Pete Kantzos - Academia.edu (original) (raw)

Papers by Pete Kantzos

Mechanical properties from an advanced, nickel-base superalloy disk, with a dual grain structure ... more Mechanical properties from an advanced, nickel-base superalloy disk, with a dual grain structure consisting of a fine grain bore and coarse grain rim, were evaluated. The dual grain structure was produced using NASA's low cost Dual Microstructure Heat Treatment (DMHT) process. The results showed the DMHT disk to have a high strength, fatigue resistant bore comparable to a subsolvus (fine grain) heat treated disk, and a creep resistant rim comparable to a supersolvus (coarse grain) heat treated disk. Additional work on subsolvus solutioning before or after the DMHT conversion appears to be a viable avenue for further improvement in disk properties.

The grain size-temperature response was measured for a series of experimental disk superalloys. T... more The grain size-temperature response was measured for a series of experimental disk superalloys. The responses were compared and related to the chemistries of these alloys.

Timothy P. Gabb and John GaydaGlenn Research Center, Cleveland, OhioPete T. KantzosOhio Aerospace... more Timothy P. Gabb and John GaydaGlenn Research Center, Cleveland, OhioPete T. KantzosOhio Aerospace Institute, Brook Park, OhioTiffany BilesPurdue University, West Lafayette, IndianaWilliam KonkelWyman-Gordon Forgings, Houston, TexasPrepared for the2001 Fall Meetingsponsored by The Minerals, Metals, and Materials SocietyIndianapolis, Indiana, November 4--8, 2001National Aeronautics andSpace AdministrationGlenn Research Center

International Journal of Fatigue, 2021

Crack initiation, crack coalescence and small crack growth behavior were monitored for over 400 s... more Crack initiation, crack coalescence and small crack growth behavior were monitored for over 400 seeded inclusions during interrupted low cycle fatigue testing conducted on the P/M Udimet 720 nickel disk alloy at 650 °C. Two types of seeded alumina inclusions with average sizes of 54 µm and 122 µm were used in the study performed at varying loading conditions resulting in LCF lives ranging from 2,000 cycles to over 1,000,000 cycles. The fatigue behavior was subcategorized into four groups. Visual maps detailing inclusion size/cycle history were developed. The effect of surface residual stresses on the fatigue life was also investigated.

Mechanical, Thermal and Environmental Testing and Performance of Ceramic Composites and Components

Abstract: Creep-rupture and fatigue tests were conducted to identify the failure modes and degrad... more Abstract: Creep-rupture and fatigue tests were conducted to identify the failure modes and degradation mechanisms of a [0/90] carbon fiber reinforced silicon carbide (C/SiC) composite at 550 and 650 C. When compared on a maximum stress versus time to failure ...

Superalloys 2004 (Tenth International Symposium), 2004

A study was performed to determine the variables which influence hold time crack growth resistanc... more A study was performed to determine the variables which influence hold time crack growth resistance of Alloy 10, a new powder metallurgy (P/M) superalloy. In a well controlled study, both the effect of compositional changes and variation in heat treatments were investigated. The results indicate that significant changes in the alloy's niobium, tantalum and cobalt content did not have an appreciable effect on hold time crack growth resistance. In contrast to the composition study, the heat treatments evaluated produced up to an order of magnitude changes in the crack growth resistance. Quantitative image analysis was performed to analyze the microstructural features produced by each heat treatment. It was found that the cooling precipitate size distribution is closely related to the measured hold time crack growth behavior. The larger the mean size of the cooling precipitates, the better is the resistance to hold time crack growth. It is proposed that the size and distribution of the precipitates might play an important role in determining the extent of crack tip relaxation which occurs through creep-type processes. The differences in the stress relaxation rate influence the crack driving forces and thus crack growth resistance.

Superalloys 2004 (Tenth International Symposium), 2004

Non-metallic inclusions, which are inherent to the powder metallurgy process, can have a deleteri... more Non-metallic inclusions, which are inherent to the powder metallurgy process, can have a deleterious effect on the fatigue life of turbine disks. An artificial seeding study, where both the size and occurrence rate of the ceramic seeds were well controlled and characterized, was employed as a means of studying the effects of powder dirtiness on fatigue life. Various methods of quantifying cleanliness; quantitative metallography, quantitative fractography, and heavy liquid separation, were evaluated and compared. In addition, extensive metallographic characterization of seeded extrusions and forgings was performed in order to quantify the effect of mechanical processing on inclusion morphology.

