Accession Number : AD0011576


Title :   ALLOYS FOR HIGH-TEMPERATURE SERVICE


Descriptive Note : Final rept


Corporate Author : BATTELLE MEMORIAL INST COLUMBUS OH


Personal Author(s) : Beck, R L ; Fletcher, E E ; Elses, A R ; Westerman, A B ; Manning, G K


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/011576.pdf


Report Date : 30 Apr 1952


Pagination or Media Count : 36


Abstract : A metallographic and x-ray diffraction study of the Co-Cr binary diagram and a study of the effect of ternary additions were undertaken for a structural analysis of Vitallium alloys. The following sluggish transformation reactions were indicated: (1) Cr and Mo raised the alpha-beta transformation temperature in the Co-Cr systems; (2) N, Fe, and Ni markedly lowered the temperature; and (3) W had little effect. All the ternary additives raised the alpha Co2Cr3 precipitation temperature; the compound precipitated at a low Cr concentration in a spheroid or platelet form. The upper limit (1000 deg. C) of the alpha-beta transformation temperature of Stellite no. 21 was lowered by Ni and raised by C and Mo. Minor phases in Stellite included Co2Cr3, M23C6, M6C, and Cr7C3. Creep-rupture tests on Co-Cr alloys with and without N at 780 deg., 915 deg., and 1000 deg. C indicated that: (1) an increase in the Cr, C, or Ni content increased the strength; (2) alpha and beta phases had about the same strength at elevated temperatures; (3) some alloys had lower creep rates at high stresses than at lower stresses; and (4) an increase in the prestress at a given testing temperature lowered the creep rate. Time-deformation curves probably represented a normal tendency toward creep combined with a contraction tendency resulting from the precipitation of submicroscopic particles. Stellite alloys, subjected to creep-rupture tests at 816 deg. C, were stronger in the as-cast condition than after homogenizing or homogenizing and aging. Minor changes in C, Ni, or Mo had little effect on the aging characteristics. No relationship was found between the rupture strength and hot-hardness.


Descriptors :   *REFRACTORY METAL ALLOYS , *HEAT RESISTANT ALLOYS , STRESSES , AGING(MATERIALS) , HIGH TEMPERATURE , STRUCTURAL ANALYSIS , X RAY DIFFRACTION , RATES , RUPTURE , PHASE , PRECIPITATION , PARTICLES , DIFFRACTION , LIMITATIONS , STRENGTH(GENERAL) , CREEP , ADDITIVES , TERNARY COMPOUNDS , LOW RATE , ADDITION , TRANSFORMATIONS , METALLOGRAPHY , CASTINGS , CREEP TESTS


Subject Categories : Metallurgy and Metallography


Distribution Statement : APPROVED FOR PUBLIC RELEASE