Scholars' Mine Masters Theses Student Theses and Dissertations 1947 A study of certain properties of a cobalt-chromium-manganese alloy for high temperature service Robert Lewis Ray Follow this and additional works at: https://scholarsmine.mst.edu/masters_theses Part of the Metallurgy Commons Department: Recommended Citation Ray, Robert Lewis, "A study of certain properties of a cobalt-chromium-manganese alloy for high temperature service" (1947). Masters Theses. 4907. https://scholarsmine.mst.edu/masters_theses/4907 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. A STUDY OF CERTAIN PROPERTIJ:f.S OF A COBA.LT-CHROMIUM- [ANGANESE~ ALLOY FOR HIGH TEMPERATURE SER,VICE By ROBE~RT LEVi I8 RAY A THESIS submitted to the faculty of the SCHOOL OF MINES AND ETALLURGY. OF THE UNIVERSITY OF ISSOURI in partial fulfillment of the work required for the Degree of MASTER OF SCIENCE, METALLURGICAL ENGINEERING Rolla, Missouri 1947 Approved by ~'--...........~~ _ A. • Schlechten Chairman, Dep~rtment of Metallurgical Engineering and Mineral Dressing 1. Ackno 'ledgment The author wishes to thank the Missouri School of Mines and Meta.llurgy for the op ortunity of the use of equipment and facilities necessary for the pr·oduction Q·f this investigation, Dr. A•• Schlechten and Prof. C.Y. Clayton for their helpful counsel during the course of the ·ork. II Table of Conte:nts page Ackno ledgment I List of Illustrations III List of Tables IV Introduction 1 Revie of Literature 4 Preparation of the Alloys 9 The Aging Properties of the Co-Cr-Mn Alloy After Solution Treatment, Followed by Swaging 12 The Aging Properties of the Co-Cr-Mn Alloy After Swaging, Followed by Solution Treatment 20 The Aging Properties of the Cast Co-Cr-Mn Alloy 24 A Study of the Hardness of the Microconstituents of the Co-Cr-Mn Alloy by the Use of the Tukon Microhardness Tester 27 The Thermal Expansion Properties of the Co-Cr-Mn Alloy 34 Oxidation Resistance of the Co-Cr-Mn Alloy 37 Ductility of the Co-Cr-Mn Alloy 37 Conclusions 38 Summary 41 Bibliography 42 Index 43 III List of Illustrations Page Fig. 1 Ternary Diagram Sho ing Ductile Range of Co-Cr-Mn Alloys 5 Fig. 2 Graph Showing Hardness Changes With In­ creasing Aging Temperatures for Times of One Hr., Co-Cr-Mn Alloy, Solution Treat­ ed and Swaged 14 Fig. 3 Photomicrograph Showing Solution Treated and S aged Co-Cr-Mn Alloy 17 Figs. 4-5 Photomicrographs Shoo ing Co-Cr-Mn Alloy, Solution Treated, Swaged and Aged at 15000 F for One Hr. 18 Photomicrographs Shoing Co-Cr-Mn Alloy, Solution Treated, S aged and Aged at 16000F ror One Hr. 19 Fig. 8 Photomicrograph Shoo ing Co-Cr-Mn Alloy, Solution Treated, Swaged and Aged at 19000 F for One Hr. 19 Fig. 9 Photomicrograph Showing Co-Cr-Mn Alloy, As Cast 21 Fig. 10 Photomicrograph Showing Co-Cr-Mn Alloy, Swaged and solution Treated 21 Fig. 11 Photomicrograph Sho.ing co-Cr-Mn Alloy, S aged Solution Treated, and Aged at 170QoF for One Hr. 21 Fig. 12 Graph Showing Hardness Changes With In­ creasing Aging Temperatures for Times of One Hr., Co-Cr-Mn Alloy, Swaged and Solu­ tion Treated 22 Fig. 13 Graph Sho ing Hardness Ch~nges With In­ creasing Aging Temperatures for Times of One Hr., Co-Cr-Mn Alloy, As Cast 25 Fig. 14 Photomicrograph Showing Co-Cr-Mn As Cast and Aged 2000~ for One Hr. 26 Figs. 15-19 Photomicrographs Shoing Tukon Indenta­ tions and Corresponding Knoop Hardness Numbers in Various Structures 28-30 IV List of Tables Page Table I Typical Analyses of Alloys for High Temperature Service 2 Table II Analyses of Alloys Meeting Requirements in 1200OF-1500oF Range 8 Table III The Age Hardening of the Co-Cr-Mn Alloy After Various Heat Treatments 13 Table IV Comparison of Knoop Microhardnesses With Standard Rockwell "e tt Hardnesses of the Co-Cr-Mn Alloy 31 1. Introduction The vast amount of attention that has been given to the development of high-temperature service alloys since about 1940 has resulted in the production of numerous compositions for many elevated temperature applications. Particula.. rly in the aircraft industry, with the jet engine, and the power industry, with the gas turbine, have these applications been most demanding. War research has develop­ ed a large number of high-temperature service alloys, many of which are in use today, and the alloy ingredients vary widely. Some of the typical compositions are shown in (1) Table 1. (1) H.A. Knight: Super Alloys for