106122_Brochure_X15TN RA 820 Brochure X15TN
User Manual: RA-820
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X15TN TM X40CrMoVN16-2 A high hardness, corrosion and fatigue resistance martensitic grade CONTINUOUS METALLURGICAL INNOVATION SPECIAL STEELS DEVELOPMENT RESEARCH SERVICE Enhancing your performance X15TN X40CrMoVN16-2 THE INDUSTRIAL ENVIRONMENT Numerous applications require the use of stainless steel resisting high mechanical stresses and abrasive or corrosive environments. For fuel injection systems, pollution control devices, tools used for medical applications or knives, the required hardness often exceeds 55 or even 58 HRC. The choice of stainless grades then becomes quite limited. Starting from the high alloyed martensitic steels down to precipitation hardening stainless steels, hardness and abrasion resistance decrease while corrosion resistance increases. A very common grade used is AISI 440C / X105CrMo17, and the associated compositions with slight variations of carbon, chromium or molybdenum. Addition of other elements like tungsten, vanadium and niobium can be made in order to improve the temperature resistance. However, for all these grades, it is the carbon content that gives the required hardness and it has to be kept at a minimum of 0.7% to yield 58 HRC. Such high carbon content has the following consequences: • Coarse carbide structures • Localized Cr depletion around large carbides • High sensitivity to tempering temperature due to carbide precipitation … Leading to well-documented limitations: • Limited corrosion resistance • Very limited corrosion resistance at high tempering temperatures • Limited fatigue resistance • Sensitivity to carbide pull-out • Polishing difficulties DEVELOPMENT OF X15TN The following criteria have been taken into account during the design of this grade, initially developed for aerospace bearings and induction hardened ball-screws: • High fracture toughness combined with high hardness, typically 58 HRC. • Low retained austenite compared to AISI 440C after heat treatment in order to ensure a high dimensional stability of the parts. UNS: S42025 Euro Number: 1.4123 2 X15TN X40CrMoVN16-2 CHARACTERISTICS OF THE GRADE • Partial substitution of carbon with nitrogen. For steels containing 13-17 % of Cr, the addition of nitrogen through a conventional melting method allows a saturation content of ca 0.20 %. In combination with 0.4% to 0.5% carbon: > A minimum hardness of 55 or 58 HRC can be ensured, > A microstructure of fine eutectic carbides is obtained. • Nitrogen combined with chromium and molybdenum plays a favorable role in pitting corrosion resistance. • Molybdenum and vanadium ensure a secondary hardening. These elements replace chromium in the precipitates. The chromium content in the matrix is kept at a high level, therefore contributing to an improved corrosion resistance, even when tempering at high temperature. APPLICATIONS • Fuel injection, pollution control systems in abrasive / corrosive environments (biofuels, combustion gases) • Cutting blades with high requirements on corrosion resistance • Surgical instruments • Mold components for synthetic material processing • Glassware molds CHEMICAL COMPOSITION C Si Mn Cr Mo V N Ni min. 0.37 - - 15.00 1.50 0.20 0.16 - max. 0.45 0.60 0.60 16.50 1.90 0.40 0.25 0.30 SPECIFICATIONS • X40CrMoVN16-2 • UNS: S42025 • Euro Number: 1.4123 UNS: S42025 Euro Number: 1.4123 3 X15TN X40CrMoVN16-2 CCT DIAGRAM Austenitization : 1075 °C / 1967 °F - 30 min °C °F 1832 1000 Austenite 1652 900 800 1472 - Grain-boundaries carbide 700 1292 - Ferrite - Pearlite - Troostite 600 1112 500 932 400 752 300 572 200 392 Bainite + Martensite Martensite - Austenite 100 HV 50 = 517 543 550 568 610 0 1 Sec. 100 10 1 min 1000 648 661 644 579 406 10000 100000 212 32 15 min 1 hr 2 min 4 hr 2 hr 24 hr 8 hr Transformation Points 1050 °C 1075 °C Ac1 850 / 870 °C Ac3 890 / 900 °C Ms 120 / 130 °C 80 / 100 °C Mf - 50 / - 60 °C - 80 / - 