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MMPDS-01 31 January 2003 Cold Forming — Almost all of the wrought-nickel-base alloys in sheet form are cold formable. The lower strength alloys offer few problems, but the higher strength alloys require higher forming pressures and more frequent anneals. Machining — All of the alloys in this section are readily machinable, provided the optimum conditions of heat treatment, type of tool speed, feed, depth of cut, etc., are achieved. Specific recommendations on these points are available from various producers of these alloys. Welding — The matrix-strengthening-type alloys offer no serious problems in welding. All of the common resistance- and fusion-welding processes (except submerged arc) have been successfully employed. For the age-hardenable type of alloy, it is necessary to observe some further precautions: (1) Welding should be confined to annealed material where design permits. In full agehardened material, the hazard of cracking in the weld and/or the parent metal is great. (2) If design permits joining some portions only after age hardening, the parts to be joined should be “safe ended” with a matrix-strengthened-type alloy (with increased cross section) and then age hardened; welding should then be carried out on the “safe ends.” (3) Parts severely worked or deformed should be annealed before welding. (4) After welding, the weldment will often require stress relieving before aging. (5) Material must be heated rapidly to the stress-relieving temperature. (6) In a number of the age-hardenable alloys, fusion welds may exhibit only 70 to 80 percent of the rupture strength of the parent metal. The deficiency can often be minimized by design, such as locating welds in areas of lowest temperature and/or stress. The use of special filler wires to improve weld-rupture properties is under investigation. Brazing — The solid-solution-type chromium-containing alloys respond well to brazing, using techniques and brazing alloys applicable to the austenitic stainless steels. Generally, it is necessary to braze annealed material and to keep stresses low during brazing, especially when brazing with low melting alloys, to avoid embrittlement. As with the stainless steels, dry hydrogen, argon, or helium atmospheres (-80EF dew point or lower) are used successfully, and vacuum brazing is now receiving increasing attention. The aluminum-titanium age-hardened nickel-base alloys are difficult to braze, even using extremely dry reducing- and inert-gas atmospheres, unless some method of fluxing, solid or gaseous, is used. An alternative technique which is commonly used is to preplate the areas to be brazed with ½ to 1 mil of nickel. For some metal combinations, a few fabricators prefer to apply an iron preplate. In either case, the plating prevents the formation of aluminum or titanium oxide films and results in better joints. Most of the high-temperature alloys of the nickel-base type are brazed with Ni-Cr-Si-B and Ni-Cr-Si types of brazing alloy. Silver brazing alloys can be used for lower temperature applications. However, since the nickel-base alloys to be brazed are usually employed for higher temperature applications, the higher melting point, stronger, and more oxidation-resistant brazing alloys of the Nicrobraz type are generally used. Some of the gold-base and palladium-base brazing alloys may be useful under some circumstances in intermediate-temperature applications. 6-20
MMPDS-01 31 January 2003 6.3.1 HASTELLOY X 6.3.1.0 Comments and Properties — Hastelloy X is a nickel-base alloy used for combustorliner parts, turbine-exhaust weldments, afterburner parts, and other parts requiring oxidation resistance and moderately high strength above 1450EF. It is not hardenable except by cold working and is used in the solution-treated (annealed) condition. Hastelloy X is available in all the usual mill forms. Hastelloy X is somewhat difficult to forge; forging should be started at 2150EF to 2200EF and continued as long as the material flows freely. It should be in the annealed condition for optimum cold forming, and severely formed detail parts should be solution treated at 2150EF for 7 to 10 minutes and cooled rapidly after forming. Machinability of Hastelloy X is similar to that of austenitic stainless steel; the alloy is tough and requires low cutting speeds and ample cutting fluids. Hastelloy X can be resistance or fusion welded or brazed; large or complex fusion weldments require stress relief at 1600EF for 1 hour. Hastelloy X has good oxidation resistance up to 2100EF. It age hardens somewhat during long exposure between 1200EF and 1800EF. Some material specifications for Hastelloy X are presented in Table 6.3.1.0(a). Room-temperature mechanical and physical properties for Hastelloy X sheet are presented in Table 6.3.1.0(b). AMS 5754 does not specify tensile properties for bars and forgings. Figure 6.3.1.0 shows the effect of temperature on physical properties. Table 6.3.1.0(a). Material Specifications for Hastelloy X Specification Form Condition AMS 5536 AMS 5754 Sheet and plate Bar and forging Solution heat treated (annealed) Solution heat treated (annealed) 6.3.1.1 Annealed Condition — The effect of temperature on various mechanical properties is presented in Figures 6.3.1.1.1 and 6.3.1.1.4. In addition, certain stress-rupture requirements at 1500EF are specified in AMS 5536 and 5754 for Hastelloy X. Typical tensile stress-strain curves at room and elevated temperatures are presented in Figure 6.3.1.1.6(a). Typical compressive stress-strain and tangent-modulus curves at room and elevated temperatures are presented in Figure 6.3.1.1.6(b). 6-21
Page 1 and 2: MMPDS-01 31 January 2003 CHAPTER 6
Page 3 and 4: MMPDS-01 31 January 2003 6.1.1 MATE
Page 5 and 6: MMPDS-01 31 January 2003 6.2.1.1 So
Page 7 and 8: MMPDS-01 31 January 2003 Figure 6.2
Page 15 and 16: MMPDS-01 31 January 2003 6.2.2 N-15
Page 19: MMPDS-01 31 January 2003 6.3 NICKEL
Page 25 and 26: MMPDS-01 31 January 2003 60 .5 -hr
Page 27 and 28: MMPDS-01 31 January 2003 6.3.2 INCO
Page 29 and 30: MMPDS-01 31 January 2003 Table 6.3.
Page 33: MMPDS-01 31 January 2003 Next page

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