. . . TOFT ORNL P 3102 - . I " • ** . . n . - Mu EEEEEEEE 1.425 || 1.4 1.1.6 MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS - 1963 1 : 46 w. . ! . . SP . Panoraad, 2102 Contac70605.-3. . MASTER ete R JUN 2 2 1969 .600 . ENAULT CFSTI PRICES Ha $3.00, MN.65 1. Predy . . . . A .. . . .. . . . : . . L. ." 2 APPLICATION OF CHEMICAL VAPOR DEPOSITION TO THE PRODUCTION OF TUNGSTEN TUBING- 5. W. R. Martin, R. L. Heestand, 2 R. E. McDonald, and G. A. Reimann Metals and Ceramics Division Oak Ridge National Laboratory ..: Oak Ridge, Tennessee 1 ... - + 4 * - -. . A A V .. . A. V A ' . . .. LEGAL NOTICE . - - M I I . i 'This soport mao prepared u an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: representation, expressed or implied, with respect to the acou- !racy, completenjes, or usefulness of the information contained in this report, or that the use . of way Information, apparatus, method, or procon declosed la this report may not infringo privately owned righto; or B. Assuas any liabilities with rospect to the who of, or for damages resulting from the uno of any information, apparatus, method, or procodi disclosed in this report. . As und in the above, "person acting on beball of the Commission includes any om- .. ploys or contractor of the Commission, or employee of such contractor, to the extent that suoh employs or contractor of the Commission, or employee of such contractor prepares, Monminator, or provides accous to, any information purwant to his employment or contrnot : with the Commission, or his employment with such contractor. - . ..-.. . A . ,-. 1 ..". Dans . . Number of Pages: 10 Number of Figures: Number of Tables: 3 1 - IT AL . .. DISTRIBUTION OE THIS DOCUMENT, (S UNLIMITED . . . . - "'!:,: . .:7* .*:*:..: ... - .. . -" :-*,7... . : i ..41- Fü ... ALT TIE: . LY THE 41. .. . TA TAR . . * RT * Ty-- . + T 2. OF IT " ht TTTT 9 PRODUCTION OF CVD TUNGSTEN TUBING 12 - W. R. Martin Metals and Ceramics Division Oak Ridge National Laboratory : P. 0. Box X Oak Ridge, Tennessee 37830 14 . . .. .. : . -. . . . .. . . . .....: . .." 2. Botig!! i 7 1,1!11. O il cin771? Trillo ABSTRACT Chemical vapor deposition is used in the production of tungsten *MARGIN metal products as an aid in the fabrication of arc-cast, electron-beam- melted, and powder-metallurgy products and as a direct process for producing tubing. The direct process can be used to make tube shells for further working or tubing in its final form. The 9.8-deposited structure of the chemical vapor-deposited tungsten may be sufficient and/or desirable for some specific applications. Simple shapes such as tubing in lengths up to nearly 4 ft can be made easily and are less expensive than equivalent tubing made by the conven- tional extrusion-drawing method. Such tubes can be made in various diameters with wall thickness variations not exceeding +0.001 in. in the as-deposited condition. Therefore, this method 18 attractive for making shorter lengths of tubing of higher purity (less than 25 ppm total metallic impurities). If the as-deposited structure of chemical vapor-deposited tungsten is undesirable, tube shells for further working can be made by chemical vapor deposition. These tube shells can be worked conventionally, as by extrusion and drawing. The microstructure of chemical vapor-deposited material after working 13 comparable to that of arc-cast or yowder- 1. metallurgy products. If the amount of drawing is' reduced to a few · passes, the cost of worked chemical vapor-deposited tubing would be less than that of conventional tungsten tubing. I. INTRODUCTION The fabrication of refractory metals 18 more difficult than that of iron- and nickel-base alloys. The techniques and tooling that have been developed to produce tubing from the "conventional" alloys are not optimal for tungsten. Tungsten metal shapes, such as