Showing 5 results for M. Shamanian
M. Shamanian, M. Salehi and F. Ashrafizadeh,
Volume 16, Issue 2 (1-1998)
Abstract
The use of Fe-Al intermetallic compound coatings has been investigated in order to improve the tribological behaviour of carbon tool steel. The coatings were formed by a pack cementation process and subsequently diffusion annealing at 900˚C in an argon controlled atmosphere. The optimum diffusion time was selected on the basis of optimum thickness and tribological behaviour.
The microstructure and the phases developed on the surface were identified by metallography, microhardness, X-ray diffraction (XRD), microanalysis (EDX) and glow discharge optical spectroscopy (GDOS) techniques. Experimental results indicate that a three layer coating is formed on the surface of the aluminized specimens, the outermost layer being identified as Fe2Al5 and the underlying layers as FeAl and Fe3Al. A two layer coating was formed on the surface of the aluminized and subsequently diffusion annealed specimen at the optimum time. The FeAl and Fe3Al have been formed on and below the surface, respectively.
The results from wear testing indicate that these coatings improve the wear and frictional behaviour of carbon steel significantly. The predominant wear mechanisms of diffusion annealed specimens were identified as delamination and oxidative wear.
M. Shamanian, A. Saatchi, M. Salehi and T. H North,
Volume 21, Issue 2 (1-2003)
Abstract
The metallurgical and mechanical properties of Ti6Al4V/(WC-Co) friction welds have ben investigated. The microstructure close to the bondline comprised a mixture of acicular and equiaxed α plus β phases. The diffusion of elements in the welded specimens has been detected. The fracture strengths of Ti6Al4V/(WC-Co) friction welds markedly improved when the cobalt content in the (WC-Co) carbide substrate increased.
During the three-point bend testing of Ti6Al4V/WC-6wt.%Co welds, the crack initiated at the bondline region at the periphery of the weld and then propagated into the brittle (WC-6wt.%Co) substrate, while with the Ti6Al4V/WC-11 wt.%Co and Ti6Al4V/WC-24wt.%Co welds, the crack initiated and propagated at the bondline region.
Keywords: Friction welding, Ti6Al4V alloy, Cemented tungsten carbide, Microstructure, Fracture strength
M. Shamanian and A. Saidi,
Volume 24, Issue 1 (7-2005)
Abstract
The 25Cr-35Ni heat resistant steel has been widely used when resistance to oxidation and creep rapture at elevated temperatures is required. In this paper, the microstructural effect on the weldability of this alloy is investigated. The results of this study indicate that this steel has a perfect weldability in the as cast condition but does not possess good weldability in the aged condition. The as cast microstructure of 25Cr-35Ni steel consists of austenite matrix and a network of primary carbides, while the aged condition consists of austenite matrix and y primary and secondary carbides. The morphological change of primary
carbides and the secondary carbides precipitate formation, reducing the elongation and ductility of aged steel, should have enhanced the steel susceptibility to cracking, particularly in the area of the eutectic carbides, and hence, the reduced weldability of the steel. The cracking observed was of the intergranular type and spread along the eutectic carbides. It was found that the carbides in the as cast steel consisted of NbC and M23C6, whereas that of the aged steel also exhibited Ni16Nb6Si7 and M23C6 carbides
R. Taherian, A. Najafi Zadeh, M. Shamanian, R. Shateri,
Volume 25, Issue 1 (7-2006)
Abstract
In this study, two CCCT diagrams are drawn to be compared with a CCT diagram. The CCCT diagrams represent continuous cooling transformations in stress assisted state. The increased Md and Bd temperatures of CCCT diagrams were also compared with those of the CCT diagrams and the cause was investigated from both thermodynamic and metallurgical viewpoints. Thermodynamic examinations revealed that stress causes the mechanical driving force to increase but the total free energy of transformation to decrease hence, Md and Bd will rise. Metallurgical investigations showed that if deformation temperatures are selected in a manner to increase the structural strength of the original austenite grains prior to deformation, the shear force required for martensite and bainite transformations will arduously obtain hence, Md and Bd will fall. However, if recrystallization or full recovery occurs during or after deformation, interior grain structure softens and the shear force required for martensite and bainite transformations will readily obtain hence, Md and Bd will rise. It was also found that the nose in CCCT curves are shifted to the left as compared to that of CCT curves. This indicates that deformation of steel enhances bainite formation more readily than that of the martensite phase.
K. Sheybani, M.h. Abbasi, M. Shamanian ,
Volume 33, Issue 2 (Journal of Advanced Materials-fall 2015)
Abstract
in this research, the kinetics of carbothermic reduction of molybdenite in the presence of sodium carbonate was studied. For this purpose, mixed powder of molybdenite, graphite, and sodium carbonate with 1:4:2 mole ratio was investigated using simultaneous thermal analysis (STA) at the heating rates of 10, 15 and 20 0C /min. The results of thermal analysis were evaluated through Friedman, Kissinger, Ozawa and Coats-Redfern methods. The activation energy of reduction reaction was determined 220 kj/mole, and it was found that the reaction was chemically controlled. To study the reaction mechanism, the mixed powder was heated to 400, 800 and 1100 0C in argon atmosphere at the heating rate of 10 0C/min. X- Ray diffraction
of the reaction products and thermodynamic analysis at these temperatures indicated that carbothermic reduction of molybdenite in the presence of sodium carbonate would advance through the formation of intermediate phases, Na2MoO4 and MoO2
