Effect of CeO₂ on Microstructure and Wear Resistance of TiC Bioinert Coatings on Ti6Al4V Alloy by Laser Cladding

Optimizing laser cladding powder injection parameters to shape bioactive glass nano-coated zirconium oxide for biomedical application

Human body is highly sensitive and repairing often incurs pain and expenses. Strength of the materials degraded by poor joint (either weld or link). New material technology is proposed many biomaterials for repairing bone and tissue and also many bio-implantation applications. Especially bioactive material like bioactive glass is used for biomedical applications for replacement and repairing organs in human body. This research work focuses on suggesting material of S53P4 bioactive glass Nano-coated Zirconium dioxide for manufacturing artificial knee implant for fixing in human body. The substrate of Zirconium dioxide is Nano-coated with S53P4 bioactive glass by means of laser cladding process. The laser cladding process parameters were optimized by Taguchi method to enhance mechanical properties like compressive strength, wear resistance and microhardness of Zirconium dioxide implant material. The key parameters like Laser Power (1 kW, 2 kW, 3 kW and 4 kW), beam diameter (2 mm, 3 mm, 4 mm and 5 mm), powder feed rate (10 g/min, 15 g/min, 20 g/min and 25 g/min) and scanning speed (3 mm/s, 4 mm/s, 5 mm/s and 6 mm/s) were considered. The optimal parameters result the higher compressive strength and microhardness are obtained as 373 MPa and 898.37 HV0.2 and minimum wear volume is attained as 0.148 mm3 in the Nano-coated implant material.

Research Progress of Laser Cladding on the Surface of Titanium and Its Alloys

Titanium (Ti) and its alloys have been widely employed in aeronautical, petrochemical, and medical fields owing to their fascinating advantages in terms of their mechanical properties, corrosion resistance, biocompatibility, and so on. However, Ti and its alloys face many challenges, if they work in severe or more complex environments. The surface is always the origin of failure for Ti and its alloys in workpieces, which influences performance degradation and service life. To improve the properties and function, surface modification becomes the common process for Ti and its alloys. The present article reviews the technology and development of laser cladding on Ti and its alloys, according to the cladding technology, cladding materials, and coating function. Generally, the laser cladding parameters and auxiliary technology could influence the temperature distribution and elements diffusion in the molten pool, which basically determines the microstructure and properties. The matrix and reinforced phases play an important role in laser cladding coating, which can increase the hardness, strength, wear resistance, oxidation resistance, corrosion resistance, biocompatibility, and so on. However, the excessive addition of reinforced phases or particles can deteriorate the ductility, and thus the balance between functional properties and basic properties should be considered during the design of the chemical composition of laser cladding coatings. In addition, the interface including the phase interface, layer interface, and substrate interface plays an important role in microstructure stability, thermal stability, chemical stability, and mechanical reliability. Therefore, the substrate state, the chemical composition of the laser cladding coating and substrate, the processing parameters, and the interface comprise the critical factors which influence the microstructure and properties of the laser cladding coating prepared. How to systematically optimize the influencing factors and obtain well-balanced performance are long-term research issues.

Microstructure and Mechanical Properties of TiC/TiB Composite Ceramic Coatings In-Situ Synthesized by Ultrasonic Vibration-Assisted Laser Cladding

Laser cladding coating has many advantages in surface modification, such as a small heat-affected zone, and good metallurgical bonding. However, some serious problems such as pores, and poor forming quality still exist in the coating. To suppress these problems, a novel process of ultrasonic vibration-assisted laser cladding process was adopted to in-situ synthesize TiC/TiB composite ceramic coating on the surface of titanium alloy. Results showed that the introduction of ultrasonic vibration effectively improved the surface topography of the coating, reduced the number of pores in the coating, refined the crystal grains of the coating, decreased the residual tensile stress in the coating, and increased the micro-hardness of the coating. The tribological properties of the coating were significantly improved by the ultrasonic vibration, the wear resistance of the coating fabricated with ultrasonic vibration at power of 400 W increased about 1.2 times compared with the coating fabricated without ultrasonic vibration, and the friction coefficient decreased by 50%.

Effect of CeO2 on the microstructure and microhardensss of laser-cladded Ni60 on 35CrMoV alloys

In present work, the effect of CeO₂ addition on the crack susceptibility, microstructure, phase composition, solute segregation and microhardness of Ni60 cladding layer was investigated. The coatings were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and microscopic vickers hardness tester. The results show that main phase composition of Ni60 cladding layer are Ni₃Fe, Ni₃V, Ni₃B, Cr₂₃C₆, Fe₅C₂. The microhardness of the cladding layers from the surface to the substrate is gradually decreased with increasing depth of the cladding layer. With increasing addition of CeO₂, the diffraction peak of XRD is shifted to the left, indicating the lattice distortion in the phases of the coating. Compared with other cladding layers with different contents of CeO₂, the solute distribution of Ni60 cladding layer containing 4.0 % CeO₂ is more uniform, and the cross-section structure is more compact and homogeneous. The results show that the addition of 4.0 % CeO₂ can effectively inhibit the cracks and porosity, promote grain refinement, and improve the microstructure homogeneity in the Ni60 cladding layer.