100 °C UNS: S42025 Euro Number: 1.4123 4 X15TN X40CrMoVN16-2 MACROSTRUCTURE The segregation observed in the ingots is well within the limits of the aerospace industry requirements: Class Type Severity 1 2 3 4 Freckles White spots Radial segregation Ring pattern A A B B Macrostructure according to ASTM A 604 CLEANLINESS The typical values in terms of cleanliness are better than the usual requirements for such a grade. Typical values according to ASTM E45 A B C D Thin Thick Thin Thick Thin Thick Thin Thick 0 0 ≤1 0 0 0 1 0.5 Typical Values according to DIN 50602 K1 ≤ 3 UNS: S42025 Euro Number: 1.4123 5 X15TN X40CrMoVN16-2 MICROGRAPHIC CHARACTERIZATION Annealed Condition The observation of the annealed structure shows a good coalescence of the carbides. X15TN x 100 x 500 Heat Treated Condition Compared to X105CrMo17 (AISI 440C) the carbides are small (3 - 4 µm to 10 µm depending on the section) and well distributed within the matrix. The coarsest carbides are roughly 20 to 30 µm. Typical Aspect of the carbides X15TN x 200 UNS: S42025 Euro Number: 1.4123 6 X105CrMo17 X15TN X40CrMoVN16-2 Typical Structure of grades X15TN and X105CrMo17 in the used condition X15TN X105CrMo17 x 100 MECHANICAL CHARACTERISTICS Annealed Condition Annealing cycle: 860 °C / 8 h slow cooling to 550 °C / Air In the annealed condition the hardness is approximately 250 HB. Typical tensile test results on a 22 mm diameter bar are as follows: UTS (MPa) 0.2% YS (MPa) El (%) RA (%) 820 550 16 45 UNS: S42025 Euro Number: 1.4123 7 X15TN X40CrMoVN16-2 Heat Treated Condition The heat treatment conditions are optimized in order to obtain simultaneously: • Hardness ≥ 58 HRC • Retained Austenite ≤ 10 % The following graphs show the influence of the heat treatment conditions on hardness and retained austenite content. 61 Hardness HRC 60 59 Tempering 180 °C 58 Tempering 525 °C Double tempering 525 °C 57 56 55 1050 1075 1100 Austenitizing temperature °C 30 Residual austenite % 25 20 Tempering 180 °C 15 Tempering 525 °C Double tempering 525 °C 10 5 0 1050 1075 Austenitizing temperature °C UNS: S42025 Euro Number: 1.4123 8 1100 X15TN X40CrMoVN16-2 For low tempering temperatures (180°C), the retained austenite content increases with the austenitizing temperature ( ret = 25% at 1100°C) and hardness decreases accordingly. For high tempering temperatures (525 °C): • A progressive increase of the retained austenite content with the austenitizing temperature. • A major influence of the double tempering on the retained austenite content. • An increase of hardness with the austenitizing temperature up to a certain limit, followed by a drop due to an increasing content of retained austenite. The hardness spread for austenitizing temperatures between 980 °C and 1080 °C is shown below: 200 400 600 800 1000 200 300 400 500 1200 °F 600 °C HRC 60 58 56 54 52 50 48 100 Based on these results, optimized heat treatment conditions are presented in the following tables and graphs. UNS: S42025 Euro Number: 1.4123 9 X15TN X40CrMoVN16-2 Heat treatment for optimized hardness and corrosion resistance. °C / °F 1050 °C / 1922 °F 600 °C Gas or Oil Cooling 1100 °F 180 °C / 360 °F RT Time -80 °C / -112 °F HRC 59 HV 685 Austenite 9% UTS 2320 MPa - 336 ksi 0.2 % YS 1825 MPa - 265 ksi E 4% RA 10% Charpy V 10 J - 7.5 ft.lb K1c 14 MPa√m - 12.7 Ksi√in 7 Endurance limit 10 cycles (Rotative bending) UNS: S42025 Euro Number: 1.4123 10 928 MPa - 135 Ksi X15TN X40CrMoVN16-2 Heat treatment recommended for a good corrosion resistance and increased toughness. °C / °F 1010 °C / 1850 °F Gas or Oil Cooling 180 °C / 360 °F RT Time HRC 56.5 HV 630 Austenite 9% UTS 2160 MPa - 313 ksi 0.2 % YS 1610 MPa - 233 ksi E 4% RA 12 % Charpy V 20 J - 7.5 ft.lb K1c 16.5 MPa√m - 18.2 Ksi√in 7 Endurance limit 10 cycles (Rotative bending) 865 MPa - 125 Ksi UNS: S42025 Euro Number: 1.4123 11 X15TN X40CrMoVN16-2 Heat treatment cycle optimized for high working temperatures, high hardness and moderate corrosion