Adem Kurt

Effect of Porosity Content on the Weldability of Powder Metal Parts Produced by Friction Stir Welding

Friction stir welding technique (FSW) has many advantages in terms of tool design, rotational speed and traveling speed, and can be adjusted in a precise manner. It enables heat input into the system to be controlled. In this study, Aluminum powders were compacted at 350,400 and 450 MPa pressure and sintered at 450 oC temperature for 30 minutes in Ar atmosphere. Sintered powder metal parts were joined to each other by FSW at the speed of 1800 rpm and traveling welding speed 200 mm/min under a constant friction force. The results show that the amount of porosity affects the weldability of powder metallurgy (P/M) parts. Furthermore, the porosity and microstructural evolution of the Aluminum also affected the hardness values of the tested materials.

The Experimental Investigation of the Effects of Different Chip Breaker Forms on the Cutting Forces

The objective of this paper is experimentally investigation of the effects of different chip breaker forms on the cutting forces according to various cutting parameters. AISI 1050 workpiece material, most used material in the manufacturing industry, and SNMG 120408R inserts and PSBNR 2525M12 tool holder have 75° approaching angle according to ISO 3685 are used in the experiments. Seven groups chip breaker form were used in the tests. The chip breaker forms are the coated inserts MA, SA, MS, GH and standard, and the uncoated inserts MS and standard. These inserts are Mitsubishi UC 6010 and UTI20T grade; correspond to ISO P30 and P15 grade, respectively. Machining tests were carried out by using five levels of cutting speeds (150, 200, 250, 300, 350 m/min), three levels of feed rate (0.15, 0.25, 0.35 mm/rev) and two levels of depth of cut (1.6, 2.5 mm). Cutting forces were measured using Kistler dynamometer. The test results show that the highest cutting force values were measured on SA, GH, MA forms, respectively. Complex chip breaker forms cause the increase of the cutting forces. Although the cutting forces on the uncoated inserts were partly small in light cutting conditions, it has increased on the uncoated inserts in heavy cutting conditions compared to coated inserts.

Effects of Temperature on the Weldability of Powder Metal Parts Joined by Diffusion Welding

Diffusion welding is an advanced bonding process in which similar or dissimilar materials can be bonded in solid state. In this study, aluminium composite (5% and 15% WC) powders were compacted at 450 MPa pressure and sintered at 550 oC for 45 minutes in argon atmosphere.and joined each other by diffusion bonding. The bonding temperatures (585 oC, 600 oC, 615 oC) and dwell time (185 min) were chosen for the welding process at constant 20 MPa. It has been observed that these variations on the welding parameter strongly affected the microstructure and the weldability of the materials.

Investigation of Weldability of P/M Bronze Materials by Tig Welding Technique

In this study, weldability of bronze parts produced by powder metallurgy has been investigated by using TIG welding technique. Bronze powders were pressed into 55x44x5 mm size specimens under pressure of 350 MPa. Then these specimens were sintered at 650, 750 and 870 °C for 45 minute under argon atmosphere. Finally, the parts were welded by TIG welding method. Hardness values of the welded joints were measured and microstructural features were investigated.

The Mathematical Modeling of the Compressive Stresses on the Cutting Tool in Machining of Inconel 718

In this paper, a mathematical model has been developed for the cutting tool stresses in machining of nickel-based super alloy Inconel 718 used in aircraft and spacecraft industries, nuclear power systems and steam generators etc. necessitating oxidation and corrosion resistance, high temperature and strength. The cutting forces were measured by a series of experimental measurements and stress distributions on the cutting tool were analyzed by means of the finite element method using Ansys software. The mathematical modeling process of the compressive stresses in x, y and z directions was carried out with multiple regression analysis regarding to Ansys stress results depending on the cutting forces and the chip–tool contact area. It is found that model results had good agreement with the Ansys stress results.

The Effect of Voltage on the Arc Stud Welding of Microwave Sintered Fe+Al Powder Mixture

The joining of powder metallurgy products is of importance because of high demand in many industrial applications. In this study, the effect of welding voltage on the joint quality has been investigated using discharge arc stud welding, a low heat input welding method, without gas protection to join steel stubs to microwave sintered compacts containing a powder mixture of 26 atomic % Al and Fe (balance). It has been shown that welds with steel stubs are prone to side cracking in the weld zone and they also suffer from the oxidation of metal powders adjacent to weld zone. The forms of oxides are continuous and laminar type in welds with steel stubs and the composition of weld zone changes with increasing arc voltage.

Analysis of Functional Properties of Cu-Al2O3 Particulate Reinforced Composites. A First Assessment: Elaboration

The possibilities of Cu-Al2O3 particulate reinforced composites, of competitive functional properties, processing by the classical powder metallurgy route have been investigated taking into consideration its known technical and economical advantages in respect to the known worldwide investigated technological routes of their processing. The adopted compositions, of (5.0÷20.0) [vol.%] Al2O3, were selected in agreement with published data for a large range of applications. Pharmaceutical homogenization method applied for powder mixtures preparation proved to assure a high homogeneity, evidenced by SEM and EDS analyses. Their determined compressibility has shown that, for all compositions, the obtainable compactness is very close to that of pure Cu (even over 94 %). Cold uniaxial compaction at 500 and 700 MPa, and subsequent sintering in argon of high purity at 800 °C for 45 and 60 min have been adopted for composites realization. The performed analysis of the compacting pressure and sintering time influence on the composite compactness proved that, beside the above specified values obtaining for 700 MPa and 60 minute processing parameters, high enough values, acceptable for numerous applications, can be also obtained at 500 MPa and 60 or even 45 minutes. Finally, microstructural analysis highlighted that, by the adopted processing conditions, a high uniformity of Al2O3 particles distribution in the Cu matrix can been assured, both creating premises for obtaining good functional properties of Cu-Al2O3 composites, proving the competitiveness of the investigated PM route for their elaboration.

The Effect of Time of Powder Removal on Powder Particle Size and Shape Copper Powder Produced by Electrolysis Method

In this study, electrolyze unit, which is used for the production of metal powders, was designed and produced. The production of powder was carried out by using different parameter times of powder removal (5, 10, 20, 30 and 40 min.). The effect of time of powder removal on powder particle size and shape was examined. Laser particle measurement machine and SEM were also used to measure particle size and particle shape respectively. Experimental results indicated that an increase in time of powder removal caused an increase in powder particle size and its shape changed from acicular dentritic to globular dentritic.