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

The transportation industry is no doubt a fast-
growing sector of the economy of most countries. As the world

population grows, there is a corresponding increase in the
demand for an improved and functional transportation system.
However, manufacturers and researchers in the automobile

industry face a lot of challenges in order to meet up with the ever-
increasing vehicle demand and government regulations. These

challenges include the need to develop a motor vehicle that would
be safe, economical and functional with low emission. Several
strategies towards the development of advanced materials have
been adopted to meet up with these challenges such as the
replacement of heavy metallic parts with high strength and
lightweight composite materials; and the use of nanoparticles as
additives in fuel, tyre, lubricants, coatings and paints. Titanium
as a material with low density, high rigidity, high corrosion
resistance, good thermal stability, high strength, structural
stability, and reflectivity together with epoxy resin which among
other thermosetting and conventional thermoplastic polymers
has improved mechanical, electrical, chemical and thermal
properties, as well as low shrinkage, low cost and high
compatibility with various reinforcing materials, have played
significant roles in this regard. This review, therefore, examines
the various applications of titanium and epoxy in the automobile
industry. They have successfully been applied in the manufacture
of lightweight parts, development of anti-fouling, anti-fogging,
self-cleaning, corrosion resistant, flame retardant, hydrophilic
and hydrophobic glasses, paints and coatings, efficient brake
system and lubricants, improved engine performance, enhanced
tyre and anti-microbial automobile interior components. This
paper highlights the enormous applications of Titanium and
epoxy in automobile.

Titanium and Epoxy for Automobile application: A Review

Most manufacturing processes such as machining, welding, heat treatment, laser forming, laser cladding and, laser metal deposition, etc. are subjected to a form of heat or energy to change the geometrical shape thus changing the inherent engineering and structural properties of the material. These changes often cause the development of locked up stresses referred to as residual stresses as a result of these activities. This study reports on the residual stresses developed due to the mechanical forming process to maintain a suitable structural integrity for the formed components. The result of the analysis through the X-ray diffraction confirmed that residual stresses were induced in the manufactured parts and further revealed that residual stresses were compressive in nature as found in the parent material but with values less than the parent material.

https://iopscience.iop.org/article/10.1088/1757-899X/328/1/012012/pdf

Investigating Resulting Residual Stresses during Mechanical Forming Process

Carbon steel is widely used in engineering applications due to its exceptional mechanical properties, and low cost. The fabrication technique employed to weld carbon steel plays a vital role in the final performance of the welded component when put into service. TIG welding is a generally accepted arc welding technique due to its ease and versatility coupled with its capacity to produce high-quality welds. It is the most desirable technique employed for welding plain carbon steel. This work aims to evaluate the influence of TIG welding process parameters on the mechanical and microstructural properties such as tensile strength, hardness, and microstructure of AISI 1008 carbon steel. The process parameters considered in this work were the TIG welding current, and gas flow rate. The tensile testing and the Vickers hardness testing have been carried out for the welded samples. The microstructural investigation was also carried out for the fusion zones (FZ) and the heat-affected zones (HAZ). The test results were analyzed, and emerging properties were compared for the various set of parameters. Welded specimen produced with 140 A, 15 L/mm had the highest hardness value. However, the highest average ultimate tensile strength of 432.89 MPA was produced from process parameters 180 A, 19 L/mm. Finer grain structures were seen in the fusion zones as compared to the heat-affected zones for all selected parameters.

Experimental Investigation of TIG-welded AISI 1008 Carbon Steel

This paper focuses on the microstructure evolution and the relationship to the microhardness profiling of the friction stir welded butt joint on similar AA6061-T6 Aluminium alloys The only parameters used and varied for this study were rotational speed and feed rate The geometry of the tool was kept constant and the material used was tool steel, W302 Friction stir welds were evaluated by both visual inspection and the X-ray digital radiography method Evaluation allowed for assessment of the weld integrity by examining for the presence and absence of weld defects The results indicated that the welds do not have any root defects The X-rays showed complete penetration as evidenced by the evaluation of microstructural joint interface

https://iopscience.iop.org/article/10.1088/1757-899X/413/1/012035/pdf

Evaluation of Friction Stir Welds by X-ray Digital Radiographic Non-Destructive Approach

The aim of this investigation is to characterize the effect of process parameters applied to the laser metal deposition of Al–Cu–Ti coatings on titanium substrate (Ti–6Al–4V). After the deposition process was completed, a new hybrid coated surface emerged with improvements in the following areas: improved thermal, mechanical, and metallurgical properties. During the laser metal deposition procedure to obtain a hybrid coating on Ti–6Al–4V, certain process parameters were employed to achieve the optimum results which are the scanning speed (1.0 m/min) and the laser power of the procedure, which was varied between 900 and 1000 W. The microstructural analysis was carried out using the scanning electron microscope (SEM) and an optical microscope (OPM). The mechanical properties of the samples were characterized using microhardness test.

Olawale S. Fatoba

Papers

Titanium and Epoxy for Automobile application: A Review

Investigating Resulting Residual Stresses during Mechanical Forming Process

Experimental Investigation of TIG-welded AISI 1008 Carbon Steel

Evaluation of Friction Stir Welds by X-ray Digital Radiographic Non-Destructive Approach

Effect of Process Parameters on the Hardness Property of Laser Metal Deposited Al–Cu–Ti Coatings on Ti–6Al–4V Alloy