Spectroscopic and structural properties of CeO2 nanocrystals doped with La3+, Nd3+ and modified on their surface with Ag nanoparticles

The purpose of this work is to present our efforts focused on applications of chemical synthesis of nanocrystalline cerium dioxide (CeO₂) powders doped with La³⁺ ions and CeO₂:Nd³⁺ modified, on their surface, with Ag nanoparticles (NPs). The synthesized powders were examined by X-ray powder diffraction (XRD), absorption, emission spectroscopy, scanning electron (SEM) and atomic force microscopy (AFM). The relations between crystallographic properties and stability of CeO₂ compounds doped by La ions and surface-modified by Ag were studied. XRD patterns revealed that all studied samples are single-phase and crystallized in the cubic fluorite-type structure, in space group Fm-3m. The average crystallite sizes estimated by Rietveld method of series: La-doped CeO₂ were in the range of 7–14 nm, and CeO₂:1%Nd³⁺/n-Ag (n: 1- 5wt.%) were found to be in the range of 29–34 nm, respectively. The lattice parameter a for La-doped CeO₂ powders varying from 5.416 to 5.482 Å with increasing content of La³⁺ ions from 0 to 20wt.%, respectively. For series of CeO₂:Nd³⁺/n-Ag materials lattice parameter a was at the same level and in accordance with the standard value a₀ = 5.411 Å (ICDD - 43-1002). The SEM and AFM observations depicted the grainy structure of all obtained CeO₂-powder samples. The estimated grain size ranged from 50 to 500 nm. The diverse grain shapes and packing was remarked in the samples. According to our knowledge, the relationship between the structural, spectroscopic and morphological characteristics of CeO₂ samples was presented in this work for the first time.

Effect of Graphene Oxide on the Performance of Co-Based Coatings on Ti6Al4V Alloys by Laser Cladding

In order to improve the hardness and wear resistance of Ti6Al4V alloys, Co-based coatings with different contents of graphene oxide (GO) were prepared on Ti6Al4V alloys by laser cladding. The effects of the graphene oxide content on the microstructure, hardness, and wear resistance were analyzed. It was found that carbides and undissolved graphene oxide films existed in the coating. Carbides contribute to grain refinement and improve the hardness of the coating. Graphene oxide films can improve the wear resistance of the coating. However, an excessive addition of graphene oxide affects the laser energy absorption of the coating. The results show that when the graphene oxide content is 0.5 wt.%, the performance of the coating is the best. Compared with the Co-based coating without graphene oxide addition, the hardness increased by 32.3%, the friction coefficient decreased by 27.2%, and the wear rate decreased by 66.5%.

Effect of CeO2 on Impact Toughness and Corrosion Resistance of WC Reinforced Al-Based Coating by Laser Cladding

WC reinforced Al-based coating with added CeO₂ was prepared on the surface of S420 steel by laser cladding. The microstructure and structure of the coatings were analyzed by scanning electron microscope, X-ray diffractometer and optical profiler. The mechanical properties and corrosion properties of the coatings were studied by microhardness tester, friction and wear tester, Charpy impact tester, and electrochemical workstation. The results show that the coating is mainly composed of Al-phase, continuous-phase, and hard reinforced-phase WC, and the coating and substrate show good metallurgical bonding. When the content of CeO₂ is 1%, the fine grain strengthening effect is obvious, and the impact toughness of the coating is obviously improved. Appropriate amount of rare earth CeO₂ can significantly improve the hardness of the coating. When the content of CeO₂ is more than 1%, the wear resistance of the coating decreases. The coating prepared with different CeO₂ content has higher impedance and corrosion resistance than that of the substrate. At 1% CeO₂ content, the coating has the best corrosion resistance.

Laser Cladding of Ti-Based Ceramic Coatings on Ti6Al4V Alloy: Effects of CeO2 Nanoparticles Additive on Wear Performance

Ti-based ceramic coatings on Ti6Al4V substrates were successfully prepared through a laser cladding process using pre-placed starting materials of TiCN + SiO2 mixed powder without or with adding a 3 wt % CeO2 nanoparticles additive, aiming at improving the wear resistance of the Ti6Al4V alloy for biological applications. The effects of the CeO2 nanoparticles additive on the microstructure, microhardness, and wear performance of the coatings were analyzed in detail. The observations showed that the main compositions of the cladding coating were TiCN and TiN phase. Compared to the coatings without CeO2, the coatings modified with CeO2 nanoparticles led to more excellent mechanical properties. The average microhardness of the coatings modified with CeO2 nanoparticles was approximately 1230 HV0.2, and the wear volume loss of the coatings modified with CeO2 nanoparticles was approximately 14% less than that of the coatings without CeO2 under a simulated body fluid (SBF) lubrication environment. The major reasons included that the microstructure of the coatings modified with CeO2 nanoparticles was refined and compact granular crystalline. The wear mechanisms of the coatings were investigated from the worn surface of the coatings, wear debris, and the worn surface of the counter-body balls. The wear mechanisms of the coatings without CeO2 included abrasive wear, adhesive wear, and fatigue wear, while the wear mechanisms of the coatings modified with CeO2 nanoparticles included only abrasive wear and adhesive wear, because the fine microstructure of the coatings had an excellent resistance to fatigue wear.