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Papers by Mohamad Sadegh Amiri Kerahroodi

The purpose of current paper is production of Copper-Aluminum bimetal by using centrifugal castin... more The purpose of current paper is production of Copper-Aluminum bimetal by using centrifugal casting and evaluation of Copper-Aluminum interface and also optimization for creating metallurgical interface with appropriate and minimum discontinues between metals interface. In this research the solidification time of primary layer is calculated on base of chornief relation and second melt after different timescales that changed the interface temperature, was casted. The background structure, elements diffusion and hardness depending on the temperature of casted copper in a mold and Aluminum casting with different primary Copper bases in 100°C, 200°C, 300°C, 500°C is evaluated. The results are shown that by decreasing temperature, brittle intermetallic structures losse and hardness decrease. Two things are important for creation of complete metallurgical bonding between two metals, first the Copper temperature before Aluminum decanting and second is the lack of impurities and metal oxides...

Journal of Bio- and Tribo-Corrosion, 2021

In this study, failure analysis of a punch forming tool was studied and three types of coatings w... more In this study, failure analysis of a punch forming tool was studied and three types of coatings were applied to study their effect on the failure of the tool. The coatings were DLC, TiN and CrCN. The PECVD, PVD and TRD methods were used as coating methods. The experimental tests indicate that although there was no evidence of failure of the coated specimens, there were some microscopic defects in coatings which had some negative effects on surface quality of products. All punch forming tools were studied via FE-SEM microscope with EDS analysis. From an industrial perspective, the capital return rate of TiN coating was very high. Both DLC and chromium carbonitirde coated specimens had the same negative relative difference which means their results were worse than the uncoated specimens. The life times for the DLC, CrCN and TiN-coated specimens were respectively 1.5, 2.3 and 8 times more than that of the uncoated specimen. The roughness of specimens after 100,000 cycles were 21.021 ± 0.001, 2.024 ± 0.001, 4.031 ± 0.001 and 1.213 ± 0.001 µm for uncoated, DLC, CrCN and TiN-coated specimens, respectively. High surface hardness of the TiN coating delayed the deformation in punch forming tools and the formation of surface defects and prolonged the life time of the tool.

Journal of Failure Analysis and Prevention, 2021

Despite high level of attention in the process of making metallic fasteners, failure of the faste... more Despite high level of attention in the process of making metallic fasteners, failure of the fasteners happens in various industries. Sometimes, failures are recognized during the quality control checks in the companies. During a batch of production and during assembly test, failure of a 17-4PH stainless steel part in an exhaust fastener was seen. The aim of the present research is to figure out the reasons of the failure. The impact energy value of the intact investment casting part is 30 J, and for the failed part, it is 9.3 J. Since the impact test illustrates the bulk behavior of the parts, this decrease in the impact energy indicates a huge defect in the part. The presence of shrinkage cavities, porosities and cracks brings the weakness and failure.

Transactions of the Indian Institute of Metals, 2018

This paper presents a novel aging process consisting of two stages: an aging at 250°C for 12 h an... more This paper presents a novel aging process consisting of two stages: an aging at 250°C for 12 h and a supplementary aging at 70°C for 18 h. The ingots of Mg-5Sn and Mg-5Sn-0.5Zn alloys were solution heat-treated for 24 h at 480°C and then quenched in water. Afterward, aging treatments were performed. To compare the effects of this process on age hardening response of both alloys, other aging treatments were performed at 200°C for 60 h and at 280°C for 12 h. The age hardening responses were measured by the Vickers hardness test. The structure of specimens was investigated by XRF, DSC, XRD, and FE-SEM. Also, mechanical properties were determined by tensile test and Charpy impact test. Although by using supplementary aging process, maximum hardness of these alloys is not very different in comparison with single-as well as double-aging processes, the necessary times of aging processes are significantly lower than those at around 90%, 85%, and 50%. After the aging process, the microstructure of Mg-5Sn and Mg-5Sn-0.5Zn alloys consists of a-Mg, nano-metric particles of Mg 2 Sn, and GPzones. In Mg-5Sn alloy, after supplementary aging process, the yield strength, ultimate tensile strength, and elongation increase to 151.2 MPa, 221.2 MPa, and 8% sequentially. In Mg-5Sn-0.5Zn alloy, the YS, UTS, and elongation increase to 154 MPa, 224 MPa, and 7%, respectively. The impact energy in both alloys is 6.63 J and 7.05 J, respectively.