sheet and tubing, are being fabricated to meet geometric requirements, but we are engaged in a research and development effort to improve the fabrication technol- ogy of refractory metals. An interesting new process for making complex shapes of tungsten 14111:11? is chemical vapor deposition (CVD). Since 1963, ORNL has been investi- gating the process of UVD in terms of both deposition parameters and innovations needed to make sheet and tubing of consistent quality in practical sizes and quantities. This report will convey our current ideas on the production of tungsten tubing by CVD. II. FABRICATION TECHNIQUES The variety and the range of tubing sizes routinely produced are shown in Fig. 1. Tubing sizes range from 0.020 into larger than 1 in. with the desired wall thickness. In making CVD tungsten tubing, one can choose between making a final product having the as-deposited grain structures or a wrought structure obtained by working the as. deposited material. In the latter case, there is the option of producing an end product of either a cold-worked, hot-worked, or recrys- tallized structure. In this respect, these methods have an advantage over as-deposited CVD tungsten. These two distinctly different approaches are illustrated in Fig. 2. . . 14.A. C A W - * a * ST LINE I TEMI : "CHAOTIATIVE ... 1. As-Deposited Tubing MARIN Process A constitutes the production by direct CVD. The general process for making shorter lengths of tubing has been described previ- ously (1). Recently we have made 3. to 4-ft lengths of tubing using a resistance-heated mandrel. These tubes characteristically have uniform walls and represent an improved method for making pure metal deposits. The deposition is done in a water-cooled chamber fitted with insulated electrodes at each end. The apparatus is operated in the vertical posi- tion, and the resistance element is kept straight by a weight applied to the retractable bottom electrode. Thin-wall stainless steel tubing is drawn to the outside diameter equal to the desired inside diameter: of the tungsten tube required. This tubular mandrel in addition to giving suitable resistance for heating, allows installation of an internal thermocouple to monitor the deposition temperature. The power supply for the resistance heating 18 a 300-amp welding machine in which the power output may be continuously adjusted to maintain the desired deposition temperature. The WFG-Ha reduction technique (1) is used to produce the deposit. 1 Uniformity of dessition in this scheme is enhanced by the resis- tance behavior of the substrate. Areas that are low in tungsten have a higher current density, which raises the temperature locally, thus increasing the deposition rate and giving uniformity. This method, of course, requires that sufficient amounts of reactants be present to ensure a uniform tube wall. For a 0.200-in.-ID tube deposited at 650°C, · 100 cm/min WF6 and 2100 cm /min Ha at a pressure of 10 torrs will give I a deposit rate of 0.0055 in./hr at an efficiency greater than 90%. At INING ! : - io!!! EL" ; this deposition rate, a 40-in. tube can be produced per day with a PIR ili 1. Ved WP Wave ) ** wall thickness up to 0.030 in. Due to the difference in coefficient of expansion between the stainless steel mandrel and the tungsten deposit, the tungsten tube can be readily removed from the mandrel after cooldown. No parting agent is necessary, since the tungsten does not bond to the thin oxide film that forms on the stainless steel mandrel. Such tubing lengths are suitable for use in the as-deposited condition but may be ground to improve the outer finish. The inside surface is normally very smooth, depending upon the surface of the mandrel used during deposition. * * . 