In industries such as aerospace, petrochemistry and automobile, many parts of different machines are under environment which shows high temperature and high pressure, and have their proneness to wear and corrosion. Therefore, the wear resistibility and stability under high temperature need to be further improved. Nowadays, Laser cladding (LC) is widely used in machine parts repairing and functional coating due to its advantages such as lower dilution rate, small heat-affected zone and good metallurgical bonding between coating and substrate. In this paper, LC is introduced in detail from aspects of process simulation, monitoring and parameter optimization. At the same time, the paper gives a comprehensive review over LC material system as high entropy alloys (HEAs), amorphous alloy and single crystal alloy have been gradually showing their advantages over traditional metal materials in LC. In addition, the applications of LC in functional coatings and in maintenance of machine parts are also outlined. Also, the existing problems and the development trend of LC is discussed then.

Recent research and development status of laser cladding: A review

Additive manufacturing is an emerging technology that challenges traditional manufacturing methods. However, the corrosion behaviour of additively manufactured parts must be considered if additive techniques are to find widespread application. In this paper, we review relationships between the unique microstructures and the corresponding corrosion behaviour of several metallic alloys fabricated by selective laser melting, one of the most popular powder-bed additive technologies for metals and alloys. Common issues related to corrosion in selective laser melted parts, such as pores, molten pool boundaries, surface roughness and anisotropy, are discussed. Widely printed alloys, including Ti-based, Al-based and Fe-based alloys, are selected to illustrate these relationships, and the corrosion properties of alloys produced by selective laser melting are summarised and compared to their conventionally processed counterparts.

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Corrosion of metallic materials fabricated by selective laser melting

A systematic research into the cladding of stellite 6 on stainless steel by pulsed Nd:YAG laser has been carried out. The effects of pulse energy, pulse frequency, powder mass flow rate and spot overlap on the clad layer height, dilution and heat-affected zone (HAZ) have been examined. It was found that both the clad height and penetration into the substrate increase with the pulse energy, spot overlap and pulse frequency, but the effects of these parameters on dilution are complex. The dilution reaches the lowest value (4%) at the incident energy of 18 and 25 J/ pulse, spot overlap of 89% and pulse frequency of 40 Hz. The powder mass flow rate of 22 g/min (for energy of 25 J/pulse and spot overlap of 83%) produces thick clad layer with low dilution but results in the formation of defects. The hardness of the clad layer decreases linearly with increasing dilution. No cracks have been found in single-track clad layers at a spot overlap of 89%, however, cracks occurred at lower spot overlap. These cracks were eliminated by the multi-track cladding when the track increment is less than 1/3 of the width of track, which is believed to be due to the remelting or heat treatment of the previous clad track by the subsequent track. The track bands in multi-track clad show coarser structure, higher element segregation and lower hardness.

Pulsed Nd:YAG laser cladding of stellite 6 on stainless steel

Effect of TiC content on the mechanical and corrosion properties of Inconel 718 alloy fabricated by a high-throughput dual-feed laser metal deposition system

The marine, aerospace, and power machinery industries show progression in the application of titanium alloy components due to their good properties. However, the alloy exhibits poor thermal stability, low hardness, and poor tribological properties; as a result, the use of Ti6Al4V in various industries is restricted. Consequently, a search for surface improvement of Ti6Al4V alloy arose with the intention of enhancing its endurance. The use of laser metal deposition method by integrating chemical barrier coatings is considered as advantageous; therefore, an investigation aimed at surface improvement of Ti6Al4V by incorporation of Ti-Co coatings developed. To fabricate the coatings, a 3-kW continuous wave ytterbium laser system (YLS) was used, and to control the movement of the cladding process, a KUKA robot was attached to the system. The microstructure, corrosion, and mechanical properties of the titanium alloy-cladded surfaces were studied at different laser process parameters. To analyze the microstructure of the cross section, optical and scanning electron microscopy were employed. A laser power of 750 W and scanning rate of 1.2 m/min were found to be the optimum process conditions for a 60Ti-40Co alloy. When comparing the mechanical properties of the alloy and bare substrate, the alloy exhibited a significant increase in terms of the hardness. It was found to have 719 HV as compared to 301 HV which is that of the substrate, this indicates to an increase of 58.14% in the hardness. Lower laser scanning rates result in a larger fraction of hard-intermetallic phases which in turn lead to coatings with enhanced hardness levels. Furthermore, the yield strength and tensile strength of the coatings increased to maxima of 2.30 and1.66 GPa, respectively in comparison to the substrate, due to the addition of Co. Additionally, the corrosion rates of all the coated specimens were reduced as a result of the oxide films formed on the laser-coated Ti6Al4V alloy samples.