Superalloys 2012, 2012

Mechanical property requirements vary with location in nickelbased superalloy disks. In order to ... more Mechanical property requirements vary with location in nickelbased superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 °C and 704 °C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

Materials Science and Engineering: A, 2008

The fatigue lives of modern powder metallurgy disk alloys can be reduced by over an order of magn... more The fatigue lives of modern powder metallurgy disk alloys can be reduced by over an order of magnitude by surface cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet ® 720. Multiple strain-controlled fatigue tests were then performed on machined specimens at 427 and 650 °C in peened and unpeened conditions. Analyses were performed to compare the low cycle fatigue lives and failure initiation sites as a function of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. The inclusions could reduce fatigue life by up to 100X. Large inclusions had the greatest effect on life in tests at low strain ranges and high strain ratios. Shot peening can be used to improve life in these conditions by reducing the most severe effects of inclusions.

Journal of Failure Analysis and Prevention, 2007

ABSTRACT Increasing service temperatures of gas turbine engines can improve performance and effic... more ABSTRACT Increasing service temperatures of gas turbine engines can improve performance and efficiency. Therefore, advanced alloys are being considered for higher-temperature applications than previously encountered. To support these higher-temperature applications, failure mode assessments on specimens tested in laboratory test machines can help in understanding prospective failure scenarios. The effects of temperature on tensile, creep, low-cycle fatigue, and fatigue crack growth failure modes were evaluated for an advanced powder metallurgy disk superalloy ME3. Conventional tests were performed at temperatures up to 815°C on specimens extracted from supersolvus heat treated disks. The failure modes were compared with increasing temperature for each test type. Fractographic evaluations indicate the failure modes were shifted by increasing temperature, and eventually became environment-assisted, surface crack initiated failures.

International Journal of Fatigue, 2011

Level of Review: This material has been technically reviewed by technical management.

In the absence of extrinsic surface damage, the fatigue life of metals is often dictated by the d... more In the absence of extrinsic surface damage, the fatigue life of metals is often dictated by the distribution of intrinsic defects. In powder metallurgy (PM) alloys, relatively large defects occur rarely enough that a typical characterization with a limited number of smallvolume fatigue test specimens will not adequately sample inclusion-initiated damage. Counterintuitively, inclusion-initiated failure has a greater impact on the distribution in PM alloy fatigue lives because they tend to have fewer defects than their cast and wrought counterparts. Although the relative paucity of defects in PM alloys leads to higher mean fatigue lives, the distribution in observed lives tends to be broader. In order to study this important failure initiation mechanism without expending an inordinate number of specimens, a study was undertaken at the NASA Glenn Research Center where known populations of artificial inclusions (seeds) were introduced to production powder. Map of a low-cycle fatigue (LCF) specimen surface showing the relative sizes of observed surface inclusions and crack lengths observed at intervals during interrupted fatigue testing; da/dN, crack growth rate. Long description. Illustration of surface specimen and graph of axial location in inches versus angle in degrees for C-L17 interruptions from 250 to 2402 cycles.

A low solvus, high refractory (LSHR) powder metallurgy disk alloy was recently designed using exp... more A low solvus, high refractory (LSHR) powder metallurgy disk alloy was recently designed using experimental screening and statistical modeling of composition and processing variables on sub-scale disks to have versatile processing-property capabilities for advanced disk applications. The objective of the present study was to produce a scaled-up disk and apply varied heat treat processes to enable fullscale demonstration of LSHR properties. Scaled-up disks were produced, heat treated, sectioned, and then machined into specimens for mechanical testing. Results indicate the LSHR alloy can be processed to produce fine and coarse grain microstructures with differing combinations of strength and time-dependent mechanical properties, for application at temperatures exceeding 1300 °F.