4 SW 2. Working of CVD Tube Shells In the second process (B), a heavy-wall tube shell of CVD tungsten is made for extrusion. Deposits of this type are prepared by depositing thicknesses up to 0.300 in. on the inside of a TZM extrusion billet jacket or on the outside of a molybdenum sleeve. We have extruded CVD tungsten tube shells produced by each technique and extruded and hot plug drawn the CVD duplex extrusion produced by the latter technique. A photograph of the as-deposited CVD tube shell and an exploded view of the duplex billet prior to extrusion are shown in Fig. 3. After extrusion, one has a duplex tube with the CVD tungsten clad with the billet jacketing material, as shown on the right in Fig. 4. The duplex tube is then hot drawn over a plug to obtain a size suitable for subse- quent mandrel drawing. The extrusion and drawing conditions are given in Tables I and II, respectively. The reduction per pass varied from : 21 to 38%. A total of 85% deformation was obtained in five passes with one intermediate stress relief at 1200°C for 0.3 hr'. .. .. L . TEL : .. RUTE Yuki viewed OTTO!!!!! !?7 l.INIE (1 OR? CHAPTER TITIL The microstructures in the as-deposited, extruded, and drawn va conditions are given in Fig. 5. The columnar structure found in the as-deposited condition is not present after extrusion. A partially recrystallized structure is observed after extrusion at 1700°C. This structure may be fully recrystallized by heating for 1 hr at 2000°C, as shown in Fig. 6. A completely wrought structure is obtained by working at 700°C. We are presently studying the recrystallization behavior of this wrought structure. Preliminary data indicate that a partially recrystallized 'structure is produced by heat treating the CVD tungsten after the fifth drawing pass for 0.3 hr at 1200°C. This structure is shown in Fig. 6. No recrystallization was observed for material simi- larly heat treated after the third drawing pass. LEET MANS'i III. ECONOMICS OF PRODUCING TUNGSTEN TUBING BY CHEMICAL VAPOR DEPOSITION In addition to evaluating the metallurgical structure and tubing that one can obtain by CVD, the cost of making CVD products must be considered. This is not an attempt to evaluate the profit potential of the CVD process, but rather to indicate the economics relative to other fabrication techniques. First, consider the methods of tubing production other than CVD. Billets for extrision must be prepared by arc casting, electron-beam melting, or powder-metallurgy techniques. These billets are extruded into thin-wall shells by multiple extrusions, commonly referred to as primary and secondary (duplex) extrusions. Tube shells are then warm mandrel drawn, which requires a small reduction per pass; consequently seamless thin-wall, small-diameter tubing requires many passes. An . . BAHIAIN115!! 17. - . alternate to seamless tubing is welded tubing. The billets are extruded into heavy sheet bar, which is warm or hot rolled into thin sheet. The sheet is shaped into tubular form and welded. The welded tubing is warm mandrel drawn to work the weld bead area and heat-affected zones. These methods are outlined in Fig. 7. Using these conventional modes of tubing manufacture, long lengths of high quality tungsten tubing have been produced. Normally, welded tubing is less expensive than seamless tubing, but the cost differential is usually less than 20 or 30%. The major cost is related to the many metalworking steps. On the other hand, tubing can be made directly by CVD employing relatively inexpensive equipment. For example, the 4-ft length of 0.020-in.