High-temperature thermo-mechanical processing (HTTMP) is a combination of plastic deformation and heat treatment operations. Such action makes it possible to increase metal mechanical properties resulting from both mechanical strengthening and heat treatment. As a result, it is possible to achieve high complex of operating characteristics of different types of steel and other alloys. However, there is a lack of information on the applicability of HTTMP of powder steel. These types of steel are very effective substitutes for traditional structural steel but are characterized by poor mechanical properties. This study considers the possibility of using HTTMP for powder steel frame additionally infiltrated by bronze with MoS2 addition to increase mechanical properties of the materials studied. Steel infiltrated, infiltrated and then hardened, infiltrated and then HTTMP treated with strain rates of 30, 50 and 70% were compared. The microstructural properties and hardness of the materials before machining were studied as well as the cutting forces and surface topography of those materials after turning with AH8015 carbide inserts. Cutting forces tests were realized with vc = 157 m/min, f = 0.25 mm/rev and ap = 0.25 mm. Surface topography tests were carried out with vc = 157 m/min, f = 0.25 mm/rev and ap = 0.25 mm. Constant cutting parameters were used to eliminate the effects of rest factors. It was found that the lowest cutting forces (Fc, Fp and Ff), surface roughness parameters (Sa and Sq) and small areas with single high peaks on the machined surface were obtained for infiltrated powder steel with subsequent HTTMP machining under 50% strain rate.
This paper describes findings in the surface topography of Ti6Al4V alloy after finish turning process under dry and MQL (minimum quantity lubrication) machining. The research was fulfilled in the range of variable feeds per revolution of 0.005-0.25 mm/rev and cutting speeds of 40-100 m/min using the depth of cut of 0.25 mm that fits finish processing conditions. The test plan was developed on the way to use the Parameter Space Investigation (PSI) method. The topography features were measured by a Sensofar S Neox optical profilometer using the Imaging Confocal Microscopy technique. Ra parameters and surface roughness profiles as well as 2D images and contour maps were analyzed. Under the studied machining conditions, lower Ra roughness parameters are obtained in the feed rate of 0.005-0.1 mm/rev and cutting speeds of 40-60 m/min. In comparison with dry machining, up to 17% reduction in Ra parameter values was obtained using the MQL method and vc = 70 m/min and f = 0.127 mm/rev as well as vc = 47.5 m/min and f = 0.22 mm/rev. Depending on the machining conditions, peaks and pits as well as feed marks typical for the turning process are observed on the machined surfaces.
Titanium alloys belong to the group of difficult-to-cut materials, machining of which leads to a number of challenges including large thermal loads on the cutting inserts and difficulties in obtaining a high quality machined surface. Great cutting forces, in turn, result in increased energy consumption. Therefore, it becomes important to attempt to reduce the amount of power consumed during machining, which can be achieved, among other things, by reducing the value of the coefficient of friction in the cutting zone. This paper presents a study on the influence of the size as well as the Cu nanoparticle concentration added to cutting fluid in MQL method on the power grid parameters while turning of Ti6Al4V titanium alloy. In this research, nanoparticles of 22 nm and 65 nm at concentrations of 0.5 wt% and 0.75 wt% were used. Turning process was carried out with constant cutting parameters and variable aerosol formation parameters, i.e. mass flow rate of nanofluid and volumetric flow rate of air. Based on the study, the use of 22 nm nanoparticles at 0.5 wt% concentration is recommended to achieve the smallest monitored values of the power grid parameters. The statistical analysis revealed that, out of the aerosol formation parameters considered, both the air flow rate and nanofluid flow rate do not significantly affect the values of the analysed power network parameters. However, the most significant factor is the variable nanoparticle size.
The shape and type of chip give general information about the cutting process. This paper presents the results of testing the shape and type of chips of Ti6Al4V titanium alloy after it finishes turning. The process was carried out under dry, wet and MQL (Minimum Quantity Lubrication) conditions at variable cutting speeds and feed rates and a constant depth of cutting. For planning the tests, the PSI (Parameter Space Investigation) method was used, which allows the experiment to be carried out while minimizing the number of experience points. It was found that the cutting speed and feed affect the type and shape of the chip, and clear differences were observed between dry and wet cooling conditions, and MQL conditions. During turning, the intensity of the cutting speed and feed influence on the chip compression ratio was changed. It was similar for dry and wet cooling conditions but smaller for MQL conditions. The purpose of this research is to analyze the chip shaping when Ti6Al4V titanium alloy finishes turning under dry, wet and MQL cooling conditions.
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