The objective of this study was to assess the relaxation of stresses at increasing temperatures i... more The objective of this study was to assess the relaxation of stresses at increasing temperatures in several PM superalloy disks. The effects of temperature, time, and plasticity were examined.

Surface enhancement methods induce a layer of beneficial residual compressive stress to improve t... more Surface enhancement methods induce a layer of beneficial residual compressive stress to improve the impact (FOD) resistance and fatigue life of metallic materials. A traditional method of surface enhancement often used is shot peening, in which small steel spheres are repeatedly impinged on metallic surfaces. Shot peening is inexpensive and widely used, but the plastic deformation of 20 to 40 percent imparted by the impacts can be harmful. This plastic deformation can damage the microstructure, severely limiting the ductility and durability of the material near the surface. It has also been shown to promote accelerated relaxation of the beneficial compressive residual stresses at elevated temperatures. Lowplasticity burnishing (LPB) is being developed as an improved method for the surface enhancement of metallic materials.

The successful development of an advanced powder metallurgy disk alloy, ME3, was initiated in the... more The successful development of an advanced powder metallurgy disk alloy, ME3, was initiated in the NASA High Speed Research/Enabling Propulsion Materials (HSR/EPM) Compressor/Turbine Disk program in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. This alloy was designed using statistical screening and optimization of composition and processing variables to have extended durability at 1200°F in large disks. Disks of this alloy were produced at the conclusion of the program using a realistic scaled-up disk shape and processing to enable demonstration of these properties. The objective of the Ultra-Efficient Engine Technologies disk program was to assess the mechanical properties of these ME3 disks as functions of temperature, in order to estimate the maximum temperature capabilities of this advanced alloy. These disks were sectioned, machined into specimens, and extensively tested. Additional sub-scale disks and blanks were processed and selectively tested to explore the effects of several processing variations on mechanical properties. Results indicate the baseline ME3 alloy and process can produce 1300-1350°F temperature capabilities, dependent on detailed disk and engine design property requirements.

Mechanical properties from an advanced, nickel-base superalloy disk, with a dual grain structure ... more Mechanical properties from an advanced, nickel-base superalloy disk, with a dual grain structure consisting of a fine grain bore and coarse grain rim, were evaluated. The dual grain structure was produced using NASA's low cost Dual Microstructure Heat Treatment (DMHT) process. The results showed the DMHT disk to have a high strength, fatigue resistant bore comparable to a subsolvus (fine grain) heat treated disk, and a creep resistant rim comparable to a supersolvus (coarse grain) heat treated disk. Additional work on subsolvus solutioning before or after the DMHT conversion appears to be a viable avenue for further improvement in disk properties.

The grain size-temperature response was measured for a series of experimental disk superalloys. T... more The grain size-temperature response was measured for a series of experimental disk superalloys. The responses were compared and related to the chemistries of these alloys.

Timothy P. Gabb and John GaydaGlenn Research Center, Cleveland, OhioPete T. KantzosOhio Aerospace... more Timothy P. Gabb and John GaydaGlenn Research Center, Cleveland, OhioPete T. KantzosOhio Aerospace Institute, Brook Park, OhioTiffany BilesPurdue University, West Lafayette, IndianaWilliam KonkelWyman-Gordon Forgings, Houston, TexasPrepared for the2001 Fall Meetingsponsored by The Minerals, Metals, and Materials SocietyIndianapolis, Indiana, November 4--8, 2001National Aeronautics andSpace AdministrationGlenn Research Center

International Journal of Fatigue, 2021

Crack initiation, crack coalescence and small crack growth behavior were monitored for over 400 s... more Crack initiation, crack coalescence and small crack growth behavior were monitored for over 400 seeded inclusions during interrupted low cycle fatigue testing conducted on the P/M Udimet 720 nickel disk alloy at 650 °C. Two types of seeded alumina inclusions with average sizes of 54 µm and 122 µm were used in the study performed at varying loading conditions resulting in LCF lives ranging from 2,000 cycles to over 1,000,000 cycles. The fatigue behavior was subcategorized into four groups. Visual maps detailing inclusion size/cycle history were developed. The effect of surface residual stresses on the fatigue life was also investigated.