Oxidation of Metals, 2017

Changing the power plant boiler fuel from natural gas into fuel oil during the cold months of the... more Changing the power plant boiler fuel from natural gas into fuel oil during the cold months of the year causes hot corrosion in generating tubes. Visual observations, thickness and thermocouple measurements and ash analysis proved the hot corrosion by displaying the sticky melted ash, thickness reduction, surface temperature of tubes at about 600°C and existence of complex corrosive elements such as sodium and vanadium, respectively. Therefore, based on the experimental data from the power plant, laboratory studies were performed to survey the corrosion inhibition effect of magnesium sulfonate as an easy to use fuel additive. A low carbon steel, 70 wt%Na 2 SO 4-25 wt%V 2 O 5-5 wt%NaCl and mineral part of magnesium sulfonate ash were used as the generating tube material, corrosive and additive ashes, respectively. Two groups of specimens were coated with two different compounds of synthetic ashes, in which the first group was containing corrosive salts and the second was a calculated specific combination of mineral part of additive ash and corrosive salts. Specimens were exposed to high temperatures up to 120 h at 600°C. Power plant observations, XRF, weight loss criteria, SEM and FESEM were used to study the hot corrosion, and results were compared with similar studies. It was concluded that magnesium sulfonate could not attribute to reduce the emission of sulphurous gases. Although the first group of the specimens was highly suffered from corrosion, the other group of samples was protected against hot corrosion and the weight loss was decreased considerably. Morphology and XRD picks of corrosion products were described, and it was also concluded that Na 4 V 2 O 7 and NaV 3 O 8 compounds which are molten at 600°C were responsible for hot corrosion. The additive inhibited corrosion through formation of Na 3 VO 4 with

Engineering Failure Analysis, 2021

Abstract In this research the failure of a DIN Ck45-steelclip of a turbofan during the forming pr... more Abstract In this research the failure of a DIN Ck45-steelclip of a turbofan during the forming process was studied. As the failure was brittle and the forming was done properly, the failure was originated from a problem with raw material. The material and properties like chemical compound, hardness and tensile strength were at the proper ranges. The cold rolled steel passed the heat treatment process like spheroidize annealing and martempering prior using as clips. The problem was related to the slow rate of heating beneath of 850°C and incomplete microstructure modifying prior to spheroidizing annealing which causes the graphitization in the raw material, and brittle failure during the forming process of parts.

The purpose of current paper is production of Copper-Aluminum bimetal by using centrifugal castin... more The purpose of current paper is production of Copper-Aluminum bimetal by using centrifugal casting and evaluation of Copper-Aluminum interface and also optimization for creating metallurgical interface with appropriate and minimum discontinues between metals interface. In this research the solidification time of primary layer is calculated on base of chornief relation and second melt after different timescales that changed the interface temperature, was casted. The background structure, elements diffusion and hardness depending on the temperature of casted copper in a mold and Aluminum casting with different primary Copper bases in 100°C, 200°C, 300°C, 500°C is evaluated. The results are shown that by decreasing temperature, brittle intermetallic structures losse and hardness decrease. Two things are important for creation of complete metallurgical bonding between two metals, first the Copper temperature before Aluminum decanting and second is the lack of impurities and metal oxides...

Journal of Bio- and Tribo-Corrosion, 2021

In this study, failure analysis of a punch forming tool was studied and three types of coatings w... more In this study, failure analysis of a punch forming tool was studied and three types of coatings were applied to study their effect on the failure of the tool. The coatings were DLC, TiN and CrCN. The PECVD, PVD and TRD methods were used as coating methods. The experimental tests indicate that although there was no evidence of failure of the coated specimens, there were some microscopic defects in coatings which had some negative effects on surface quality of products. All punch forming tools were studied via FE-SEM microscope with EDS analysis. From an industrial perspective, the capital return rate of TiN coating was very high. Both DLC and chromium carbonitirde coated specimens had the same negative relative difference which means their results were worse than the uncoated specimens. The life times for the DLC, CrCN and TiN-coated specimens were respectively 1.5, 2.3 and 8 times more than that of the uncoated specimen. The roughness of specimens after 100,000 cycles were 21.021 ± 0.001, 2.024 ± 0.001, 4.031 ± 0.001 and 1.213 ± 0.001 µm for uncoated, DLC, CrCN and TiN-coated specimens, respectively. High surface hardness of the TiN coating delayed the deformation in punch forming tools and the formation of surface defects and prolonged the life time of the tool.

