure of the laser surface clad region was investigated by optical, scanning and transmission electron microscopy, and X-ray microanalysis techniques. Microstructural study showed a high degree of grain refinement and an increase in solid solubility of alloying elements which, in turn, produced a fine distribution of complex types of carbide precipitates in the ferrite matrix because of the high cooling rate. An alloy of this composition does not show any martensitic transformation or retained austenite phase.MST/356