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Home , Silver, Titanium

W 2017 online update of ASM Handbook, Volume 6, , and Copyright # 2017 ASM International D.L. Olson, T.A. Siewert, S. Liu, and G.R. Edwards, editors All rights reserved www.asminternational.org

Brazing of Conventional Alloys*

Alexander E. Shapiro, Titanium Brazing, Inc.

THE BRAZING OF TITANIUM ALLOYS temperature and thermal treatment on structure titanium alloys at the temperature above b has been well studied and implemented in the and mechanical behavior of different classes of transus is not so critical. A loss of strength or industry over the past six decades. Now brazing titanium base such as commercially pure of the base can be recovered by is widely used in applications where a high spe- (CP) titanium, a or near-a alloys, a-b alloys, a post-braze heat treatment if necessary. cific strength-to-weight ratio as well as and b alloys. Classification, properties, and As practical, the brazing thermal cycle should resistance are critically important, for instance, potential heat treatment of titanium base alloys be in compliance with a typical heat treatment in aerospace and manufacturing, pet- are presented in Tables 2 and 3. cycle of the titanium to be brazed. Also, rochemical apparatuses, implants and prosthet- It is recommended that CP titanium, a or near- the design of the brazed structure should be taken ics, armors, chemical devices, and so forth. a alloys, as well as b titanium alloys, be brazed into consideration when selecting a brazing ther- Specific examples of brazed titanium parts in below the b transus temperatures in order to mal cycle. aircraft frames and engines are presented in avoid grain growth and transition that For example, titanium alloys that require cool- 1. may affect mechanical properties of titanium ing at a high rate or quenching from the brazing Because brazing is a thermal process often base metals. Such growth reduces ductility of temperature are not suitable for manufacturing involving the heating of whole parts to be brazed, base metals and can decrease mechanical proper- thin-wall structures such as honeycomb panels this article discusses the effects of brazing ties of the brazed structure. Brazing of a-b or fin-plate heat exchangers made from titanium foils. These brazed structures need slow cooling to avoid thermal deformation (Ref 3). Table 1 Brazed aerospace parts made of titanium alloys, titanium aluminides, and titanium matrix composites Selection of Brazing Filler Metals Service temperature Selection of filler metal depends on cost and Brazed structures C F Main stresses technical requirements to brazed joints: metal- , chassis, life-support systems lurgical compatibility to base materials, method Large-cell honeycomb wings and fuel tanks Ti alloys <400 <750 Tensile, fatigue of brazing, projected strength, work temperature, Stringer components of wings and rudders Ti alloys <100 <212 Tensile, fatigue corrosion resistance, and design of brazed joints. Sandwich-like wing sections Ti alloys <100 <212 Tensile, fatigue Metallurgical compatibility can be compared Fin-plate heat exchangers Ti alloys <600 <1110 Thermal fatigue according to Table 4 in order to select the Reverse grits for landing systems Ti alloys <600 <1110 Thermal fatigue, tensile Tubing and pipelines Ti alloys <150 <300 Shear, fatigue appropriate class of filler metals. Then, technical -titanium rotors of brake systems Ti alloys <400 <750 Shear, impact characteristics of filler metals represented in Bulletproof doors and other armor systems Ti alloys <100 <212 Impact Tables 5–10 should be carefully considered. Gas turbine and rocket engines A selected filler metal can be tested at different Wide-chord hollow fan blades Ti alloys <150 <300 Shear, fatigue process parameters to find out its suitability for Compressor vanes and diffusers Ti alloys <150 <300 Tensile, fatigue manufacturing the required brazed structure. Inlet guide vanes Ti alloys <100 <212 Shear, fatigue When selecting a filler metal, the method of Rotors, disks, and seals Ti alloys <150 <300 Tensile, fatigue brazing, and process parameters, one should Titanium-steel gears Ti alloys <300 <570 Shear, impact Turbine components TiAl, TMC(a) <900 <1650 Creep, thermal fatigue, tensile keep in mind that titanium forms brittle interme- Nozzles and nozzle flaps TiAl, TMC <900 <1650 Creep, thermal fatigue, tensile tallic compounds with almost all metal compo- Combustor case, turbine rear frame TiAl, TMC <900 <1650 Creep, thermal fatigue, tensile nents of filler metals. Therefore, is often Turbine and rocket gas diffusers TiAl, TMC <1000 <1830 Creep, thermal fatigue, tensile selected as a main component of the braze alloy, Collar and adaptor of combustion chamber Ti-6Al-4V <400 <750 Shear, thermal fatigue Acoustic tail pipes and cowls for engine noise reduction Ti alloys, TiAl <600 <1110 Shear, thermal fatigue because silver-titanium are suppo- Augmentor Ti alloys, TiAl <600 <1110 Shear, thermal fatigue sedly less brittle than intermetallics formed by Impellers Ti alloys <600 <1110 Shear, thermal fatigue titanium with other metals (Ref 12). Silver-base Low-pressure turbine vane TiAl <800 <1470 Creep, thermal fatigue, tensile filler metals typically used for brazing titanium Low-pressure turbine support TiAl <800 <1470 Creep, thermal fatigue, tensile Light-weight honeycomb panels Ti alloys, TiAl <600 <1110 Creep, thermal fatigue, tensile in or in air are presented in Table 9. Sometimes aluminum can be chosen as the (a) TMC, titanium-matrix composite. Source: Ref 1 main component of the braze alloy, because

