Machining nickel alloys

1 NiDl nickel Development Institute Machining nickel alloys A nickel Development Institute Reference Book, Series No 11 008. Table of Contents Acknowledgments .. i Abbreviation key .. i Introduction .. ii nickel alloys and machinability .. 1. Basic principles applicable to all Machining operations .. 3. Work hardening .. 3. Choice of cutting tools .. 3. Lubricants and coolants .. 4. Recommendations for Machining .. 5. Turning, boring and grooving .. 5. High speed steel tooling .. 5. Carbide tooling .. 6. Ceramic tooling .. 7. Insert selection and method of use .. 9. Taking the correct tool path .. 12. Drilling .. 12. Twist drills .. 12. Insert drills .. 12. Deep hole drilling .. 13. Deep hole drilling by non-traditional methods .. 14. Reaming .. 14. Tapping and threading .. 15. Planing and shaping .. 16. Broaching .. 16. Milling .. 17. Conventional milling cutters.

2 17. Electrochemical, electrical discharge, and chemical milling .. 18. Sawing .. 19. Grinding and surface finishing .. 20. References .. 22. Acknowledgements Much of the information in this publi- detailed information on the use of cation was derived from publications and ceramic tooling. We are especially data provided by the manufacturers of grateful to Inco alloys International, Inc. nickel alloys and cutting tools, and the for allowing us to use much of the cooperation of the companies providing material contained in their excellent this information is appreciated. The brochure entitled Machining Inco alloys Greenleaf Corporation was especially International Products. helpful in providing discussion and Abbreviation key Depth of cut DOC inches (inches). mm (millimetres). Feed rate ipr inches per revolution mm/rev millimetres per revolution Cutting speed sfm surface feet per minute m/min metres per minute i Introduction The Machining of nickel and nickel -base that is employed.

3 For example, tooling alloys can be readily accomplished which is optimum for the annealed providing fundamental principles affecting condition may not be the best choice for their machinability are understood and hardened material. taken into consideration. Compared to In recent years there have been a other materials, the most significant number of advances in cutting tools and characteristic of nickel alloys is that they methods applicable to the Machining of are usually much stronger at metal cutting nickel alloys . This publication gives an temperatures. Consequently, powerful overview on Machining nickel alloys using and rigid machines provide the best traditional methods and describes the results and often are essential for advances that have been made. A number successful Machining . Corollary to these of very good and useful guides and property and machine requirements is that reference books on the Machining of nickel tooling be selected to minimize cutting alloys have appeared over the years.

4 They forces, to have maximum edge strength, are listed in the References and should be and to withstand the highest possible consulted for detailed information on cutting temperatures. Machining conditions. The information in In addition to an appreciation of the this brochure is based on the experience of basic properties of nickel alloys them- producers and users of nickel alloys , and selves, of paramount importance to suppliers of cutting tools. This information successful Machining is an understanding should be considered only as a starting of basic principles that come into play in point in developing a Machining program relation to the particular alloy, and the which then may require optimization to suit method of Machining or tooling specific conditions. ii nickel alloys and machinability nickel alloys are used primarily in appli- high strength and oxidation resistance at cations involving electrical properties or elevated temperatures.

5 A great many requiring good corrosion resistance or alloys exist to meet these demanding Table I nickel alloys grouped according to Machining characteristics. Group Group Characteristic Alloy UNS # Ni Cu Fe Cr Mo Co AI Ti Nb Other alloys containing essentially nickel for caustic alkali chemical Alloy 200 N02200 C 0 08. and electrical applications. Lowest strength and work Alloy 201 N02201 C A hardening of the nickel alloys . Exhibits gummy behaviour in Alloy 205 N02205 Mg , C the annealed condition; hardenable only by cold working Alloy 212 Mn , C which provides the best condition for Machining . Alloy 222 Mg Alloy 400 N04400 nickel -copper and nickel -iron alloys for sulfuric acid and Alloy 401 N04401 Mn corrosion, and electrical applications. Have higher strength Alloy 450 C71500 Mn B work hardened than Group A alloys . Most alloys cannot be Alloy 36 K93600 hardened by heat treatment and best Machining is obtained Alloy K K94610 in cold-drawn or cold-drawn and stress-relieved conditions.

