OXIDATION OF NICKEL- AND COBALT-BASE …

1 DMIC Report 214 March 1, 1965 OXIDATION OF nickel - AND COBALT-BASESUPERALLOYSWAY 11'HARD COPY $. $. (6-_"oDEFENSE METALS INFORMATION CENTERB attelle Memorial InstituteColumbus, Ohio 43201owThe Defense Metals Information Center was established atBattelle Memorial Institute at the request of the Office of theDirector of Defense Research and Engin4ering to provide Govern-ment contractors and their suppliers technical assistance andinformation on titanium, beryllium, magnesium, aluminum, refrac-tory metals, high-strength alloys for high-tomperature service.)

2 Corrosion- and OXIDATION -resistant coatings, and systems. Its functions, under the direction of the Office ofthe Director of Defense Research and Engineering, are as follows:1. To collect, store, and disseminate technical In-formation on the current status of research anddevelopment of the above To supplement established Service activities inproviding technical advisory services to , melters, and fabricators of the abovematerials, and to designers and fabricators ofmilitary equipment containing those To assist the Government agencies in developing technical data requirodforpreparation of specifications for the above On assignment, to conduct surveys.

3 Or laboratoryresearch isveatigations, mainly of a short-rangenature, as required, to ascertain causes of trou-bles encountered by fabricators, or to fill minorgaps in established research No. AF 33(615).lltProject No, 897 SRoger J. RunckDirectorSWR Ut01o in th" " re ort " "m. tr-mJAB ne i MY b0 4 b een S xte ul, uotathe o iriini tL autbor MD d th e ari n g ag em .-tr Patent quest ioASLpear to be ..towa e'arh is advised bttOre making u86 of the material. and where cpy" J m aVtJLerilB it E8,d.

4 Fern OM .O b o t,,-further publioatior.,OIt Oo" tt t13 PIES AVELILE RNM |.,CLEARINGHOUSE FOR FEDERAL SCIENTIFIC AND TECHNICAL INFORMATION, CFS'iINPUT SECTION IN REPRODUCTION QUALITY OF TECHNICAL ABSTRACT BULLETINDOCUMENTS, DEFENSE DOCUMENTATION CENTER (ODOC)I. AVAILABLE ONLY FOR REFERENCE USE AT DOC FIELD IS NOT AVAILABLE FOR PUBLIC 2. AVAILABLE COPY WILL NOT PERMIT FULLY LEGIBLE WILL BE MADE IF REQUESTED BY USERS OF COPY IS AVAILABLE FOR PUBLIC COPY IS NOT AVAILABLE FOR PUBLIC 3. LIMITED NUMBER OF COPIES CONTAINING COLOR OTHER THAN BLACKAND WHITE ARE AVAILABLE UNTIL STOCK IS EXHAUSTED.

5 REPRODUCTIONSWILL BE MADE IN BLACK AND WHITE DATE PROCESSED:PROCESSOR:IIIDMIC Report 214 March 1, 1965 OXIDATION OF NICKEL- AND COBALT-BASESUPERALLOYSbyC. H. Lund and H. J. WagnertoOFFICE OF THE DIRECTOR OF DEFENSERESEARCH AND ENGINEERINGDEFENSE METALS INFORMATION CENTERB attelle Memorial InstituteColumbus, Ohio 43201 The new high-strength NICKEL- base alloys with chromiumcontents of about 10 percent do not have adequate oxidationresistance over their utef-l temperature range and requireprotective which promote OXIDATION resistance in super-alloys.

6 Are chromium, silicon, aluminum, and several ofthe rare earths, especially adversely affects OXIDATION resistance; so dotitAnium, molybdenum, and tungsten if over 0. 5 can he beneficial if it produces a uniform ad-herent protective surface film, or if it produces a filmused to alter surface properties, such as to OF CONTENTSPageSUMMARY .. iINTRODUCTION ..1 FUNDAMENTALS OF THE OXIDATION OF Ni-Cr AND Co-Cr ALLO7S .. 1 GENERAL SURFACE 3 Experimental Methods .. 4 OXIDATION of ..4 INTERGRANULAR OXIDATION .

7 16 Alloy Depl-tion Effects .. 21 OTHER SUBSURFACE OXIDATION .. 22 EFFECT OF STRESS .. 23 REFERENCES .. 25 APPENDIXALLOY INDEX AND COMPOSITIONS .. A-IOXIDATION OF nickel - A14b COBALT-BASE SUPERALLOYSbyC. H. Lund* and H. J. Wagner**SUMMARYThe superalloys are OXIDATION resistant but all Intergranular OXIDATION is preceded by alloywill oxidize at high temperatures when oxygen is depletion ahead of the advancing oxide front. Thepresent. The rate of OXIDATION will depend upon compositional gradient that is produced can act asmany factors including alloy composition, tem- the driving force for continued metal-ion , oxygen concentration, diffusion rates, The depleted zone also is weaker than the basicetc.

8 Alloys designed for maximum strength will alloy, particularly in precipitation-hardenablenot have maximum OXIDATION resistance. There- NICKEL- base alloys where chromium, aluminum,fore, the application of superalloys is a corn- and titanium are preferentially oxidized because ofpromise between strength and OXIDATION consider- their relatively high affinity for oxygen. Loss ofations. When maximum strength and OXIDATION titanium and aluminum content is particularlyresistance are both desired, protective coatings detrimental to strength conditions of atmosphere or are very complex nickel - or surface can result in subsurface OXIDATION notcobalt-base alloys containing closely controlled usually found in superalloys.

9 For example, in-amounts of several elements. Each of these ele- ternal preferential OXIDATION of chromium ratherments can participate in the oxide formation dur- than nickel might occur in atmospheres that areing high-temperature exposure, their participation oxidizing to chromium and reducing to nickel , orbeing regulated by activation energy, diffusion, internal OXIDATION might take place under a sur-and heat of formation of the oxides, face that has been previously carburized. Pa-rameters for internal OXIDATION are not clearlyGeneral surface OXIDATION is the formation of oxide layer of relatively uniform thickness onthe surface of the alloy.

10 Light surface OXIDATION Stress has an effect on the rate of often not objectionable and may even be bene- It appears that OXIDATION proceeds at a constantficial. Intergranular OXIDATION , on the other hand, rate with increasing stress until a "critical"can be a serious problem on thin sections or wire stress level is reached at which OXIDATION pro-when present in only small amounts. The pene- ceeds much more rapidly. Stress also producestration of the oxide front not only reduces the ef- spalling of even the tightly adherent oxides cffective cross section, but it can act as a notch to most superalloys when sufficient shear is pro-reduce fatigue resistance.