-wall tubing discussed earlier was deposited in one 4-hr run. An additional hour to centerless grind the outer surface yields a total manpower requirement of 5 hr per 4-ft length of tubing. One man can work with several deposition chambers simultaneously, perhaps as many as 5 or 6. The lower time factor for CVD tubing is a great advantage. Fewer process steps and less operation time greatly lower the inventory neces- sary to meet customer demand and delivery dates. These factors lower the variable costs normally associated with tubing production. In addition, CVD requires low fixed and capital costs. Relative to arc :; cast, electron-beam, and powder-metallurgs“ products, the starting mate- rials for CVD are presently higher. Tungsten costs $13.00/10 as WF6, compared with $4.50/10 for tungsten powder. One would anticipate that WFG could be made from the same grade ore as 18 now hydrogen-reduced to -;-..'.... .. :: . : . . . .Si... . Tui . .. 9. BOMY0:1 RST JE OR TI CHANTER z. tungsten powders. In this way, the intermediate and unnecessary step of making turgsten powders for fluorination would be eliminated and the cost of WF'could be reduced. However, this higher cost of tungsten is offset by the lower costs associated with process equipment. The cost of an extrusion press and drawbench is much higher than that of deposi- tion chambers and associated equipment. . . If CVD is used to produce tube shells that are extruded, drawn, etc., then the cost of CVD tubing increases and approaches the cost of the conventionally produced product. Absolute cost numbers are subject FT. MARTENS to numerous considerations, many of which are not applicable throughout industry, but we have determined the relative cost of several sizes 'T of tubing made by each of three routes. Route A denotes tubing made by direct deposition. Route B represents CVD tubing thac is cold worked into final form. Route C denotes arc cast or powder-metallurgy product that is subsequently extruded and drawn. The costs shown in Table III P . consider the cost of the starting materials, machining costs within the fabrication schedule, and manpower costs for all the operations. One can readily see that the cost of small-diameter, thin-wall 'CVD tubing is one-third that of conventionally prepared seamless tubing. For heavy- wall tubing, the cost of CVD material approaches that of the conventionally prepared arc cast or powder-metallurgy product. A small reduction in the .. cost of CVD tubing will be realized if the price of Wig can be reduced. At $13.00/1b, the cost of WF6 represents 16 and 9% of the total cost for heavy-wall and thin-wall tubing, respectively. For example, a 50% · reduction in the cost of WF6 would lower the price of heavy-wall tubing by approximately 10%. OF TYPI . : . - . -- '. 10 These analyses are not to imply that as-deposited CVD tubing should completely replace wrought tubing because certain other characteristics . * . - 640 of wrought tubing are needed for some applications. However, CVD tubing does have properties suitable for many applications and it is therefore economically competitive. The economic evaluation just described is not precise, but with a low fixed- and capital-cost process, profit margins can be derived from low-volume orders. IV. CONCLUSIONS Chemical vapor deposition is a process' by which high-purity tungsten tubing may be made in lengths up to 4 ft in various diameters and wall thicknesses. In the as-deposited form, this product is less costly than tubing produced by the more conventional routes of arc casting, electron-beam melting, and powder metallurgy, followed by extrusion, drawing, and annealing operations. * If the as-deposited structure of this material is undesirable, the CVD product can be worked to produce a material with a wrought structure: or a controlled grain size. However, the working operations will increase the cost of the tubing so that it approaches the cost of the conventional . .. . ;. . - - . UT10:10 1:11 ON TEXT FOOTNOTES 1. Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation. . 2. Now at Battelle Memorial Institute, Columbus, Ohio. : 10 . .. KED .. .. ......MAFUV-21.-' AVIS . 4 REFERENCES . 