Laser cladding technology enables the regeneration or manufacturing of machine parts with the improved surface layer properties. The materials applied during the laser cladding processes very often contain hard and wear-resistant tungsten carbide (WC) particles. However, the parts obtained after the laser cladding have usually unsatisfactory surface quality and thus require post-process finishing. In addition, the content of WC particles causes that clad layers are difficult to cut. Therefore, in order to improve their machinability, the laser-assisted machining (LAM) technology can be applied. Nevertheless, the material removal mechanisms during LAM of WC/NiCr clad layers are not recognized. Thus, this study is focused on the estimation of minimum uncut chip thickness and analysis of cutting forces which are important factors describing the chip decohesion process. The proposed method is based on the novel approach dedicated directly to the oblique cutting, considering the zeroth tangential force increment located onto rounded cutting edge. The experimental procedure involves cutting force component (F c , F f , F p ) measurements in the range of variable cutting conditions, as well as the cutting tool's micro-geometry inspection. On the basis of the measurements carried out, the force regression equations are formulated and subsequently applied to the determination of tangential force expression. Subsequently, the minimum uncut chip thickness is calculated on the basis of the equation derived from the zero tangential force increment condition and presented in function of cutting speed. The obtained results enable the effective selection of the cutting parameters during LAM of WC/NiCr clad layers.

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Abstract. The paper is focused on the evaluation of surface integrity formed during turning of Inconel 718 with the application of various laser assistance strategies. The primary objective of the work was to determine the relations between the applied machining strategy and the obtained surface integrity, in order to select the effective cutting conditions allowing the obtainment of high surface quality. The carried out experiment included the machining of Inconel 718 in the conventional turning conditions, as well as during the continuous laser assisted machining and sequential laser assistance. The surface integrity was evaluated by the measurements of machined surface topographies, microstructures and the microhardness. Results revealed that surface integrity of Inconel 718 is strongly affected by the selected machining strategy. The significant improvement of the surface roughness formed during machining of Inconel 718, can be reached by the application of simultaneous laser heating and cutting (LAM).

Abstract. The paper presents the discussion about the possibility of optimising heating and cutting parameters for turning under laser assisted machining (LAM) conditions. The samples of Inconel 718 after annealing and ageing were used. The laser heating experiments were carried out on the stand equipped with the CO2 molecular laser. Characterisation of samples was performed by an optical microscope, hardness measurements, scanning electron microscopy (SEM) to ensure the exact depth of heat affect zone range and to optimised further cutting parameters. Different absorbing layers for laser beam impact improvement were tested. Turning trials were performed with constant cutting speed vc = 28 m/min and feed f = 0,2 mm/rev. The influence of depth of cut ap on microstructure and its properties were investigated. It was proven that for sequential LAM dendritic structure appears in the laser affected zone of the Ni-based alloy. Such microstructures cause better machinability of Inconel 718 due to surface softening.

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