High-Temperature Service, Materials and Methods, v. 23 n. 6, June, 1946, p. 1557­ 1563. From these compositions, and the applications noted, it may readily be seen that there is no one alloy, or one system of alloys which has been developed that has satisfied any extensive portion of the users' needs. However, all of these compositions have Co, Cr, and Ni in some proportions, plus various other alloy additions. An investigation by • Dr. B.S. Dean, (2) who considered various alloy compositions (2) R.S. Dean: High-Temperature Alloy Compositions, Corre­ snonnence, O,ctober, 1.946. for high temperature service, has shown that the more basic requirements of' suc'h hi,gh-temp,eratur,e alloys are met in the TABLE I Typical Analyses of Alloys for High Temperature Service Alloy Designation C Mn 81 Cr Ni Co Mo W Cb Fe Maker Applications L,ow Carbon .15 1.00 .50 20.0 20.0 20.0 3.0 2.0 1.0 xx Haynes Gas Turbine Blades Low Carbon .15 1.50 .50 16.0 15.0 13.0 3.0 2.0 1.0 xx Haynes Experimental 8-816 .40 .63 .63 20.0 20.0 44.0 4.0 4.0 4.0 4.0 Alleg'ny Buckets Ludlum Hast,elloy B .05 .60 .25 xx 65.0 29.0 xx xx xx 4.5 Raynes Buckets V1tal11um .30 .30 .25 27.0 2.0 64.0 5.0 xx xx 2.0 Austenal Buckets, Jet Buckets Liners, Tail Cones Vanadium Corp xx xx xx 25.0 20.0 20.0 xx 15.0 xx xx (.60 B) NDRC Research xx xx xx 35.0 30.0 50.0 xx 25.0 xx xx X-40 .45 xx xx 26.5 11.0 54.5 xx 7.2 xx .60 G.E. Gas turbine, Jet engine Bl8.des Hastelloy C .15 1.0 1.0 16.0 15.0 xx 17.0 5.0 xx 5.5 (1.0 AI) Haynes Stellite Develop. M • 3. Co-Cr system of about 60% Co-40% Cr. This system having the distinct inherent disadva.ntage of poor cold-working properties, Dr. Dean found it advantageous to add 25% man­ ganese, thereby producing a ductile alloy. There being no investigations supplementing the work by Dr. Dean, the folIo ing investigation as undertaken to further determine the properties of the Co-Cr-Mn alloy by observing: The changes in hardness with heat-treatment; the microstructures of the cast~ worked, and heat-treated alloy; the thermal expansion from room temperature to maximum service tempera­ ture; the oxidation resistance at service temperatures; and the cold ductility by swaging. In order to obtain the true basic properties of this alloy, metals of high purity were used as alloy constituents. 4. Review of Literature Constitution of the Co-Cr-Mn System No information in the literature was found concerning the constitution of the ternary Co-Cr-Mn system. Binary systems of Co-Cr and Co-Mn constitutions have been presented by M. Hansen,(3) but the Co-Mn system was not complete belo (3) M. Hansen: Aufbau dar Zweistofflegierungen, Berlin, Springer, 1936, p. 493, p. 477. the liquidus temperatures. The Co-Cr system shows a two­ phase structure for the 60Co-40Cr alloy. This structure, as­ cast and homogenized, has been identified by R.D. Moeller(4) (4) R.D. Moeller: A Study of the 60Co-40Cr Alloy for High­ Temperature Service, Thesis, Missouri School of Kines and Metallurgy, August, 1947. in a micostructural study which showed soft material through­ out the entire microsectlon. According to the Co-Mn diagram available, the binary alloy constitution could not be ascer­ ta,ined, the data being incomplete. Ductility The ~ange of' compositions fo,r ductile alloys in the Co-Cr-Mn system, as determined by R.S. Dean is shown in Figure 1. From. this figure, it may be observed that ductile a110ys are believed to exist in the range between the amounts of slightly less than 15, and slightly more than 25% added Mn. The most ductile of the alloys produced contained 25% added Mn, according to Dr. De'an. Ho ever', th,e upper limit 5. F ~i TERNARY SHO'~ING DUCTILE RA GE OF Co-CR-MN AL.LOY'S ~o ....-..~--....------...... ~ ~& 2.6 .....--.......--.Jpo~~~.......------A---¥-~ ~~ f{\ 2.ur----A-------ilP---~~~~~ * t5 6. of the ductility range as sho~n in Figure 1 does not include sufficient experimental data to verify the ductile-brittle boundary, since no brittle alloys are shown above 20% Mn. The ductility comparisons were made by swaging 5/8" diameter bars to 1/4ft diameter bars without intermediate anneals. W.O. Binder(5) has reported that a brittle intermetal- (5) ~ .0. Binder, Correspondence, December, 1946. lie compound exists at 47% Cr, 53% Co, and it as consequent­ ly proposed that the Mn might act ,as Cr in the Co-Cr system, thereby promoting the formation of the brittle constituent.