6 Alloy MS 250 Alloy 600 N06600 Alloy 690 N06690 Alloy 601 N06601 Alloy 825 N08825 Mainly nickel -chromium and nickel -iron-chromium Alloy DS Si alloys for acid and high temperature corrosion Alloy 330 N08330 Si C applications. Similar in mechanical properties to austentic Alloy 20 N08020 stainless steels except for greater high temperature strength. Alloy 800 N08800 C These alloys are best machined in the cold-drawn or cold- Alloy 800HT N08811 Al+Ti C drawn and stress-relieved conditions, Alloy 802 N08802 C Alloy 270 N02270 C Alloy K-500 (unaged) N05500 Alloy 75 N06075 Alloy 86 Ce This group consists of a limited number of age-hardened Alloy 301 N03301 D-1 alloys in the solution annealed condition. These alloys are Alloy 925 N09925 relatively easily machined. Alloy 902 N09902 Alloy 301 (aged) Alloy K-500 (aged) N05500 Alloy 902 (aged) N09902 Alloy 81 Alloy G-3 N06985 W.

7 05. Alloy HX N06002 218 Alloy 625 N06625 This group consists of Group D-1 alloys in the Alloy 925 (aged) N90925 age-hardened condition, most other age-hardenable Alloy 716 N07716 alloys in both the solution annealed and hardened Alloy 725 N07725 conditions, and some highly solution strengthened Alloy MA 754 N07754 Y 0 alloys . They contain strong solution strengtheners and Alloy 80A N07080 D-2 hard abrasive precipitates which make Machining difficult. Alloy 718 N07718 These alloys should be rough machined in the solution Alloy PE11 annealed condition and then finish machined after aging. Alloy 706 N09706 A size contraction up to about takes place upon Alloy PE16 aging which must be allowed for in rough Machining . Alloy C-276 N10276 W , Mn Alloy 751 N07751 Alloy X-750 N07750 Alloy 901 N09901 Alloy 617 N06617 Alloy 263 N07263 Alloy 105 Alloy 90 N07090 Alloy PK50 Alloy 115 Alloy B-2 N10665 Si Alloy 903 N19903 Alloy 907 N19907 Si Alloy 909 N19909 Si E A special Alloy 400 designed to be free Machining Alloy R-405 Mn , S for high production on automatic screw machines.

8 1. applications, but they all have some A different set of Machining conditions is properties in common which effect their applicable to each category, and the first machinability to a varying degree. They all step for successful Machining is for the have an austenitic structure which imparts programmer/machinist to identify the properties of high ductility and work applicable category for the alloy to be hardening, producing a gummy Machining machined. A listing of the common nickel behaviour similar to that of austenitic alloys found in each category is also stainless steels. In addition, those alloys provided in Table l. The metallurgical designed for high temperature applications condition for some alloys must also be remain strong at the temperatures of chip known for proper category classification. formation during Machining , and thermal As can be seen from Table l, many of the conductivity is much less than that of steel factors that define each category are those and many other materials.

9 The age discussed above in relation to nickel alloys hardening nickel alloys also contain in general. The relative importance of each abrasive titanium and aluminum particles. factor, however, changes from category to It is these factors that make nickel alloys category. This is illustrated for mechanical more difficult to machine than steel, and it properties in Figure 1, where a comparison is an understanding of the extent to which is made to stainless and carbon steel. As each nickel alloy is affected by these one moves from steel to stainless and then factors which is the key to their successful to the nickel alloys , ductility, work harden- Machining . ing and high temperature strength gradually nickel alloys are classified into different increase, denoting more difficult Machining categories according to their relative and, correspondingly, altered Machining Machining behaviour as shown in Table I.

10 Conditions. Figure 1 nickel alloys grouped according to increasing mechanical properties and resultant increasing difficulty to machine. 2. Basic principles applicable to all Machining operations Work hardening and grooving tools, or operations involving interrupted cuts usually require The avoidance of work hardening is of high-speed tools chosen on the basis of fundamental importance to the successful toughness. These tools must be run at Machining of all nickel alloys . Work quite low speeds, but they are often the hardening occurs when the metal ahead only choice available with small tooling. of the cutting tool, especially one that is When the operation allows for larger cutting poorly, is plastically deformed. tools, carbide provides a good first choice This hardened layer is very difficult to for turning and some milling and drilling penetrate in subsequent passes or operations.