Papers by Keyword: Repair Welding

Abstract: This paper covers the literature review of the work by author, who have been involved in the subject of machine element repairing from the techno-economical point of view. Positive aspects of repairing, as opposed to purchasing new parts are shown and discussed. All of the examples given as part of the literature review are related to real, practical problems. It was concluded in all cases, that the repairing of damaged parts was the better option, since not only did it cost significantly less, it also noticeably decreased the equipment downtime, as there was no need to wait for the new part to be delivered.

Abstract: The ultrasonic vibratory test was carried out to evaluate the cavitation erosion/corrosion resistance of welded-deposited austenitic stainless steel/E308L-17. Three layers of the E308L-17 electrode were deposited onto AISI 1040 substrate utilizing Shielded Metal Arc Welding (SMAW) process. The eroded surfaces of the E308L welded deposit/coating and AISI 1040 substrate steel have been analyzed by evaluating surface topography, as well as scanning electron microscope (SEM) micrographs. In addition, the cumulative weight loss and erosion rate curves were attained to evaluate the cavitation resistance of the tested materials. The cavitation results showed that the E308L-17 deposited stainless steel has lost about 15 mg as a cumulative weight, while the loss of AISI 1040 substrate was about 123 mg. This is equal to 0.12% and 1.0% of the original test specimen weight for the E308L-17 and AISI 1040, respectively. Consequently, E308L-17 austenitic stainless steel can be effectively used as a protective material for surfaces exposed to cavitation wear, since the AISI 1040 substrate has been enhanced by 8 times using E308L stainless steel.

Abstract: The type IV cracking is one of the main reasons for service failure. The repair welding is implemented to solve this problem. The residual stress in P91 repair welding incorporating martensitic transformation (MT) is acquired through finite element simulation. In the simulation, the ABAQUS and the user subroutines FILM, DFLUX, HETVAL, USDFLD, UEXPAN and UHARD are adopted. The effect of MT latent heat on temperature and the effects of the volume expansion, the yield strength change and the transformation plasticity on stress are considered. The results show that there is full MT in the repair welding area and the old welding area. The MT latent heat makes the temperature of the repair welding area increase. The residual stress of the repair welding area decreases because MT relieves the thermal stress. Before repair welding, the residual stress distribution is M-shape, which is consistent with the experimental results. After repair welding, the residual stress of repair welding area decreases and the residual stress of old welding area increases.

Abstract: Two repair weld metals Inconel 52 and its newer version Inconel 52M were used as materials for development of repair welding method of a VVER 1000 pressure vessel. The properties and microstructure of the trial welds were investigated using light, scanning and transmission electron microscopy. Both modifications of Inconel revealed a structure of elongated grains with clear evidence of dendritic segregation. Fine chromium carbides occurred at wavy grain boundaries and fine cuboidal titanium carbides pinned dislocations within grains. Coarser skeletal titanium carbides and globular oxides were sparsely precipitated in interdendritic spaces. Some small common defects were observed in the weldments. No cracks were detected which could be classified as ductile dip cracking. It was concluded that both Inconel 52 and Inconel 52M are acceptable for repair welding.

Abstract: In order to produce reliable welded product quality accumulated experiments are basic requirements.But nowadays production conditions are changing and quality requirements are becoming more and more severe. In these cases using achievement of computer in hardware and software can be a nice tool for improving welding production in efficiency and time saving. In this study three samples are shown in order to show the improvement in welding products with the aid of computer. (Repair welding, Tack welding and High frequency electric resistance welding)

Abstract: Maraging steels are a special class of ultrahigh-strength steels which presents a combination of high mechanical strength, excellent toughness, high temperature strength and corrosion resistance. The joint of sheets/plates by welding processes are fundamental for aeronautical and industrial products in addition Brazil has been developing technologies in welding ultrahigh-strength steels such as AISI 4340ESR and SAE 300M steels for its domestic space launch program and has currently decided for the replacement of these steels by Maraging 300 steel in some projects. In this work, we studied the welding process of the Maraging 300 steel for two different routes: Tungsten Inert Gas (TIG or GTAW) and Plasma Arc Welding (PAW). Filler additions were used for both processes. Procedure after any welding demands non destructive testing and sometimes non approved defects considering the usage of the product require for welding repair. Verification of the effects of this operation was made through a simulation of a welding repair for both types of welding. Specimens were submitted to heat treatment consisting of a solution annealing and aging and their microstructures were examined. The microhardness measurements were made on samples with and without repair characterized the fusion and heat affected zones. Specimens were submitted to tensile testing and the fractured surfaces were examined by a scanning electron microscope. Results of microstructure exam revealed the presence of austenite (γ) in FZ (Fusion Zone). After the welding repair simulation, a new different colored zone appeared in the HAZ (Heat Affected Zone) for both processes due to reheating of the sheet provided by the repair process. In the HAZ near FZ an important grain growth due to the heating occurred. Also, close FZ that was submitted to new heating due to repair it was noted an apparent growing of grain size relative to original grain size. The microhardness measurements showed that there is a reduction in hardness in the FZ and the region immediately (fusion line) compared to base material values. After the aging heat treatment a recovery of hardness values took place in these regions but the values themselves remain smaller than the base material. It was observed an increase of values of the microhardness in dark regions in the HAZ provoked by a phenomenon of aging locally due to the dissipation of the heat of the welding process and posterior repair. After aging, those differences disappeared. It was observed that there was not a large difference between the yield and strength limits considering both processes of welding, as well as between both situations after repair. It could be seen that the rupture began in the region near FZ and followed in the direction of the weld bead. The analysis of the fracture surfaces showed that this happened by ductile way, forming dimples.

