P. Nieslony

Microhardness and Surface Integrity in Turning Process of Duplex Stainless Steel (DSS) for Different Cutting Conditions

The objective of the investigation was to identify microhardness of surface integrity (SI) after turning with wedges of coated sintered carbide. SI is important in determining corrosion resistance, and also in fatigue crack initiation. The investigation included microhardness analyses in dry and wet machining of duplex stainless steel. The microhardness of SI for various cutting speeds was compared. It has been shown that wet cutting leads to the decrease of SI hardening depth, while increasing the rounded cutting edge radius of the wedge increases the maximum microhardness values and the hardening depth. An infinite focus measurement machine has been used for the rounded cutting edge radius analysis. The study has been performed within a production facility during the production of electric motor parts and deep-well pumps as well as explosively cladded sheets.Graphical Abstract

Structural and Microhardness Changes After Turning of the AISI 1045 Steel for Minimum Quantity Cooling Lubrication

This work presents the cooling effect under minimum quantity cooling lubrication and dry cutting on structural changes and microhardness of the ferritic-pearlitic AISI 1045 steel after turning. Due to the fact that the AISI 1045 steel has a two-phase structure, microhardness tests using the Vickers method were conducted with a load of 0.05 HV separately for ferrite and pearlite grains. The tests showed that cooling of the cutting zone under minimum quantity cooling lubrication (MQCL) condition decreased the depth of the hardened layer compared to dry cutting by approximately 40% for both pearlite and ferrite. Scanning electron microscopy analysis revealed that applying MQCL limits the formation of plastic deformations, among others, by reducing the surface crumple zone by approximately 50% compared to dry cutting. As a result of cooling being applied to the cutting zone using the MQCL method, the average diameter of ferrite grains has been decreased in the entire surface area compared to dry cutting. When using dry cutting, clear structural changes of the surface layer were also observed. This may be the result of sulfide inclusions which have formed, causing microcracks on the edge of the hardened layer and surface deformation visible as notches.

Topographic inspection as a method of weld joint diagnostic

The paper demonstrates a topographic inspection in the specific context of three kinds of inspection methods of austenitic stainless steel welds. Visual and metrological inspection was analysed during tungsten inert gas (TIG) welding tests, showing the non-destructive techniques: X-ray, computed tomography, and surface profilometry. The article is a response to the lack of information, especially in the area of non-destructive techniques suitable for wide practical application. The Paper presents advantages and drawbacks of the analysed diagnostic methods and a classification of conventional and specific welded joint flaws. The most important defect in practical applications determining reliability of a welded joint is cracks. This kind of diagnostic is based on the obtained information about anisotropic and inhomogeneous volume under consideration in the heat-affected zone of a weld.

Thermophysical-Property-Based Selection of Tool Protective Coatings for Dry Machining of Steels

A method is proposed for determining the optimum cutting conditions in dry turning of carbon and stainless steels using multilayer coated tools for physical criteria such as the maximum temperature of a cutting tool or maximum heat flux. The modified thermal number describing the tool-chip behavior, is introduced. The correlation between the thermal number and the average tool-chip interface temperature and frictional heat flux is examined for both flat-faced and grooved rake configurations. Although not shown here directly, the thermal barrier effect observed for multilayer coatings with an intermediate Al 2 O 3 layer increases the heat partition to the chip at substantially reduced cutting temperatures. The experimental results indicate that thermal and tribological outputs from the interface are sensitive to changes in the thermophysical properties of the workpiece and coating materials, in particular the thermal conductivity, thermal diffusivity and the heat transmission coefficient. It was proven that the described approach makes it possible to select the appropriate cutting conditions based on process constraints such as the heat transfer intensity and temperature on the tool face.

Forces and Process Dynamics in Profiling of AlCu4MgSi Aluminium Alloy

This work presents the results of experimental research regarding cutting force, chatter frequency and amplitude for different cooling conditions in profiling of AlCu4MgSi aluminium alloy. The following conditions were analyzed: dry cutting, cooling with water-based emulsion, MQL and MQCL. It was determined that cooling and lubricating conditions in the cutting zone have a minimal effect on machining forces in the following range of parameters: cutting speed 300–600 m/min, depth of cut 1–2 mm, feed rate 0.1–0.5 mm/rev. Therefore, a conclusion to introduce dry machining to cut down costs was formed. Changes in cutting force components can be described by the following relation: Fc ≈ Fp > Ff. The intensity of the effect of technological parameters on cutting force components decreases in the direction of f → ap → vc. It was proven that by analyzing changes of cutting force in machining time, possibilities of chatter occurrence for different machining conditions can be assessed.