Mechanical, Thermal and Environmental Testing and Performance of Ceramic Composites and Components

Abstract: Creep-rupture and fatigue tests were conducted to identify the failure modes and degrad... more Abstract: Creep-rupture and fatigue tests were conducted to identify the failure modes and degradation mechanisms of a [0/90] carbon fiber reinforced silicon carbide (C/SiC) composite at 550 and 650 C. When compared on a maximum stress versus time to failure ...

Superalloys 2004 (Tenth International Symposium), 2004

A study was performed to determine the variables which influence hold time crack growth resistanc... more A study was performed to determine the variables which influence hold time crack growth resistance of Alloy 10, a new powder metallurgy (P/M) superalloy. In a well controlled study, both the effect of compositional changes and variation in heat treatments were investigated. The results indicate that significant changes in the alloy's niobium, tantalum and cobalt content did not have an appreciable effect on hold time crack growth resistance. In contrast to the composition study, the heat treatments evaluated produced up to an order of magnitude changes in the crack growth resistance. Quantitative image analysis was performed to analyze the microstructural features produced by each heat treatment. It was found that the cooling precipitate size distribution is closely related to the measured hold time crack growth behavior. The larger the mean size of the cooling precipitates, the better is the resistance to hold time crack growth. It is proposed that the size and distribution of the precipitates might play an important role in determining the extent of crack tip relaxation which occurs through creep-type processes. The differences in the stress relaxation rate influence the crack driving forces and thus crack growth resistance.

Superalloys 2004 (Tenth International Symposium), 2004

Non-metallic inclusions, which are inherent to the powder metallurgy process, can have a deleteri... more Non-metallic inclusions, which are inherent to the powder metallurgy process, can have a deleterious effect on the fatigue life of turbine disks. An artificial seeding study, where both the size and occurrence rate of the ceramic seeds were well controlled and characterized, was employed as a means of studying the effects of powder dirtiness on fatigue life. Various methods of quantifying cleanliness; quantitative metallography, quantitative fractography, and heavy liquid separation, were evaluated and compared. In addition, extensive metallographic characterization of seeded extrusions and forgings was performed in order to quantify the effect of mechanical processing on inclusion morphology.

Superalloys 2012, 2012

Mechanical property requirements vary with location in nickelbased superalloy disks. In order to ... more Mechanical property requirements vary with location in nickelbased superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 °C and 704 °C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

Materials Science and Engineering: A, 2008

The fatigue lives of modern powder metallurgy disk alloys can be reduced by over an order of magn... more The fatigue lives of modern powder metallurgy disk alloys can be reduced by over an order of magnitude by surface cracking at inherent non-metallic inclusions. The objective of this work was to study the effectiveness of shot peening in suppressing LCF crack initiation and growth at surface nonmetallic inclusions. Inclusions were carefully introduced at elevated levels during powder metallurgy processing of the nickel-base disk superalloy Udimet ® 720. Multiple strain-controlled fatigue tests were then performed on machined specimens at 427 and 650 °C in peened and unpeened conditions. Analyses were performed to compare the low cycle fatigue lives and failure initiation sites as a function of inclusion content, shot peening, and fatigue conditions. A large majority of the failures in as-machined specimens with introduced inclusions occurred at cracks initiating from inclusions intersecting the specimen surface. The inclusions could reduce fatigue life by up to 100X. Large inclusions had the greatest effect on life in tests at low strain ranges and high strain ratios. Shot peening can be used to improve life in these conditions by reducing the most severe effects of inclusions.

Journal of Failure Analysis and Prevention, 2007

ABSTRACT Increasing service temperatures of gas turbine engines can improve performance and effic... more ABSTRACT Increasing service temperatures of gas turbine engines can improve performance and efficiency. Therefore, advanced alloys are being considered for higher-temperature applications than previously encountered. To support these higher-temperature applications, failure mode assessments on specimens tested in laboratory test machines can help in understanding prospective failure scenarios. The effects of temperature on tensile, creep, low-cycle fatigue, and fatigue crack growth failure modes were evaluated for an advanced powder metallurgy disk superalloy ME3. Conventional tests were performed at temperatures up to 815°C on specimens extracted from supersolvus heat treated disks. The failure modes were compared with increasing temperature for each test type. Fractographic evaluations indicate the failure modes were shifted by increasing temperature, and eventually became environment-assisted, surface crack initiated failures.

