Metal spray layered hybrid additive manufacturing of PLA composite structures: Mechanical, thermal and morphological properties

The fusion of additive layers is the primary concern, which affects the mechanical properties of the three-dimensional printed structures prepared by material extrusion-based additive manufacturing (MEAM) process. To promote the fusion and strength between the thermoplastic layers during MEAM process, the metal spray in between the additive layers is used as a novel approach. In this study, aluminium (Al) spray has been deposited in between the polylactic acid structures to enhance the bonding of the additive layers. The methodology includes deposition of 1, 3 and 5 Al spray layers at periodic time intervals with varying infill percentage (40%, 70% and 100%) and bed temperature (60°C, 80°C and 100°C). The structures have been subjected to flexural testing for investigation of the role of each input process parameter followed by fracture morphology analysis through scanning electron microscopy and energy-dispersive spectroscopy. The results of the study suggested that the maximum flexural strength is possible with five spray layers, 70% infill and 100°C bed temperature.

Low-pressure cold metal spray coatings for repair and protection of marine components

The marine environment is hostile to most engineering materials, a combination of in-service wear and exposure to marine environment leads to an accelerated material degradation. Insufficient or poor protection of the substrates further assists the accelerated material degradation in marine environment. There is a direct relationship between the material-state of a ship and its operational capability, readiness, and service life. The current state-of-the-art practice is to use paint-based coatings to maintain the material-state of ships. However, the protection offered by paint coatings is usually brief due to inherent permeability and low damage tolerance of these coatings. For this reason, the paint coatings require renewal at regular intervals, typically less than 5-years, to maintain a minimum level of protection from the marine environment. The need for regular painting of ships results in a significant negative impact on the through-life availability, operational capability/readiness, and the cost of maintenance/operation of naval ships. Therefore, the fleet owners and operators should look beyond the conventional paint-based coatings to achieve significant breakthrough improvements in maintaining and enhancing the material-state of naval ships. Metallic coatings, if selected and applied appropriately, will outperform the paint coatings in the marine environment. Historically, the cost and performance of metallic coatings, mainly thermal metal spray (TMS) coatings, prevented their widespread use in the marine industry. The TMS coatings also have their own inherent application and performance related limitations that are widely reported in the literature. However, the cold metal spray (CMS) coating process can overcome the application and performance related limitations that are typically associated with the TMS coatings, therefore creating an opportunity for widespread use of metallic coatings in shipbuilding and fleet upkeep/maintenance. In this paper, the ability of low-pressure (LP-CMS) coatings to repair and reclaim damaged marine components, and application of functional coatings to improve in-service damage tolerance of the damaged/new components is investigated. The results of the investigation show that two LP-CMS coatings, Al-alloy and CuZn-alloy, can be used to repair and preserve both new and damaged components. The accelerated salt-spray and natural immersion corrosion testing of the LP-CMS coatings showed that each coating will be better suited to a particular operational environment, i.e. CuZn-alloy coating performed well in both immersion and atmospheric corrosion environments, whereas Al-alloy coating performed well only in atmospheric corrosion environment.

Cyclic Oxidation Performance of Si-Aluminide/MCrAlY Coating on Ni-Base GTD-111 Superalloy

A slurry aluminising process was utilised to produce duplex Si-modified aluminide MCrAlY coatings for superalloy GTD-111. MCrAlY coating was applied by means of high velocity oxy-fuel (HVOF) metal spray technique. Cyclic oxidation behaviour of the aluminide/MCrAlY coating were compared with plain MCrAlY coating. Oxidation performance of the coated samples was investigated by exposing samples to 1 h cyclic oxidation at 1100 °C. Oxidation test results demonstrate the Si-aluminide/MCrAlY coating exhibited much better oxidation resistance than the the uncoated superalloy due to the superior oxidation resistance of the alumina-silica scale at 1100 °C.

Arc thermal metal spray for the protection of steel structures: an overview

Coating for corrosion protection was popular during the past decade. Thermal spray coating played an important role during that time. In recent years, arc thermal metal spray coating became widely used. Arc thermal metal spraying method (ATMSM) provides proven long-term protective coating systems using zinc, aluminum, and their alloys for steel work in a marine environment. This paper provides a review of the latest development in ATMSM by evaluating the current techniques in the industry and by analyzing technical data obtained from an extensive experimental program.