Journal of Failure Analysis and Prevention, 2021

Despite high level of attention in the process of making metallic fasteners, failure of the faste... more Despite high level of attention in the process of making metallic fasteners, failure of the fasteners happens in various industries. Sometimes, failures are recognized during the quality control checks in the companies. During a batch of production and during assembly test, failure of a 17-4PH stainless steel part in an exhaust fastener was seen. The aim of the present research is to figure out the reasons of the failure. The impact energy value of the intact investment casting part is 30 J, and for the failed part, it is 9.3 J. Since the impact test illustrates the bulk behavior of the parts, this decrease in the impact energy indicates a huge defect in the part. The presence of shrinkage cavities, porosities and cracks brings the weakness and failure.

Transactions of the Indian Institute of Metals, 2018

This paper presents a novel aging process consisting of two stages: an aging at 250°C for 12 h an... more This paper presents a novel aging process consisting of two stages: an aging at 250°C for 12 h and a supplementary aging at 70°C for 18 h. The ingots of Mg-5Sn and Mg-5Sn-0.5Zn alloys were solution heat-treated for 24 h at 480°C and then quenched in water. Afterward, aging treatments were performed. To compare the effects of this process on age hardening response of both alloys, other aging treatments were performed at 200°C for 60 h and at 280°C for 12 h. The age hardening responses were measured by the Vickers hardness test. The structure of specimens was investigated by XRF, DSC, XRD, and FE-SEM. Also, mechanical properties were determined by tensile test and Charpy impact test. Although by using supplementary aging process, maximum hardness of these alloys is not very different in comparison with single-as well as double-aging processes, the necessary times of aging processes are significantly lower than those at around 90%, 85%, and 50%. After the aging process, the microstructure of Mg-5Sn and Mg-5Sn-0.5Zn alloys consists of a-Mg, nano-metric particles of Mg 2 Sn, and GPzones. In Mg-5Sn alloy, after supplementary aging process, the yield strength, ultimate tensile strength, and elongation increase to 151.2 MPa, 221.2 MPa, and 8% sequentially. In Mg-5Sn-0.5Zn alloy, the YS, UTS, and elongation increase to 154 MPa, 224 MPa, and 7%, respectively. The impact energy in both alloys is 6.63 J and 7.05 J, respectively.

Oxidation of Metals, 2017

Changing the power plant boiler fuel from natural gas into fuel oil during the cold months of the... more Changing the power plant boiler fuel from natural gas into fuel oil during the cold months of the year causes hot corrosion in generating tubes. Visual observations, thickness and thermocouple measurements and ash analysis proved the hot corrosion by displaying the sticky melted ash, thickness reduction, surface temperature of tubes at about 600°C and existence of complex corrosive elements such as sodium and vanadium, respectively. Therefore, based on the experimental data from the power plant, laboratory studies were performed to survey the corrosion inhibition effect of magnesium sulfonate as an easy to use fuel additive. A low carbon steel, 70 wt%Na 2 SO 4-25 wt%V 2 O 5-5 wt%NaCl and mineral part of magnesium sulfonate ash were used as the generating tube material, corrosive and additive ashes, respectively. Two groups of specimens were coated with two different compounds of synthetic ashes, in which the first group was containing corrosive salts and the second was a calculated specific combination of mineral part of additive ash and corrosive salts. Specimens were exposed to high temperatures up to 120 h at 600°C. Power plant observations, XRF, weight loss criteria, SEM and FESEM were used to study the hot corrosion, and results were compared with similar studies. It was concluded that magnesium sulfonate could not attribute to reduce the emission of sulphurous gases. Although the first group of the specimens was highly suffered from corrosion, the other group of samples was protected against hot corrosion and the weight loss was decreased considerably. Morphology and XRD picks of corrosion products were described, and it was also concluded that Na 4 V 2 O 7 and NaV 3 O 8 compounds which are molten at 600°C were responsible for hot corrosion. The additive inhibited corrosion through formation of Na 3 VO 4 with

Engineering Failure Analysis, 2021

Abstract In this research the failure of a DIN Ck45-steelclip of a turbofan during the forming pr... more Abstract In this research the failure of a DIN Ck45-steelclip of a turbofan during the forming process was studied. As the failure was brittle and the forming was done properly, the failure was originated from a problem with raw material. The material and properties like chemical compound, hardness and tensile strength were at the proper ranges. The cold rolled steel passed the heat treatment process like spheroidize annealing and martempering prior using as clips. The problem was related to the slow rate of heating beneath of 850°C and incomplete microstructure modifying prior to spheroidizing annealing which causes the graphitization in the raw material, and brittle failure during the forming process of parts.