Abstract: Microstructural analysis and microhardness measurement of experimental repair weld joints were carried out in heat affected zone (HAZ) of the base material (BM) – steel 15Ch2NMFA after weld deposition of several layers by welding metal of Inconel FM 52. A temper bead welding (TBW) technique was used. Required microhardness up to 350 HV0.1 in heat affected zone of base material in distance 0.5 mm from fusion line was exceeded in all three experimental blocks with various welding energy inputs during deposition of three or five weld layers. Metallography showed reaustenitization and structure transformation in HAZ after the deposit of first layer in all three blocks. After deposit of the last layer the structure of HAZ in two blocks was tempered only and one variant of them have been recommended for futher technological tests. Structure of HAZ of the third block was not full tempered even after the last layer deposit.

Abstract: The casting disfigurement on the upper end-face of cast iron roller ring is easy to happen. The paper analyses the method of disfigurement repairing. The disfigurement of centrifugal foundry cast iron roller ring has been eliminated by strict processing technology. Rate of finished products of the cast iron roller ring is improved by repair welding as a result.

Abstract: Since the oil price has been significantly jumped for recent some years, the diesel engine of the merchant ship has been mainly used the heavy oil of low quality. Thus, it has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of a combustion chamber is getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the enginet parts surrounded with combustion chamber is more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these parts is very important to prolong their lifetime in a economical point of view. In this study, Inconel 718 filler metal were welded with GTAW method in the cast steel which would be generally used with piston crown material. In this case, the mechanical and corrosion properties between weld metal zone (WM) welded to the groove which were artificially made in the base metal and deposited metal zone (DM) only welded on the surface of the base metal by Inconel 718 filler metal were investigated using electrochemical methods, such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% H₂SO₄ solution. The deposited metal zone exhibited a lower value of hardness compared to the weld metal zone. Moreover, the corrosion current density also indicated significantly a lower value in the deposited metal zone compared to the weld metal zone, showing a nobler corrosion potential than the weld metal zone. The corrosive products was not observed both in the weld and deposited metal zones. The microstructure of the pearlite with black color was hardly observed in the weld metal zone, while, the microstructure of ferrite with white color indicated nearly mostly in the weld metal zone. However, ferrite microstructure considerably appeared in the deposited metal zone with crystal pattern, and pearlite microstructure was more or less observed in the deposited metal zone. In particular, the polarization characteristics such as impedance, polarization curve and cyclic voltammogram associated with corrosion resistance property were well in good agreement with each other.

Abstract: Since the oil price has been significantly jumped for recent some years, the diesel engine of the merchant ship has been mainly used the heavy oil of low quality. Thus, it has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of a combustion chamber is getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the most parts surrounded with combustion chamber is more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these parts is very important to prolong their lifetime in a economical point of view. In this study, Inconel 718 filler metal was welded with GTAW method in the cast steel which would be generally used with piston crown material. And the corrosion properties of weld metal zone, heat affected zone and base metal zone were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% H₂SO₄ solution. The weld metal and base metal zones exhibited the highest and lowest values of hardness respectively. Furthermore, the corrosion current density of the weld metal zone indicated the lowest value, having the highest value of hardness. The corrosive products with red color was more or less observed in the base metal zone, while the weld metal zone exhibited the general corrosion without corrosive products of red color. The microstructure of the pearlite with black color was predominantly observed in the base metal zone, however, the microstructure of ferrite with white color increased increasingly in the heat affected zone, and the microstructure of ferrite with white color was significantly observed in the weld metal zone. In particular, the polarization characteristics such as impedance, polarization curve and cyclic voltammogran associated with corrosion resistance property were well in good agreement with each other. Keywords : Repair welding, Inconel 718 filler metal, GTAW, Weld metal zone, Electrochemical method, Corrosion current density, Hardness. Microstructure