1 1. R. L. Heestand, J. I. Federer, and C. F. Leitten, Jr., Preparation and Evaluation of Vapor-Deposited Tungsten, ORNL-3662 (August 1964). th . TC . .. . -. .11 . . 623 .. . . SKY VOTRE . . 2 . D - . . - miin . X 2 " . . . .! . UNN $ . . .4FAN... i . i .stir . . 17.25. .."" . *. ' . . . . 1 . . TAINING 01 JYPIS ..o ! ia . ! . EFT MARGIN:.. OR CHAPTER TITLE=; FIRST LINE OR TEXT OOTTOM OF : :: : .. , di Table I Extrusion Data for CVD Tungsten . . . .:: . . :II . : . . Extrusion : Number Billet Weight Extm Extrusion Billet Si Diameter Outside Inside Length arameters (16) Temperature :.. Ratio Extruded Tube Shell Size (in.) Diameter Outside Inside 325 2.985 0.815 6.0 14,6 1760 .- * w : : 7.4 326 2.955 0.815 5.9 14.4 1700 - PRIYAL 1.310 1.305 1.264 0.718 0.753 0.724 327 2.990 0.815 7.8 8.1. 6.0 14.6. 1700 --. S - . a E . . P ' A * ** - PTER Till INE OR TY 30 101,- for . . Table II Drawing and Heat Treating Schedules for Composite Tube Reduction of Area Number Dimensions of CVD Tungsten (in.) Outside Wall Diameter Heat Treatment Prior to Pass Per Pass Total 0.816 0.031 0.3 hr at 1200°C 0.775 0.022 None u AwNN 0.747 0.017 None 1. 38. 35 • 32.5 : 25.5 21.0 38 60 73 80 85 CLASSS! 0.724 0.708 0.013 0.010 0.3 hr at 1200°C None ?10 : .. .... : : .. " OTTO!A OLE 1 LINT OF TEXT CHAITEN TITLE Table IJT Relative Cost of CVD and Wrought Tubing Size of Tubing (in.) Diameter Outside Inside Tubing Cost per Unit Length Using Process: А T AILS!!! 1.6 0.86 0.73 1.0 0.75 0.67 4.28(x) 6.3(x)& 1.31(x)@ 3.5(x)@ 3.8(*)& (xj& 2-3(x) 3.2(x)& NT IN The basic cost of the thin-wall small- diameter CVD tubing is represented by X. ut. SP LIST OF FIGURES Fig. 1. (Y-78174) Various Sizes and Configurations of CVD Tubing · Now Available. Fig. 2. (Original drawing) Basic Approaches to the Production of CVD) Tubing. Fig. 3. (Y-79742, ORNL-Photo 80792) Photographs of (a) CVD Tube Shell Prior to Extrusion and (b) Exploded View of Duplex Extrusion Billet. Fig. 4. (Y-62710) Photographs of Extruded Tungsten Tubing: On the right, the as-extruded shell is shown with the molybdenum TZM jacketing. After the jacket material is removed by chemical dissolution, the tungsten tubing is as shown on the left. Fig. 5. (Y-68529, 7-77742, Y-78346) Microstructures of the As. Deposited, Extruded and Drawn CVD Tungsten. (a) As-deposited; (b) as- extruded at 1700°C and 8:1 reduction; and (c) as-drawn at 700°C (85% . reduction). Fig. 6. (Y-78348, Y-79801) Microstructures of Extruded and Drawn CVD Tungsten after Heat Treatment. (a) Partial recrystallization of CVD tungsten having 85% hot work at 700°C and heat treated for 0.3 hr at 1200°C. (b) Complete recrystallization of CVD tungsten having been extruded at 1700°C (8:1 reduction) and heat treated for 1 hr at 2000°C. Fig. 7. (Original drawing) Fabrication Routes for Production of Tungsten Tubing. * T 7 . . , .,P . 1 :. re . . ELE . : .", . it . . ity . ! F . . . wie p Heavy Wall - Large Diameter Š ONE INCHI : - - Thin Wall - Large Diameter - - - *M t ot. .. 14 Small Diameter, Thin and Heavy Wall + Thin Wall - Intermediate Diameter in Lengths to 40 in. for Reactor Applications . . CLASSIFICATION .... + : 42 . 2 *. WF6 CVD of Heavy-Wall Tübe Shell | 1 Process B . Process A Duplex Extrusion into Thin-Wall Shell Hot Plug Drawing Direct Deposition of Tubing Product on Mandrel 2.- 1 . 1 ..-. ..-": 1'indu' ii : Lina Ail!. :; ..1... . 1" 2 .1. 1 1 * * . ." - T- -. - .'. - " - .. - . :. . . - . :: : :'.t . 7 . . ܝܐ ܂ . ... .. ? .. T . .. ... . . . or *M 1.- . 2 .- .. '; : ' 2 t .. Als ?.. . ' - : , . -." ins! 1. 11 , *ST. G iá : ".. Y .:: . . . ''' :' . .! : 1: . "...! : .. :.: :. . : :. : CVD of Heavy-Wall Tribe Shell 1 . . . . . . - .. - Process B . . . . . : 1. * -1. ? .. ..i :-, -. Duplex Extrusion into Thin-Wall Shell .-.. : -D Hot Plug Drawing Direct Outside- Diameter Manera Deposition of Tubing Product on Mandau bitiminde eti I. . * Fig. 2. Basic Approaches to the Production of CVD Tubing. . . . : . . 