An evaluation of the macro damage on metal matrix composites after high velocity impact

The ballistic impact failures and damages on metal matrix composites reinforced by SiC and alumina are studied. AA 6063 aluminum alloy is reinforced with SiC and alumina particles in different sizes and percentages by casting method. Ballistic tests are carried out by two different projectile types, AP (armor piercing) 7.62 and 9 mm. The macrography of the craters and holes created by high velocity projectiles impact are analyzed by light and scanning electron microscopy studies. The projectile type strongly influences the damage formation. When the high velocity projectile (AP 7.62, 7.9g, 710 m/s) impacts the 30% SiC or Al2O3 reinforced composite, it leads to deep craters and then a hole by passing the thickness of the composite target thoroughly. Brittle cracking on the target and on the reinforcing particles are also observed after impact. If this impacting carried out on the composite is relatively tough (i.e., having 15% SiC), swelling and petalling on the entrance and back sides of the hole are also created without any cracking or breaking. In case of impacting by a lower velocity projectile (9 mm, 7.47 g, 400 m/s) on the 15% SiC composite target, it can pass the thickness with or without its jacket. This projectile cannot pass the composites reinforced by 30% SiC and Al2O3. Besides some damages such as plastic deformation and craters occur on the projectile tip

EVALUATIONS ON THE FRICTION AND WEAR BEHAVIOUR OF SOME STEEL AND MM COMPOSITE SURFACES AT ELEVATED TEMPERATURES

The properties of machine elements must be suitable for their working conditions because they may be subjected to heavy working conditions such as resistant to fatique, wear, corrosion and high temperature during the service life. Their microstructure and surface properties have to support the requirements for these conditions. For these reasons, the microstructure and surface properties of the components to be worked at high temperature should be improved by suitable treatment methods such as PVD coating, surface alloying or coating and thermochemical heat treatments, etc

TRIBOLOGICAL BEHAVIOR OF PLASMA NITRIDED-722M24 MATERIAL UNDER DRY SLIDING CONDITIONS

The tribological behaviour of plasma nitrided 722M24 was evaluated under dry sliding conditions. The plasma nitrided samples were fully characterized, using metallographic, X-ray diffraction and microhardness techniques, before wear testing. Wear tests were performed on a "Universal" wear testing machine developed by NCT with plasma nitrided AMS 6472 used as the counterface material. The resulting wear loss was monitored as a function of load and test time. Although all the nitriding treatments improved the wear characteristics of the 722M24 material, the level of improvement was related to the temperature and duration of the nitriding treatment. There are specific combinations of case depth and surface hardness which are required to ensure minimum wear loss. Plasma nitriding for 9 h at 550-degrees-C and for 16 h at 570-degrees-C produced the best results in terms of preventing weight loss. Surface hardness is more important than case depth in preventing wear loss. However, a certain thickness of case is necessary to support the hard surface layer. Long treatment times produce lower surface hardnesses and deeper cases which are less effective in preventing wear

WEAR CHARACTERISTICS OF TIO2 COATING AND SILICON-CARBIDE ALLOYED LAYER ON TI-6AL-4V MATERIAL

Wear properties of Ti-6Al-4V material (IMI-318) TiO2 coated and electron beam alloyed with silicon carbide were tested. Thickness of oxide coating, alloying conditions and properties of the alloyed layer such as hardness, layer thickness and microstructure are described. Wear tests were carried out on a general-purpose wear machine by using a disc-disc sample configuration under lubricated conditions. Counterface materials to oxide-coated and to surface-alloyed specimens were plasma-nitrided AISI 51100 and hardened AISI 4140 steels respectively. The resulting weight loss and wear resistance were monitored as a function of sliding distance and applied load. Although the electron beam alloying improved the wear resistance of Ti-6Al-4V material, the oxide coatings on the material were not resistant to wear

Tribology at high-velocity impact

The tribological events taking place when a high-velocity projectile hits a SiC particulate reinforced AA 5083 composite material was examined under real conditions. The samples were cast in a disc shape by squeeze casting method. Different volume fractions of SiC particles were used. They were solidified under 180 MPa in a steel mould with a 650-700 degrees C temperature range. SiC particles with the size of 250-500 mu m, and 30% and 45% in volume fraction were incorporated into the matrix material. The composites were machined to ensure a smooth surface and to obtain samples without burrs. The samples had a diameter and thickness of 140 and 20 mm, respectively. The terminal ballistic tests were carried out in an army zone under standard test conditions. An AP 7.62 mm armour piercing projectile with a speed of 710m/s was used for testing the composite