Evaluation of microstructure, microhardness, and electrochemical properties of laser-deposited Ti-Co coatings on Ti-6Al-4V Alloy

Corrosion and wear phenomenon has been responsible for the gradual deterioration of components in industrial plants. This deterioration of components results in loss of plant efficiency, total shutdown and aggressive damage in a number of industries. Hence, surface modification and coating technique with enhanced surface properties is desirable. The study was designed to investigate the enhancement in the corrosion, hardness and wear properties of Al-Sn binary coatings on AISI 1015 steel by laser alloying technique using ytterbium laser system (YLS). A laser power of 1000 W, scanning speeds of 0.6 and 0.8 m/min, and alloy compositions of Al-75Sn, Al-50Sn and Al-25Sn were used in this study. Decrease in Sn content from 75 to 25% at different laser processing conditions resulted in improved properties. The enhanced properties were obtained at 75Al-25Sn alloy at laser power of 1000 W and speeds of 0.6 and 0.8 m/min. At optimum composition and speed of 0.8 m/min, there was enhancement of 53.63% in microhardness. At scanning speed of 0.6 m/min, 75Al-25Sn alloy exhibited the highest polarization resistance, R
 p, (1.06 × 108 Ω cm2); lowest corrosion current density, I
 corr, (3.12 × 10−7 A/cm2); and lowest corrosion rate, C
 r, (0.00363 mm/year) in 3.65 wt% NaCl solution. In addendum, significant reduction in wear volume loss of 75Al-25Sn alloy at 0.8 m/min was attributed to excellent wear resistance performance due to metastable intermetallic phases. This research has established the enhanced surface properties of laser alloyed Al-Sn binary coatings on AISI steel for engineering applications.

Effects of rapid solidification on the microstructure and surface analyses of laser-deposited Al-Sn coatings on AISI 1015 steel

A review of the applications of fractal theory in modern manufacturing is presented in this chapter. A brief conceptual foundation, typical examples, and methods of computing fractals are summarized. The most common methods of computing fractal dimensions include box-counting, area-based measurements, and fractional Brownian motion (fBm) methods and have been briefly discussed along with the proposed improvements in the literature. It is noted that there are concerted efforts to improve on the known methods to enhance their accuracy and application in various fields. Finally, applications of fractals in thin films, laser processing, machining, and friction stir processes/welding are illustrated based on the published data. It is derived that fractal analysis is important in (1) understanding the growth of structures during different manufacturing processes (and parameters) and (2) developing fractal-like structures for enhanced performance in various engineering applications. Directions for future research and applications of fractal theory in manufacturing and their potentials are described in respective sections of the chapter. The chapter is a useful resource for academic and industry in studying, developing, and manufacturing of fractal-like engineering components and the interrelationships among the manufacturing process, parameters, and fractal characteristics of the engineering product.

Advances in manufacturing analysis: fractal theory in modern manufacturing

https://iopscience.iop.org/article/10.1088/2053-1591/aaca70/pdf

Microstructural analysis, micro-hardness and wear resistance properties of quasicrystalline Al–Cu–Fe coatings on Ti-6Al-4V alloy

Laser Additive Manufacturing is relatively new in the manufacturing industry. This paper focuses on the effect of hybrid coatings of Al-Cu-Fe on a grade five titanium alloy (Ti6Al4V) using laser metal deposition (LMD) process at different laser power and scanning speeds. Icosahedral Al-Cu-Fe as quasicrystals are a relatively new class of materials which exhibit unusual atomic structure and useful physical and chemical properties. Ti6Al4V/Al-Cu-Fe composite were analysed using Optical microscopy, Scanning electron microscopy (SEM) with energy dispersive microscopy (EDS), indentation testing, X-Ray Diffraction (XRD), corrosion and wear testing. deposit width and height, heat affected zone (HAZ) height), dilution rate, aspect ratio and powder efficiency of each sample remarkably increased with increasing laser power due to the laser-material interaction. It was observed that there are higher number of aluminium and titanium presented in the formation of the composite. The indentation testing reveals that for both scanning speed of 0.8m/min and 1m/min, the mean hardness value decreases with increasing laser power. It was found that due to dilution effect, a part of Ti entered into molten pool from the substrate. The results indicate that Ti, Al 3 Ti, Ti 3 Al, CuTi 2 can be produced through the in situ metallurgical reactions during the LMD process.

Olawale S. Fatoba

Papers

Evaluation of microstructure, microhardness, and electrochemical properties of laser-deposited Ti-Co coatings on Ti-6Al-4V Alloy

Effects of rapid solidification on the microstructure and surface analyses of laser-deposited Al-Sn coatings on AISI 1015 steel

Advances in manufacturing analysis: fractal theory in modern manufacturing

Microstructural analysis, micro-hardness and wear resistance properties of quasicrystalline Al–Cu–Fe coatings on Ti-6Al-4V alloy

Experimental investigation of laser metal deposited icosahedral Al-Cu-Fe coatings on grade five titanium alloy