3 . . 4 10 1. . !! . . . . 1 7 ni . " . . . . . . M . . + . .. 1 : S . . . -'- PT :,, . GY S . . Y . : . . . I. 1 H 2 T . , 1 . . i .1 Sii, . . . 1 .. . LT - ... 1 . . . .. . 11.- i. Wir .. - .T . . Prema . . " . . . s . . "iiii . . : : . 7 . .. . - 27 . 1 . . . . . . U . . . S . ' رخنه صممه منها مانند که من I ** N . Vi .. 11 1 . . 2. 1 ." . t': . . . 11 01 . , . .. 1 - . . - . . . . . . .". - Y .- TO . * . . ". A . 1: - .. .. - TE , TA . .. . - ... . I 1. . . . . . . . - . Historiens ...en onena :1:1. M r TTTTTTTTTTTTTTT . Simon. I . .......wien 4 ". ** OAK RIDGE NATIONAL LABORATOR li (b) 1 , " . ' .. i ' ,.. ...- ... . .: , . 7 : . ' . Extristan tule shello and Duplex billets used for Refisitory metals Photographs of (a) evo tube shell prin to extreem and (b) exploded neen of duplex extrun billet .. | 7g 3 .. . .,. . TW I T :: . ... . .. " . . . . .. ! ! S-a I. -. . : - - . . . . .1 ? . " . . . ..- - - - ... . . .. . . .. . .. ... . ?. . . ., .. . . 9 76 1 hy . . 1 . i ! .., 4 . . . . F 4 . . . .. S ...'.. 1..... ... * A * W !! ...: . . " . . . L . . . P' " - I! 4 1 + 14 Y ! 25 . 2 BOL TY in . " 11 2 . . - . !! . . t ' u . " . 24. ! M Uti . . .! tri . C " S . . in 73 * . .. Se .* . * 3 1' -*. . r . 1 . . 7 . 1 ". . 1. . . T . . . . . :, :' ... -. -... . . - -- 1 ... . Fig. 4, Photographs of Extruded Tungsten Tubing. On the right, the as-extruded shell is shown with the molybdenuna After the jacket material is removed by chemical dissolution, the tungsten tubing is as shown on the left. 4 .. ... - .. .. TWTTAYT Virth ... F .-- . R OITLE'TATIVE IJA -... N * s. T . . . -. i . :T - i . ..! i : - T . .' - • . 11. 1. - . . . T . ..kr . 21 . . . .. LIN - T. . .A -.'. .. ...: 1 . _ * " . 1 . 2 : nie? . * I 0 ! . . . . 11 . . C .. VA. . ***, . -0.035 INCHES XOOL 0 .. . . - .. . . .. . ST TES De MILLE Winter "" , der monditeenindo 1 i . Fig. . Microstructures of the As-Deposited-extruded-and-Drawn CVD Tungsten. (a) As deposited; (b) as extruded at 1700°C and 8:1 reduction: and (c) as drawn at 700°C (85% reduction). - - - - . . . . . . iS - ., V ST . * internet : ,'iii,, ... 1 a ; ; ovqman.. s ." .. .co memimi derdhen tarta im Swoon. TOYOTE, WAV pwysu Dia 0.035 INCHES 100X menimme mit dem 1 * T. b which was continue Readin Fig ücrostructures of Extruded and Drawn CVD Tungsten After Heat Treatment. (a) Partial recrystallization of CVD tungsten having . 0°C and heat treated for 0.3 hr at 1200°C. (b) Complete, recrystallization of CVD tungsten having been extruded at 1700 °C (8:1 re- duction) and heat treated for 1 hr at 2000°C.. NA . . . . . in . . TALAJ MA D. . STARTING MATERIAL Tungsten Oxide Tungstic Acid Ammonium Paratungstate -. Reacted with Flourine to Form WF. h ore Hydre Ore Hydrogen-Reduced to Powder FA $ . Direct CVD Deposition CVD Tube Shell Arc-Cast or Powder- Metallurgy Billet 1 (Heavy Wall) Tube Shell Extrusion Sheet Bar Extrusion 16 TE (Thin Wall) Hot Plug Draw Warm Mandrel Draw Multiple Steps Rolling into Sheet . . 1 . SALTY rii '. Form Sheet into Tube Shape and Weld :- : . ! . ** Warm Mandrel Drawing Single Steps Final Tubing Product 7 .. 14 . . . . 22 . ) . 1 . 11 STARTING MATERIAL Tungsten Oxide Tungstic Acid. Armonium Paratungstate . Reacted with to Form WF6 Tore Hydrogen Reduced to Powder . : ::::: CVD Tube Direct CVDI Deposition Arc-Cast or Powder. Metallurgy Billet Shell Atawy wait) ' ' Tube Shell Extrusion Sheet Bar Extrusion AAN hin woll) Hot Plug Draw Rolling into Sheet . Warta Mandrel Draw Multiple Steps Form Sheet into Tube Snape and Weld .! . A . . Warra Mandrel Drawing. Single Steps .. : V Final Tubing Product N1, ! Sar Fabrication ROUTES for Production of Tungsten Tubina NA! .. ..... skraid . . para promotion to !. ... 11 ! 1 ALA END - • . 2 DATE FILMED 8 / 16 /67 ; 1 . .