November 2020 Volume 2

the desired temperature was reached, 6 samples were placed in a basket and immersed into the solution for 30 minutes. This process was repeated for all samples. Figure 3 highlights this procedure with a comparison of samples before and after Nickel plating. FORGING RESEARCH AND TECHNOLOGY

deformation samples wer temperature 1°C/min (3) (1). To obs prior to tra each alloy w and (b) after

All the dilatometry tests were done using a LINSEIS L78 Machine coupled with an induction furnace. The temperature range of the system is between -150C to 1600C, with heating rates up to 4000K/s and cooling rates up to 4000K/s, approximately. After the dilatometry tests, the samples were subjected to microstructural analysis. 2.3 Hot Compression The samples used in this part of the study have been sectioned from the two 4340 steel plates. Cylindrical samples were machined with a height-to-diameter ratio of 1.5. Their dimensions are of 19.05mm height and 12.4mm diameter, as shown in Figure 2. The samples have a small diameter hole at the mid-eight where a thermocouple is attached. In addition, the top and bottom of the sample a small reservoir was machined. This geometry allows the application of a special lubricant to reduce barreling during hot deformation testing. A total of 12 compression samples were machine from each steel. the dilatometry tests, the samples were subjected to microstructural analysis. 2.3. Hot Compression The samples used in this part of th st dy have been sectioned from the two 4340 steel plates. Cylindrical samples were machined with a height-to-diameter ratio of 1.5. Their dimensions are of 19.05mm height and 12.4mm diameter, as shown in Figure 2. The sa ples have a small diameter hole at the mid-eight where a thermocouple is attached. In addit on, the op and bottom of the sample a small reservoir was machined. This geo etry allows the application of a special lubricant to reduce barreling during hot deformation testing. A total of 12 compression samples were machine from each steel. Figure 2: Schematic of the compression sample. Prior to hot compression testing the samples were protected against oxidation. This process includes the following steps: 1) removal of oxides, using a pickling solution, and 2) Nickel plating. The pickling solution contained 100mL of hydrochloric acid and 100mL of deionized water (Pickling - 50% HCl and 50% H2O). All of the samples were immersed for approximately 5 minutes. The Nickel plating consisted of immersing the samples in Nickel solution containing 18.25mL of Electroless Nickel (Part A), 56.75mL of Electroless Nickel/Cobalt (Part B) and 300mL of deionized water (1 Part A + 3 Part B + 16.44 Part H2O – in volume). To activate the mixing process, the solution was heated on a hot plate to 90°C, also the temperature at which coating occurs. Once the desired temperature was reached, 6 samples were placed in a basket and immersed into the solution for 30 minutes. This process was repeated for all samples. Figure 3 highlights this procedure with a comparison of samples before and after Nickel plating. Figure 2: Schematic of the compression sample. Pr r to hot compression testing the samples were protected against oxidation. This process includes the following steps: 1) removal of oxides, using a pickling solution, and 2) Nickel plating. The pickling solution contained 100mL of hydrochloric acid and 100mL of deionized water (Pickling - 50% HCl and 50% H2O). All of the sa ples were immersed for ap ximat ly 5 minutes. The Nickel plating consisted of immersi the samples in Nickel solution containing 18.25mL of Electroless Nickel (Part A), 56.75mL of Electroless Nickel/Cobalt (Part B) and 300mL of deionized water (1 Part A + 3 Part B + 16.44 Part H2O – in volume). To activate the mixing process, the solution was heated on a hot plate to 90°C, also the temperature at which coating occurs. Once the desired temperature was reached, 6 samples were placed in a basket and immers d nto the solution for 30 minutes. This process was repeat d f r all samples. Figure 3 h ghligh s this procedure with a comparison of samples before and after Nickel plating.

ies were rom the nditions. Argon Samples n were 0C, and uenched prepared hniques e Prior studies received ximately ngth. A ight (8) Wrought o 900C soaking cooling. d using min (9), min (6), min (3), s shown

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FORGING RESEARCH

Figure 3: (A) Nickel Plating procedure, (B) before Ni plating, and (C) after Ni plating. Once the samples have been Ni plated they are ready for hot compression testing. The tests were done using the guidance of industrial partners, with a strain rate of 0.25; a single hit of 50% deformation after 2 minutes of holding time at 900C. Figure 4 shows a schematic thermomechanical cycle for the hot compression testing performed. The specimens were reheated to the same temperature used for the dilatometric studies. Then, the compression samples were deformed 50% in one hit using a computer controlled high temperature deformation system. After deformation the samples were immediately cooled to room temperature at three different cooling rates, 1°C/min (3), 20°C/min (2) and 100°C/min (1). To observe the state of the austenite prior to transformation, two samples for each alloy were water quenched (a) before and (b) after deformation. ( C ) Figure 3: ( A ) Nickel Plating procedure, ( B ) before Ni plating, and ( C ) after Ni plating. Once the samples have been Ni plated they are ready for hot compression testing. The tests were done using the guidance of industrial partners, with a strain rate of 0.25; a single hit of 50% d formation after 2 minutes of h lding time at 900C. Figu e 4 shows a schematic thermomechanical cycle for the hot compression testing performed. The specimens were reh ated to the same tem rature used for the dilatometric stud es. Then, the compression samples were deformed 50% in one hit using a computer controlled high temperature deformation system. After deformation the samples were immediately cooled to room temperature at three different cooling rates, 1°C/min (3), 20°C/mi (2) and 100°C/min (1). To observe the s ate of the stenite prior to transformation, two samples for each alloy were water quenched (a) before and (b) after deformation. ( B )

etry tests. using a with an range of 0C, with cooling y. After

Figure 4: Schematic of the Thermomechanical Processing. Figure 4: Schematic of the Thermomechanical Processing.

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FIA MAGAZINE | NOVEMBER 2020 85 The tests were performed using an INSTRON Universal Testing Machine adapted with an infrared furnace. To minimize oxidation during testing, all of the

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