International Journal of Fatigue, 2011

Level of Review: This material has been technically reviewed by technical management.

In the absence of extrinsic surface damage, the fatigue life of metals is often dictated by the d... more In the absence of extrinsic surface damage, the fatigue life of metals is often dictated by the distribution of intrinsic defects. In powder metallurgy (PM) alloys, relatively large defects occur rarely enough that a typical characterization with a limited number of smallvolume fatigue test specimens will not adequately sample inclusion-initiated damage. Counterintuitively, inclusion-initiated failure has a greater impact on the distribution in PM alloy fatigue lives because they tend to have fewer defects than their cast and wrought counterparts. Although the relative paucity of defects in PM alloys leads to higher mean fatigue lives, the distribution in observed lives tends to be broader. In order to study this important failure initiation mechanism without expending an inordinate number of specimens, a study was undertaken at the NASA Glenn Research Center where known populations of artificial inclusions (seeds) were introduced to production powder. Map of a low-cycle fatigue (LCF) specimen surface showing the relative sizes of observed surface inclusions and crack lengths observed at intervals during interrupted fatigue testing; da/dN, crack growth rate. Long description. Illustration of surface specimen and graph of axial location in inches versus angle in degrees for C-L17 interruptions from 250 to 2402 cycles.

A low solvus, high refractory (LSHR) powder metallurgy disk alloy was recently designed using exp... more A low solvus, high refractory (LSHR) powder metallurgy disk alloy was recently designed using experimental screening and statistical modeling of composition and processing variables on sub-scale disks to have versatile processing-property capabilities for advanced disk applications. The objective of the present study was to produce a scaled-up disk and apply varied heat treat processes to enable fullscale demonstration of LSHR properties. Scaled-up disks were produced, heat treated, sectioned, and then machined into specimens for mechanical testing. Results indicate the LSHR alloy can be processed to produce fine and coarse grain microstructures with differing combinations of strength and time-dependent mechanical properties, for application at temperatures exceeding 1300 °F.

The objective of this study was to assess the relaxation of stresses at increasing temperatures i... more The objective of this study was to assess the relaxation of stresses at increasing temperatures in several PM superalloy disks. The effects of temperature, time, and plasticity were examined.

Surface enhancement methods induce a layer of beneficial residual compressive stress to improve t... more Surface enhancement methods induce a layer of beneficial residual compressive stress to improve the impact (FOD) resistance and fatigue life of metallic materials. A traditional method of surface enhancement often used is shot peening, in which small steel spheres are repeatedly impinged on metallic surfaces. Shot peening is inexpensive and widely used, but the plastic deformation of 20 to 40 percent imparted by the impacts can be harmful. This plastic deformation can damage the microstructure, severely limiting the ductility and durability of the material near the surface. It has also been shown to promote accelerated relaxation of the beneficial compressive residual stresses at elevated temperatures. Lowplasticity burnishing (LPB) is being developed as an improved method for the surface enhancement of metallic materials.

The successful development of an advanced powder metallurgy disk alloy, ME3, was initiated in the... more The successful development of an advanced powder metallurgy disk alloy, ME3, was initiated in the NASA High Speed Research/Enabling Propulsion Materials (HSR/EPM) Compressor/Turbine Disk program in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. This alloy was designed using statistical screening and optimization of composition and processing variables to have extended durability at 1200°F in large disks. Disks of this alloy were produced at the conclusion of the program using a realistic scaled-up disk shape and processing to enable demonstration of these properties. The objective of the Ultra-Efficient Engine Technologies disk program was to assess the mechanical properties of these ME3 disks as functions of temperature, in order to estimate the maximum temperature capabilities of this advanced alloy. These disks were sectioned, machined into specimens, and extensively tested. Additional sub-scale disks and blanks were processed and selectively tested to explore the effects of several processing variations on mechanical properties. Results indicate the baseline ME3 alloy and process can produce 1300-1350°F temperature capabilities, dependent on detailed disk and engine design property requirements.