Investigation of the Effect of Process Parameters on Surface Roughness in EDM Machining of ORVAR® Supreme Die Steel

This work presents the effect of selected process parameters on surface roughness in EDM machining of hot-working die steel. Different values of pulse current and pulse voltage were assumed in combination, while individual pulse time was set as constant. The effect of EDM parameters on 3D surface roughness parameters was investigated. Two samples machined with different pulse voltages were prepared, with each sample divided into five separate areas corresponding to different values of used pulse current. 3D surface roughness measurements were performed on each area of all samples. The authors have found a substantial link between pulse current and surface roughness. Moreover, it was discovered that pulse voltage affects surface roughness in a significant way for a certain range of pulse current values, allowing to obtain better surface finish with the use of a higher voltage.

Investigation of Heat Distribution in Coated Indexable Tool Inserts

Article presents the results of temperature changes and heat distribution in a cemented carbide indexable tool insert with a TiAlN coating. The study presented in the article focused on heat distribution in a cutting tool–chip interface in two special cases: when a heat source is in contact with the TiAlN tool coating and when the heat source is in direct contact with a substrate plate. The thermophysical formulas were applied to both of them. The change of heat flux as a function of the distance from the heat source contact point along with experimental data was examined. The experimental data for the heat propagation in the cutting tool point have been gathered using an authors’ test stand.

The effect of changes in depth of cut and cutting speed of CNC toolpaths on turning process performance

Abstract In this article, a novel approach to computer optimization of CNC toolpaths by adjustment of cutting speed vcand depth of cut apis presented. Available software works by the principle of adjusting feed rate on the basis of calculations and numerical simulation of the machining process. The authors wish to expand upon this approach by proposing toolpath optimization by altering two other basic process parameters. Intricacies and problems related totheadjustment of apand vcwere explained in the introductory part. Simulation of different variant of the same turning process with different parameter values were conducted to evaluate the effect of changes in depth of cut and cutting speed on process performance. Obtained results were investigated on the account of cutting force and tool life. The authors have found that depth of cut substantially affects cutting force, while the effect of cutting speed on it is minimal. An increase in both depth of cut and cutting speed affects tool life negatively, although the impact of cutting speed is much more severe. An increase in depth of cut allows for a more significant reduction of machining time, while affecting tool life less negatively. On the other hand, the adjustment of cutting speed helpsto reduce machining time without increasing cutting force component values and spindle load.

Effect of Heat Treatment on Mechanical Properties of Inconel 625/Steel P355NH Bimetal Clad Plate Manufactured by Explosive Welding

In this investigation, steel P355NH was successfully cladded with Inconel 625 through the method of explosive welding. Explosively welded bimetal was subjected to the two separated heat treatment processes: stress relief annealing (at 620 °C for 90 min) and normalizing (at 910 °C for 30 min). In order to examine the quality of joint and effects of heat treatments, the mechanical properties of the obtained samples were evaluated by tensile test, shear test, Charpy impact test and bend test. It was found that tensile strength of explosively welded bimetal is higher than tensile strength of the base material in the as-received state. Compared to the bimetal clad plate without heat treatment, bimetal subjected to the stress relief annealing has improved mechanical properties. It was stated that stress relief annealing is recommended heat treatment for Inconel 625/steel P355NH bimetal clad plate obtained by explosive welding.

Topographic inspection as a method of weld joint diagnostic [Topografsko ispitivanje kao metoda za dijagnosticiranje stanja zavarenog spoja]

The paper demonstrates a topographic inspection in the specific context of three kinds of inspection methods of austenitic stainless steel welds. Visual and metrological inspection was analysed during tungsten inert gas (TIG) welding tests, showing the non-destructive techniques: X-ray, computed tomography, and surface profilometry. The article is a response to the lack of information, especially in the area of non-destructive techniques suitable for wide practical application. The Paper presents advantages and drawbacks of the analysed diagnostic methods and a classification of conventional and specific welded joint flaws. The most important defect in practical applications determining reliability of a welded joint is cracks. This kind of diagnostic is based on the obtained information about anisotropic and inhomogeneous volume under consideration in the heat-affected zone of a weld.