Erosion resistance of laser clad Ti-6Al-4V/WC composite for waterjet tooling

AbstractIn waterjet operations, milled surfaces are left with some undesirable dimensional artefacts, thus the use of abrasion resistant mask has been proposed to improve the surface quality of machined components. In this study, the erosion performance of laser clad Ti-6Al-4V/WC composite coating subjected to plain water jet (PWJ) and abrasive water jet (AWJ) impacts to evaluate its potentials for use as waterjet impact resistant mask material and coating on components was investigated. Results showed that composite with 76wt.% WC composition subjected to PWJ and AWJ impacts offered resistance to erosion up to 13 and 8 times that of wrought Ti-6Al-4V respectively. Scanning electron microscopy (SEM) examination of the eroded composite surfaces showed that the erosion mechanism under PWJ impacts is based on the formation of erosion pits, tunnels and deep cavities especially in the interface between the WC particles and the composite matrix owing to lateral outflow jetting and hydraulic penetration. Composite suffered ploughing of the composite matrix, lateral cracking and chipping of embedded WC particles and WC pull-out under AWJ impacts. The composite performance is attributed to the embedded WC particles and the uniformly distributed nano-sized reaction products (TiC and W) reinforcing the ductile β-Ti composite matrix, with its mean hardness enhanced to 6.1GPa. The capability of the Ti-6Al-4V/WC composite coating was demonstrated by effective replication of a pattern on a composite mask to an aluminium plate subjected to selective milling by PWJ with an overall depth of 344μm. Thus, composite cladding for tooling purpose would make it possible to enhance the lifetime of jigs and fixtures and promote rapid machining using the water jet technique

Development of metal matrix composites by direct energy deposition of ‘satellited’ powders

Limited research has been undertaken investigating the material design freedoms that are granted through the use of additive manufacturing methods, especially in the development of materials specifically formulated for additive processes. In this study, a new material combination was evaluated for use with directed energy deposition methods of additive manufacturing. Here, a Ti-6Al-4 V powder is processed in combination with a much finer titanium diboride powder following a satelliting procedure. The resulting combination consists of large Ti-6Al-4 V particles encased in finer titanium diboride. Deposited composites presented exhibit TiB needles associated with increased hardness. Processing conditions were detailed which permit the deposition of the prepared feedstock onto Ti-6Al-4 V substrates. Microstructural characterisation revealed that the composite was made up of eutectic TiB precipitates dispersed in α-β Ti matrix with few partially melted Ti-6Al-4 V and TiB2 particles. Satelliting TiB2 powder onto Ti-6Al-4 V particle surfaces has significantly improved the homogeneity of composite which is characterised with randomly oriented and uniform distribution of TiB needles in the microstructure. Hardness of composites ranged between 440–480 HV. Hence, the feedstock preparation method proposed has been found to be effective and can be adapted for low cost and rapid formulation of a host of materials for processing by additive manufacture

Functionally graded Ni-Ti microstructures synthesised in process by direct laser metal deposition

The fabrication of biomedical devices using Ni-Ti compositions is limited to conventional techniques and the use of near equiatomic pre-alloyed Ni and Ti powders. In this study, functionally graded walls and cylinder built by concurrent feeding of Ni powder and commercially pure (CP) Ti wire using direct laser metal deposition technique are presented. The built structures consist of CP Ti wire-deposited layers and Ni-Ti layers of varying Ni composition. The microstructures of the built Ni-Ti structures including phase identification, phase compositions and area fractions of the phases present at various processing parameters were determined using a combination of scanning electron microscopy/ energy dispersive X-ray spectroscopy, X-ray diffractometry and image processing software. Vickers microhardness test was conducted on the deposited structures. It was found that the Ni-Ti layers comprise of NiTi and NiTi2 phases. The area fraction of the NiTi phase increases, whereas NiTi2 decreases with increasing the Ni powder feed rate. Ni-Ti layers with higher area fractions of NiTi2 phase are found to be harder with a maximum of 513 HV0.3 found in this study. The micro-hardness of Ni-Ti layers is, by at least a factor of 1.5, higher than the CP Ti wire laser-deposited layers

Wire arc additive manufacturing of aluminium alloys for aerospace and automotive applications:A review

Wire arc additive manufacturing (WAAM) is suitable for printing medium-to-large complex parts with structural integrity while reducing material wastage, and lead time, improving the quality and customized design for functional components. Aluminium alloys are one of the most commonly used metallic materials in manufacturing parts for aerospace and automotive applications due to their lightweight, excellent strength, and corrosion resistance properties. Aluminium alloys have been employed in the WAAM process to produce parts for the aerospace and automotive industries. In this paper, various research works associated with the application of WAAM of aluminium alloys for aerospace and automotive industries, their metallurgical characteristics, and mechanical properties have been reviewed and discussed in detail to identify the research gap and future research directions. This paper is patterned to provide a comprehensive review of WAAM of aluminium alloys for the production of parts in the aerospace and automotive industries

Wire arc additive manufacturing of aluminium alloys for aerospace and automotive applications:A review

Wire arc additive manufacturing (WAAM) is suitable for printing medium-to-large complex parts with structural integrity while reducing material wastage, and lead time, improving the quality and customized design for functional components. Aluminium alloys are one of the most commonly used metallic materials in manufacturing parts for aerospace and automotive applications due to their lightweight, excellent strength, and corrosion resistance properties. Aluminium alloys have been employed in the WAAM process to produce parts for the aerospace and automotive industries. In this paper, various research works associated with the application of WAAM of aluminium alloys for aerospace and automotive industries, their metallurgical characteristics, and mechanical properties have been reviewed and discussed in detail to identify the research gap and future research directions. This paper is patterned to provide a comprehensive review of WAAM of aluminium alloys for the production of parts in the aerospace and automotive industries

Surface improvement of laser clad Ti-6Al-4V using plain waterjet and pulsed electron beam irradiation

© 2014 The Authors. Laser cladding is a flexible process which can be used to enhance the lifetime of components and repair them when worn. This is especially relevant where components are highly valued, and therefore costly to replace. To date, the surface finish achievable by laser cladding is poor and is characterised by ridges which correspond to the individual beads associated with the process. Increasingly laser cladding is being applied to conformal surfaces which are difficult to process by conventional grinding procedures which may also be ineffective because of discontinuous clad regions. There is therefore a need for a freeform approach which is capable of introducing specific surface finishes to complex components. Hence, in this study, a process chain incorporating plain water jet (PWJ) followed by a pulsed electron beam irradiation was used for the surface modification of laser clad surfaces of Ti-6Al-4V. Initially the surface was characterised by large recesses with peak-trough heights of 200 ± 18 μm and waviness of 49 μm. Upon processing employing water head pressure of 345 MPa impinging the clad surface at an angle 90°, 250 mm/min jet traverse speed, 3 mm stand-off distance and 0.25 mm milling overlap with 2 passes, it was possible to eliminate the peak-trough profile by milling to a depth of 480 ± 10 μm. A flat surface characterised by a surface waviness of 14.9 μm, 12.6 μm Ra and 44 μm straightness was achieved. PWJ milled surfaces were characterised by deep cavities, stepped fractured surfaces, cracks and sub-surface tunnels, however, with application of pulsed electron beam irradiation, most of these surface features were eliminated with a relatively smooth surface produced with 6.2 μm Ra finish