resistance. °C / °F 1075 °C / 1967 °F Gas or Oil Cooling 500 °C / 932 °F 600 °C 500 °C / 932 °F 1100 °F RT Time -80 °C / -112 °F HRC 59.5 HV 700 Austenite 12 % UTS 2350 MPa - 340 ksi 0.2 % YS 1580 MPa - 229 ksi E 4% RA 10 % Charpy V 5.5 J - 4.5 ft.lb K1c 16 MPa√m - 14.6 Ksi√in Endurance limit 107 cycles (Rotative bending) 954 MPa - 138 Ksi UNS: S42025 Euro Number: 1.4123 12 X15TN X40CrMoVN16-2 Recommended heat treatment cycle for subsequent surface induction hardening. The tempering temperature can be adapted to the required core hardness. °C / °F 1050 °C / 1922 °F Gas or Oil Cooling 650 °C / 1202 °F 600 °C 650 °C / 1202 °F 1100 °F RT Time HRC 36 Austenite 12 % UTS 1200 MPa - 174 ksi 0.2 % YS 900 MPa - 131 ksi E 12 % RA 40 % Charpy V 10 J - 7.5 ft.lb K1c 66 MPa√m - 60 Ksi√in Endurance limit 107 cycles (Rotative bending) 640 MPa - 131 Ksi UNS: S42025 Euro Number: 1.4123 13 X15TN X40CrMoVN16-2 CORROSION RESISTANCE The corrosion resistance is characterized below with two different tests: • Salt spray test according to NF X 41-002 • Electrochemical test (potentiocinetic) - H2SO4 – 1% - de-aerated solution Salt spray test The results are presented with a normalized scale based on how much surface area of the test piece has been oxyded. 10 X15TN - 1050 °C / - 80 °C / 180 °C 9 X15TN - 1075 °C / - 80 °C / 2 x 500 °C Corrosion scale 8 X105CrMo17 - 1050 °C / - 80 °C / 180 °C 7 6 5 4 3 2 1 0 24 hrs 96 hrs 264 hrs Exposure time These results show the benefit of low temperature tempering in terms of corrosion resistance compared to higher tempering conditions. The decrease in corrosion resistance for the higher tempering temperature is due to the formation of secondary carbides, which consume part of the chromium. The matrix is therefore less rich in chromium and less resistant to corrosion. As shown in the pictures below, corrosion resistance is significantly improved when compared to the standard solution X105CrMo17 (AISI 440C). X15TN X105CrMo17 (440C) Aspect of the surface after a 96 h salt spray (NaCl) exposure. For both grades, heat treatment cycle: 1050 °C Oil / -80 °C / 180 °C. UNS: S42025 Euro Number: 1.4123 14 X15TN X40CrMoVN16-2 Potentiocinetic corrosion in de-aerated H2SO4 - 1 % solution The following graph shows the response to this test. The superiority of X15TN over 440C (X105CrMo17) is confirmed. µA/cm2 10 000 X15TN 1075 °C / O 500 °C X15TN 1050 °C / O 450 °C X105CrMo17 1080 °C 480 °C X105CrMo17 1050 °C 150 °C X15TN 1050 °C / O 1800 °C > 5000 1000 Intensity (µA/cm2) 700 100 60 20 10 0 1 X15TN UNS S42025 X105CrMo17 440C VAR Current density results MACHINING The parameters presented below are indicative only. These parameters have to be optimized based on the type of machining, machines, tools, know-how... ANNEALED CONDITION Milling (insert) Roughing • Speed: 65 m/min • Feed: 0.15 mm/tooth • Depth: 2 to 5 mm • Intensive lubrication. Turning (insert) Roughing • Speed: 65 m/min • Feed: 0.50 mm/rev • Depth: 2 to 5 mm • Intensive lubrication. Finishing • Speed: 70 m/min • Feed: 0.12 mm/tooth • Depth: 0.3 to 1.5 mm • Intensive lubrication. Finishing • Speed: 70 m/min • Feed: 0.10 to 0.30 mm/rev • Depth: 0.3 to 0.5 mm • Intensive lubrication. Drilling (carbide tool) • Drill diameter: 3 to 30 mm • Cutting speed: 60 m/min • Feed: 0.07 to 12 mm/rev UNS: S42025 Euro Number: 1.4123 15 The information and the data presented herein are typical or average values and are not a guarantee of maximum or minimum values. Applications specifically suggested for material described herein are made solely for the purpose of illustration to enable the reader to make his own evaluation and are not intended as warranties, either express or implied, of fitness for these or other purposes. Aubert & Duval‘s liability shall not extend, under any circumstances, to the choice of the Product and its consequences. Design: - Aubert & Duval© 06/2010. Contact us: www.aubertduval.com
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