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.
The technology of producing threads, especially in materials that are difficult to cut, is a rare subject of research and scientific publications. The requirements for the production of these elements apply not only to the geometry, but also to the quality of the surface obtained. This is particularly important in the aviation industry, where the durability of the threaded connection affects passenger safety. Due to the design of the thread, the quality of its surface is assessed visually in industrial practice. The authors of this study decided to examine the surface topography of external threads made by turning on Inconel 718 shafts in order to confirm the visual evaluation, as well as to investigate the influence of such factors as cutting speed, turning direction and type of profile. Three types of contours were cut for the research: triangular, trapezoidal symmetrical and trapezoidal asymmetrical. Turning of each was carried out twice at cutting speeds vc = 17 m/min and vc = 30 m/min. On each of the threads, the side surface of the profile made in the direction of the insert feed and the opposite surface were examined. The surface texture parameters Sa, Sq, Sp, Sv, Sz, Ssk and Sku were determined and compared. It was noticed that the thread surfaces show a tendency to irregular roughness, which was confirmed by the analysis of the Sku and Ssk coefficients. The sides of the contours made in the direction of the insert feed are characterized by a higher roughness in relation to the opposite sides, which may result from high cutting forces and difficulties with chip evacuation. With the cutting speed being considered, lower values of Sa and Sq were obtained for vc = 17 m/min, which differed from the visual assessment, proving its high subjectivity.
This paper applies to the tests of the machining of a part made of supper alloy – nickel alloy – Inconel 718, using a monolithic carbide cutter. The paper includes a different versions of cutting methods with variable cutting parameters and machining strategies. The used sustainable machining process allowed to obtain control over the tool wear.
This paper presents a comparison of surface morphology obtained after machining Inconel 718 by the conventional insert, by Wiper insert and by using the cutting insert made by Spark Plasma Sintering (SPS). The shape of the special insert was obtained by employing Wire Electrical Discharge Machining (WEDM). The paper focuses on the description of surface topography after turning in dry and wet conditions. The performed investigation included longitudinal turning tests of Inconel 718 performed in a range of variable feeds. Surface topography measurements have been performed with the application of Nanoscan 855. The performed analysis includes a parametric evaluation of the obtained surfaces. With the Wiper insert, the Sa surface roughness parameter was obtained below 0.6 µm in the whole range of used feed rates. The surface roughness parameter Sa measured on the surface after machining by special insert depends on the cutting conditions (wet and dry machining). After, the dry machining parameter Sa, similar to the Wiper insert, was below 0.6 µm in the whole range of used feed rates. Unfortunately, cutting Inconel 718 using special insert with feed rate f = 0.25 mm/rev and cooling generated a surface with Sa parameter over 2 times higher than for the same feed rate without cooling, while this parameter, after turning by conventional insert, increases over 4 times using feed rate f = 0.25 mm/rev compared to feed rate f = 0.05 mm/rev during machining with cooling. This ratio is lower for conventional insert in dry machining because of sticking, which arises at the smallest feed rate according to previous research.
Abstract. In the paper is presented analysis of chips morphology after turning of three groups of modern materials applied in aerospace industry: titanium alloys, stainless steels and heat resistant alloys. Various feed rates f and corner radiuses rε as well as recommended cutting speed vcfor given group of work material were applied in machining tests. Range of burrs on thinner edges of chips and serration on the chips surface occurrence were identified dependent on work material and uncut chip thickness (values of the f and rε). In the research height h and distance b between the burrs as well as distance a between serrated segments were measured. It was identified two kind of burrs connected with different physical phenomenon and specified h and b dimensions.
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