Investigation of Surface Modification of 60CrMoV18-5 Steel by EDM with Cu-ZrO2 Powder Metallurgy Green Compact Electrode

Electrical discharge machining (EDM) is a non-conventional machining process, which is mostly used for machining of difficult-to-cut materials. These materials are often used in engineering applications that require improved surface properties; thus, surface modification is desirable in these cases. In the recent past, it has been observed that EDM is an alternative surface modification process due to migration of material from the electrode to the workpiece surface. Surface modification can be done with powder metallurgy (P/M) electrode as tool. The aim of this work is to examine the surface modification of the tool steel Calmax (Uddeholm) by EDM process using Cu-30 wt.% ZrO2 P/M green compact electrode. The influence of peak current (Ip) and pulse-on (Ton) on the Material Transfer Rate (MTR) and Surface Roughness (SR) was investigated and the surface characteristics were also evaluated by scanning electron microscopy (SEM). The experimental results confirm the material migration from the electrode to the machined surface and show that the higher MTR of 46.5 mgr/min is achieved on the combination of Ip = 9 A and Ton = 25 μs and the Ra varies from 3.72 μm to 7.12 μm.

TAGUCHI GREY RELATIONAL MULTI-RESPONSE EXPERIMENTAL OPTIMIZATION ON MODIFICATION OF Al-6061 SURFACE USING Si–Cu GREEN COMPACT TOOL IN EDM

This paper presents the surface modification of aluminium-6061 by electric discharge machining (EDM). Si–Cu powder metallurgical green compact tool is used to deposit its material on to the work surface under reverse polarity of EDM. Compact load, current and pulse on-time are selected control parameters. Material deposition rate (MDR), tool wear rate (TWR) and surface roughness ([Formula: see text] are considered as process outputs. Scanning electron microscopic (SEM) analysis and energy dispersive X-ray (EDX) analysis show the presence of tool materials in the deposit of work surface. Olympus optical micrograph shows an average thickness of the deposited layer to be 18.73[Formula: see text][Formula: see text]m. The hardness of the deposited layer is found to be 268[Formula: see text]HV. Analysis of variance (ANOVA) shows the compact load to be the most effective parameter on surface modification followed by pulse on-time and current, respectively.

Comparative Study of the Properties of Cu-Cr-Mo System Electrical Contact Material by Sintering and Infiltration Methods

Contact materials in high-voltage vacuum interrupters require properties such as high conductivity, density and hardness to minimize arc heat damage. In this study, Cu–Cr–Mo alloy contact materials were examined for their usage as high-voltage contact materials. Ball milling was performed after analyzing the raw materials of the Cu, Cr and Mo powders. A green compact was produced using high pressure with a mixed powder. Subsequently, the composite was produced by sintering via the temperature and infiltration method according to the Cu content in the green compact. The composite sintering method produced a density of 8.55 g/cm3 (relative density 93%), a hardness of 217 HV and an electrical conductivity of 40.7% IACS at 1200 °C. The composite of 10 wt.% Cu produced by the Cu infiltration method exhibited a density of 8.7 g/cm3 (relative density 94%), hardness of 274 HV and electrical conductivity of 39 IACS% at 1300 °C. The measurements of the physical properties of our newly established method demonstrated a new possibility of using the Cu–Cr–Mo alloy as a contact material for high-voltage vacuum interrupters.

Determining the influence exerted by the static conditions of final squeezing on the compaction process of iron-based powder materials

This paper reports a study into the process of re-compaction of powder briquettes in the conditions of static pressing at a pressure of 800 MPa. The technological parameters of the pressing process have been analyzed, which make it possible to improve the compaction of powder briquettes based on iron. Such parameters are the outer greasing, which reduces friction between a green compact and the walls of the press tool matrix, and the firing, which removes the deformation strengthening of the green compacts and increases their plasticity. The green compacts’ sealing mechanism involved in the final squeezing process has been established, which is associated with the grinding of pre-compressed particles due to the strain in the contact areas. The increase in the stressed state of green compacts following the final squeezing was confirmed by the results of studying the residual micro-strains. The change in the stressed state of iron green compacts has been confirmed by the study into the structurally sensitive characteristics, which include the materials’ magnetic and electrical properties. Determining the magnetic characteristics has shown that final squeezing leads to an increase in coercive force, which can be explained by both the increase in the stressed state and the grinding of grains. Investigating the impact exerted by the annealing environment on the value of magnetic characteristics has demonstrated that annealing in hydrogen is more effective in terms of improving magnetic properties than annealing in a vacuum. This is due to the refining of grain boundaries through the processes of reduction of oxide films. The study of the mechanical characteristics of green compact materials based on iron powder has established that final squeezing leads to an increase in the hardness and strength of materials depending on the conditions of deformation. A significant improvement in the green compacts’ strength (820‒824 MPa) is due to both a decrease in porosity by 8‒10 % and an increase in the contact area as a result of plastic deformation after the annealing

A Comparative Study on the Properties of Cu-Cr-Mo System Electrical Contact Material by Sintering and Infiltration Method

The contact materials in high-voltage vacuum interrupter require properties such as high conductivity, high density, and high hardness to minimize arc heat damage. In this study, copper–molybdenum-chromium alloys contact materials are examined for a high voltage contact material. Ball milling process was carried out after analyzing the raw materials of copper, chromium, and molybdenum powders. A green compact was produced using a high press with the mixed powder. Afterwards, composite was produced by sintering method according to temperature and infiltration method according to Cu content in green compact. The composite of sintering method showed a density of 8.55 g/cm3 (relative density 93%) a hardness of 217 HV, and an electrical conductivity of 40.7 IACS% at 1200 °C. The composite of 10 wt.% Cu produced by the Cu infiltration method showed a density of 8.7 g/cm3 (relative density 94%), Hardness of 274HV and electrical conductivity of 39 IACS% at 1300 °C. The measurements of physical properties showed the new possibility of using the Cu–Cr–Mo alloy as a contact material for high-voltage vacuum interrupters.