* Collaborative publication of the American Welding Society and ASM International 2 / Brazing of Conventional Titanium Alloys

Table 2 Classification and typical properties of commercial titanium-base alloys

Annealing Tensile strength, strength, Service temperature, Alloy classification Composition, wt% Temperature of b transus(a), C(F) MPa (ksi) MPa (ksi) C(F) Time C(F) Commercially pure grades Grade 1 ... 900–955 (1650–1750) 240 (35) 170 (25) 650–760 (1200–1400) 0.1–2 h 540 (1000) Grade 2 ... 340 (49) 275 (40) Grade 3 ... 450 (65) 380 (55) Grade 4 ... 550 (80) 480 (70) a and near-a alloys Grade 6 Ti-5Al-2.5Sn 1030 (1890) 790 (115) 760 (110) 720–845 (1330–1550) 0.2–4 h 480 (900) UNS R54520 UNS R54810 Ti-8Al-1Mo-1V 1040 (1900) 900 (131) 830 (120) 760–815 (1400–1500) 1–8 h 595 (1100) UNS R54620 Ti-6Al-2Sn-4Zr-2Mo 995 (1820) 900 (131) 830 (120) 870–925 (1600–1700) 0.5–1 h UNS R56210 Ti-6Al-2Nb-1Ta-0.8Mo 1015 (1860) 790 (115) 690 (100) 790–900 (1450–1650) 1–4 h a-b alloys Grade 5 Ti-6Al-4V 995 (1820) 900 (131) 830 (120) 705–790 (1300–1450) 1–4 h 400 (750) UNS R56400 Grade 9 Ti-3Al-2.5V 935 (1715) 620 (90) 520 (75) 650–760 (1200–1400) 0.5–2 h AMS 4943 UNS R56620 Ti-6Al-2Sn-6V 945 (1735) 1030 (149) 970 (141) 705–815 (1300–1500) 1–4 h a-b (near-b) alloys UNS R56260 Ti-6Al-2Sn-4Zr-6Mo 932 (1710) 1270 (184) 1170 (170) 705–730 (1300–1350) 2 h 400 (750) UNS R58650 Ti-5Al-2Sn-2Zr-4Cr-4Mo 870 (1600) 1105 (160) 1075 (156) 800–860 (1470–1580) 2–4 h AMS 4995 UNS R56410 Ti-3Al-10V-2Fe 805 (1480) 1170 (170) 1100 (160) 790–815 (1450–1500) 6–15 min AMS 4983 b alloys Grade 21 Ti-15Mo-3Nb-3Al-0.2Si 807 (1485) 1330 (193) 1250 (181) 816–843 (1500–1550) 20–30 min 593 (1100) UNS R58210 (Timetal 21S) UNS R58030 Ti-11.5Mo-6Zr-4.5Sn 760 (1400) 1380 (200) 1250 (181) 705 (1300) 0.2–1 h 400 (750) AMS 4977 UNS R58820 Ti-8Mo-8V-2Fe-3Al 775 (1420) 1170 (170) 1100 (160) 774–790 (1425–1450) 0.1–0.25 h UNS 58010 Ti-13V-11Cr-3Al 675 (1248) 1276 (185) 1207 (175) 705–790 (1300–1450) 0.2–1 h AMS 4917 Grade 19 Ti-3Al-8V-6Cr-4Mo-4Zr 795 (1450) 1450 (210) 1380 (200) 705–815 (1300–1500) 0.3–0.5 h UNS R58645 (a) ±20 C. Source: Ref 2

