Search Results (3)

High thermal conductivity steel (HTCS-150) is deposited onto non-heat-treated AISI H13 (N-H13) via powder-fed direct energy deposition (DED) based on the response surface methodology (RSM) to enhance the mechanical properties and thermal conductivity of N-H13, which is generally used as a hot-work tool steel. The main process parameters of the powder-fed DED are priorly optimized to minimize defects in the deposited regions and, therefore, to obtain homogeneous material properties. The deposited HTCS-150 is comprehensively evaluated through hardness, tensile, and wear tests at the different temperatures of 25, 200, 400, 600, and 800 °C. Compared to conventionally heat-treated (quenched and tempered) H13 (HT-H13), the hardness of the additively manufactured HTCS-150 slightly increases at 25 °C, whereas it does not show any significant difference above 200 °C. However, the HTCS-150 deposited on N-H13 shows a lower ultimate tensile strength and elongation than HT-H13 at all tested temperatures, and the deposition of the HTCS-150 on N-H13 enhances the ultimate tensile strength of N-H13. While the HTCS-150 does not show a significant difference in the wear rate below 400 °C compared to HT-H13, it shows a lower wear rate above 600 °C. The HTCS-150 reveals a higher thermal conductivity than the HT-H13 below 600 °C, whereas the behavior is reversed at 800 °C. The results suggest that the HTCS-150 additively manufactured via powder-fed direct energy deposition can enhance the mechanical and thermal properties of N-H13, including hardness, tensile strength, wear resistance, and thermal conductivity in a wide range of temperatures, often superior to those of HT-H13. Full article

The industrial application of electrical discharge machining (EDM) for manufacturing injection molding, in many cases, requires forming depth cavities with high length-to-width ratios, which is quite challenging. During slot EDM with thin-walled electrodes, short-circuits and arcing discharges occur, as a result of low efficiency in removing debris and bubble gas from the gap. Furthermore, unstable discharges can cause increases in tool wear and shape deviation of the machined parts. In order to characterize the influence of the type of electrode material and EDM parameters on the deep slot machining of high-thermal-conductivity tool steel (HTCS), experimental studies were conducted. An analytical and experimental investigation is carried out on the influence of EDM parameters on discharge current and pulse-on-time on the tool wear (TW), surface roughness (Ra), slot width (S)—dimension of the cavity, and material removal rate (MRR). The analyses of the EDS spectrum of the electrode indicate the occurrence of the additional carbon layer on the electrode. Carbon deposition on the anode surface can provide an additional thermal barrier that reduces electrode wear in the case of the copper electrode but for graphite electrodes, uneven deposition of carbon on the electrode leads to unstable discharges and leads to increase tool wear. The response surface methodology (RSM) was used to build empirical models of the influence of the discharge current I and pulse-on-time t_on on Ra, S, TW, and MRR. Analysis of variance (ANOVA) was used to establish the statistical significance parameters. The calculated contribution indicated that the discharge current had the most influence (over 70%) on the Ra, S, TW, and MRR, followed by the discharge time. Multicriteria optimization with Derringer’s function was then used to minimize the surface roughness, slot width, and TW, while maximizing MRR. A validation test confirms that the maximal error between the predicted and obtained values did not exceed 7%. Full article

New materials require the use of advanced technology in manufacturing complex shape parts. One of the modern materials widely used in the tool industry for injection molds or hot stamping dies is high conductivity tool steel (HTCS) 150. Due to its hardness (55 HRC) and thermal conductivity at 66 W/mK, this material is difficult to machine by conventional treatment and is being increasingly manufactured by nonconventional technology such as electrical discharge machining (EDM). In the EDM process, material is removed from the workpiece by a series of electrical discharges that cause changes to the surface layers properties. The final state of the surface layer directly influences the durability of the produced elements. This paper presents the influence of EDM process parameters: discharge current I_c and the pulse time t_on on surface layer properties. The experimental investigation was carried out with an experimental methodology design. Surface layers properties including roughness 3D parameters, the thickness of the white layer, heat affected zone, tempered layer and occurring micro cracks were investigated and described. The influence of the response surface methodology (RSM) of discharge current I_c and the pulse time t_on on the thickness of the white layer and roughness parameters Sa, Sds and Ssc were described and established. Full article