Abstract:Usually, the surface quality of components produced under turning of particle reinforced metal matrix composites (PRMMCs) is one of the most important factors influencing their practical performance. Keeping good surface quality needs additional manufacturing cost or loss of productivity. In this study, semi-finish turning tests were conducted using high-power diode laser and cemented carbide tools to evaluate the superiority of the laser-assisted machining of PRMMCs and better understand its governing mechani… Show more
“…In this study, the highest relative density for the sample was expected. Thus, the "higher is better" category was adopted, which can be calculated as follows [30]:…”
The preparation of refractory tungsten and tungsten alloys has always been challenging due to their inherent properties. Selective laser melting (SLM) offers a choice for preparing tungsten and tungsten alloys. In this work, 90W-7Ni-3Fe samples were prepared by selective laser melting and investigated. Different process parameter combinations were designed according to the Taguchi method, and volumetric energy density (VED) was defined. Subsequently, the effects of process parameters on densification, phase composition, microstructure, tensile properties, and microhardness were investigated. Nearly a full densification sample (≥99%) was obtained under optimized process parameters, and the value of VED was no less than 300 J/mm3. Laser power had a dominant influence on densification behavior compared with other parameters. The main phases of 90W-7Ni-3Fe are W and γ-(Ni-Fe), dissolved with partial W. In addition, 90W-7Ni-3Fe showed a high tensile strength (UTS = 1121 MPa) with poor elongation (<1%). A high average microhardness (>400 HV0.3) was obtained, but the microhardness presented a fluctuation along building direction due to the inhomogeneous microstructure.
“…plasma, gas torch, electrical current heating). Laser assisted machining (LAM) has been reported to offer many advantages, such as reducing cutting forces [13,14] and specific machining energy [15,16], suppressing chatter [17], increasing material removal rates [18], extending tool life [19,20], minimizing residual stresses [21,22], generating crack-free machined surfaces [23], and diminishing environmental impact [24]. Accordingly, the LAM process is a very promising way to make these difficult-to-cut materials easier to machine [25].…”
Laser assisted machining (LAM) is one of the most efficient ways to improve the machinability of difficultto-cut materials (e.g. Nickel-based superalloys). In the conventional LAM process, the laser beam is focused ahead of the cutting area at a fixed location, which leads to a series of restrictions, e.g. small heating area and non-uniform heat distribution due to the limitation of beam size and energy distribution. In this paper, a novel spatially and temporally (S&T) controlled laser heating method was proposed, in which a large area can be heated up with a small laser spot by controlling the beam scanning, i.e., laser power, path and speed of scanning. The laser configuration for the prescribed HAZ (heat affected zone) was achieved by solving the inverse problem where the laser power together with either laser path or laser speed were optimised to achieve a particular temperature distribution in the chip to be removed by the following milling cutter. The proposed S&T laser heating method was thoroughly validated both for the forward and, the more important, inverse heating models by performing extensive temperature experiments by both infrared thermal camera and thermocouple array and further verified by laser assisted milling (LAMill) tests of Inconel 718 for large widths of cuts. The results showed that by applying path-optimised LAMill based on the inverse solution of the thermal problem, the peak and mean principal cutting forces were reduced by 55% and 47.8% respectively compared with the conventional dry milling process while the surface roughness improved by at least 14%. Moreover, after controlling the HAZ using the inverse thermal problem, a microstructure analysis of the machined surface showed that the proposed laser heating method avoids overheating of the workpiece below the planned depth of cut for the milling operation.
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