In this research, the production and properties of expander sliding bearings of Ahwaz Pipe Mills (APM) company were studied. In order to produce the sliding bearing, lining of phosphor Bronze alloy (Cu-7.5Sn) on the steel substrate was conducted by shielded metal arc welding (SMAW), oxy fuel brazing, and compound casting processes. In cladding by SMAW method, the effect of heat input and the number of welding passes were also analyzed. The microstructure of created clad layers and the joint interfaces were analyzed by optical and scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). Finally, the mechanical properties and wear behavior of the clad layers were analyzed by hardness, microhardness, and wear tests. Analyzing the microstructure of the clad layers showed that in all created clads, after solidification, a two-phase microstructure is formed. This two-phase microstructure includes α phase in the center of dendrite and eutectoid α+δ which is formed around the dendritic arms. In the clad layers that formed by SMAW process, due to dillution effect of the substrate resulted from high temperature of the arc, the Fe4Cu3 intermetallic compound is formed in addition to the above phases. The presence of this intermetallic was not observed in the clad layers produced by brazing and compound casting processes. For the clad layers created with SMAW process, the volume fraction of the intermetallic compounds is increased by increasing the heat input. This occurs as a consequence of increasing the dilution effect of the steel substrate. On the other hand, with increasing the number of welding passes, due to decreasing the dilution effect of the substare, formation of Fe4Cu3 intermetallic compounds decrease.
By hardness analyzing of the clad layers, it is observed that the layers created by compound casting and brazing processes, have the lowest hardness. That is while for the samples claded by SMAW process, as a consequence of formation very hard intermetallic compounds (Fe4Cu3), the hardness was higher than the other clad layers. In the wear testing, the lowest wear rate was for the clad layers made by SMAW process and the best wear properties were achieved in multi-passes clad layers.

In this research, different locations of an IN-738 superalloy gas turbine blade, operated for long-term services (100,000 hours) were investigated. The microstructure of the service-exposed turbine blade showed significant changes in gamma prime precipitates morphology and grain boundary carbides in compare with an as-new blade. The changes in microstructure were not the same at different locations of the turbine blade and the areas with higher temperatures service conditions showed more microstructural changes. Several rejuvenation heat treatments were conducted in order to recover the microstructure and properties of the service-exposed turbine blades. Microstructural evolution by OM and FESEM showed that among all rejuvenation heat treatment cycles investigated, solution treatment at 1175ºC/3h/AC (air cooling) followed by two-stage aging treatments at 925ºC/1h and 845˚C/24h was more successful to relatively revert the microstructure back to its virgin state. The recovered morphology of gamma prime precipitates after rejuvenation treatment, caused the rejuvenated samples to have a hardness close to as-new blade. The results of impact tests on service-exposed and rejuvenated samples showed that the rejuvenation heat treatment was not led to formation of harmful TCP phases and any reduction in impact energy of the turbine blades. Both of the service-exposed and rejuvenated blades were subjected to cyclic hot corrosion tests to evaluate the resistance to hot corrosion. Microscopic studies, phase characterizations and weight changes results, showed that the rejuvenation treatment was led to an increase in resistance to hot corrosion for service-exposed blades. After the rejuvenation treatment, due to dissolution of continuous grain boundary carbide films, the distributions of the protective elements (like chromium) in the matrix of the alloy were improved. This issue led to better formation of the protective layer on surface of the alloy and then more resistance to hot corrosion of the rejuvenated samples.

Due to the high level of nickel and chromium in chemical composition, the AISI 310 austenitic stainless steel is one of the most common alloys for application in high temperature and oxidative conditions. On the other hand, high strength low alloy (HSLA) steels are another group of carbon steels which achieve their excellent strength and mechanical properties by adding only a few percent of alloying elements such as Ti, V and Nb. Existing low amount of carbon content in the chemical composition, causes the HSLA steels to have good weldability. Lower price than high alloy stainless steels and in point of view of economic consideration, substituation of stainless steel with HSLA steels is very favourable for different industries. In this way, dissimilar joining of these steels seems to be inevitable. Generally, the selection of a suitable filler metal in dissimilar welding is one of the most important concerns. In recent years, extensive investigations have been conducted for introducing suitable filler materials in dissimilar welding processes. In dissimilar welding, filler metal must be easily alloyed with the base metals to develop a suitable weld metal in different service condition. In present work, welding of an austenitic stainless steel (AISI 310) and a ferritic low alloy steel (API 5L X60) were conducted by tungsten inert gas (TIG) welding process using four different filler metals, namely ERNiCr-3, ER2209, ER309L, and ER310. Microstructure characteristics and mechanical properties of the weldments were studied using optical and scanning electron microscopy, ferrite-scope, hardness, tensile and impact tests. To evaluate the effect of heat input on the microstructure and mechanical properties of these joints, the welding of the samples were conducted in three different heat inputs 1.12, 1.22 and 1.4 kJ/mm. The results showed that all of the four filler metals can be used for dissimilar joining of AISI 310/API 5L X60 steels. However the use of ER 2209 duplex stainless steel filler metal, gives better mechanical properties than other filler metals. On the other hand, it was found that, increasing the heat input while using ER2209 filler metal, causes an increase in fracture energy and also a small decrease in hardness of the weldments.