WEAR PROPERTIES OF STEEL PLASMA-NITRIDED AT HIGH-TEMPERATURES

The wear behaviour of 722M24 (En40B) steel plasma nitrided at high temperatures for long durations was investigated. Under dry sliding and abrasive-containing lubricated conditions, the wear characteristics of the steel were studied as a function of load, time and white layer thickness. The white layer and the wear debris were characterized by X-ray diffraction. The topography of the wear surface was examined in a scanning electron microscope. The plasma nitriding process was carried out using a 20 kW plasma processing unit in cracked ammonia atmosphere. Treatment times of up to 100 h were employed with temperatures of 550, 570 and 590-degrees-C. Wear tests were performed with plasma nitrided AMS 6472 as the counterface material. The tests under abrasive-containing lubricated conditions were carried out with 10% carborundum powder 10 mum in size in SAE-30 machine oil. The wear resistance of the steel was improved by plasma nitriding and the abrasive wear resistance of nitrided steel was higher than the wear resistance under dry sliding conditions. However, the surface hardness and white layer thickness are very important factors in the wear behaviour of steel

AN INVESTIGATION OF THE PROPERTIES AND WEAR BEHAVIOR OF PLASMA-NITRIDED HOT-WORKING STEEL (H13)

The microstructural properties and wear behaviour of AISI H13 steel which had been plasma nitrided at 530 and 550-degrees-C for times between 4 and 100 h have been investigated. The effect of treatment temperature and time on the microstructure have been examined. The wear behaviour of material treated for 4 and 100 h has also been observed. It was seen that a total case depth of 0.55 mm with a hardness of 1000 HV can be achieved in 100 h. However, the white layer thickness is increased to 17-mu-m while the core hardness is reduced to 480 HV at 550-degrees-C. The wear rate of the sample treated at 550-degrees-C for 100 h is higher than that of the sample treated at 550-degrees-C for 4 h

An evaluation of the using possibilities of the carbonitrided simple steels instead of carburized low alloy steels (wear properties)

In this study, the wear behaviour of carburized and carbonitrided AISI 1020 and 5115 steels, widely used in industry, were investigated. The surface properties, microstructures, hardness distributions and wear behaviour of the treated steels were determined as well as the wear characteristics and weight losses of the treated samples as a function of wear test durations and loads. The results indicated that the surface of carbonitrided steel have epsilon-carbonitride compound layer and diffusion zone with chromium iron carbide (Cr, Fe)(7)C-3, chromium carbide nitride (Cr(6)2C(3) . 5N(0.3)), chromium nitride (Cr2N), [Cr, Fe(2N(1...x))] and Fe2N phases. The surface hardness and wear resistance of the carbonitrided samples are higher than those of the carburized samples. The carbonitrided 5115 steel has the highest wear resistance followed by carburized 5115, carbonitrided 1020 and carburized 1020 respectively. (C) 1997 Elsevier Science B.V

EXPERIMENTAL-STUDY OF THE ABRASIVE WEAR BEHAVIOR OF PLASMA-NITRIDED GEARING STEEL

An increase in the wear resistance of AISI 722M24 steel can be achieved by the use of plasma nitriding, which produces a hard surface layer on the steel. The wear test in this investigation uses 10% carborundum powder in SAE-30 oil and emery paper with different grit sizes as the abrasive media. The plasma-nitrided samples were fully characterized using metallographic, X-ray diffraction and microhardness techniques before wear testing. Testing was carried out on a compact laboratory rig, over ranges of test loads and times. Plasma-nitrided AMS 6472 steel was used as the counterface material, with lubricated abrasive conditions. The tests carried out with the emery papers were performed by rubbing specimens against the different emery papers on a grinding wheel. The worn surfaces were examined using scanning electron microscopy. The test results show that the surface hardness and compound layer thickness are more important than the case depth in preventing weight loss. Also, the operating speed and abrasive grit size have an important effect on the mass loss of the plasma-nitrided steel

The effects of homogenization and recrystallization heat treatments on low-grade cold deformation properties of AA 6063 aluminum alloy

In this study, the effect of cooling rate during homogenization treatment of AA 6063 aluminum alloy on the low-grade cold deformation-recrystallization properties has been investigated. For this purpose tapered tensile test specimens (one side 10 mm width and the other side 18 mm) were prepared from the material taken from billet produced by semi-continuous casting method. These specimens were homogenized at 560 degrees C for 6 h and cooled down at five different rates. Each group has three specimens. These specimens were then tensile tested to obtain deformation gradient and annealed at 450 degrees C, 500 degrees C, and 550 degrees C for 1 h. Following these treatments specimens were subjected to metallographic examination