Table 3 Solutioning and aging heat treatments for commercial titanium-base alloys alloying a brazing filler metal with , mag- nesium, , , or especially , Solutioning Aging and (b) using a short brazing time and fast cool- Alloy C F Time, h C F Time, h ing from the brazing temperature. The strength a-b alloys of joints can be improved by using a mechani- Ti-6Al-4V 900–970 1652–1778 0.2–1 480–510 896–950 4–24 cally secured joint design, and fillets of joints Ti-3Al-2.5V 870–930 1598–1706 0.25–0.3 480–510 896–950 2–8 can be protected against corrosion by using poly- Ti-6Al-2Sn-6V 840–900 1544–1652 0.2–1 470–620 878–1148 2–8 mer, phosphate, or other coatings. a-b (near-b) alloys Titanium-base or -base filler Ti-6Al-2Sn-4Zr-6Mo 840–930 1544–1706 0.2–1 565–620 1050–1148 2–8 metals provide not only higher shear or tensile Ti-5Al-2Sn-2Zr-4Cr-4Mo 815–860 1500–1580 4 620–650 1148–1202 8 strength of brazed joints of titanium alloys but Ti-3Al-10V-2Fe 790–815 1454–1500 1 495–525 922–978 8 also high corrosion resistance. This is important b alloys for applications in marine environments, as Ti-15Mo-3Nb-3Al-0.2Si (Timetal 21S) 816–843 1500–1550 0.1–0.5 510–679 950–1254 8–16 well as in the manufacture of heat exchangers Ti-11.5Mo-6Zr-4.5Sn 730–790 1346–1454 0.2–1 480–590 896–1094 8 or medical devices. For example, brazed joints Ti-8Mo-8V-2Fe-3Al 760–900 1400–1652 1–2 620 1148 4 of titanium grade 4 made by using BTi-3 preal- Ti-13V-11Cr-3Al 760–815 1400–1500 0.2–1 440–540 824–1004 2–60 Ti-3Al-8V-6Cr-4Mo-4Zr 815–930 1500–1706 0.5 480–590 896–1094 6–12 loyed powder and exposed at 260 and 538 C (500 and 1000 F) in a media exhibited only slight degradation of the mechanical prop- aluminum has a limited zone of solutions source (Ref 8). However, silver-base and alumi- erties of the joints but no visible corrosion with titanium that allows to count on the forma- num-base brazing filler metals have some serious attack of the filler metal or the brazed joints tion of low brittle brazed joints. Another advan- disadvantages: (a) low corrosion resistance, (b) (Ref 13). Amorphous foils of BTi-5, tage of aluminum-base filler metals is their low the strength of brazed joints is lower than that TiBraze590, and TiBraze800 (Table 7) exposed liquidus—in the range of 525 C (980 F) for of titanium-base or zirconium-base brazing filler for 1000 h in 5% salt fog according to ASTM Al-Cu-Si brazing alloys to 645 C (1190 F) for metals (Ref 12), and (c) relatively low admitted B117-11 also showed no trace of corrosion Al-Mg or Al-Mn brazing alloys (Table 8)—that working temperature of brazed joints (<400 C, (Ref 10). These filler metals have a working allows brazing of any titanium base metals, or 750 F, for most silver-base filler metals, and temperature up to 600 C (1110 F) and allow including b alloys, below a$b transformation <250 C, or 480 F, for most aluminum-base such heat treatment operations as aging or solu- (Ref 9). Additionally, some aluminum-base filler filler metals). tion treatment after brazing or together with metals can be used for brazing titanium in air The growth of intermetallics in aluminum- brazing in the same thermal cycle. Metallurgi- using a propane torch or HF inductor as a heating brazed joints can be partially suppressed by: (a) cal compatibility should be checked according