Metallurgy Commons^™

Effect Of Oxidation On Weld Strengthof Dissimilar Resistance Weld Interface Between 304 Stainless Steeland Near Equiatomic Austenitic Nitinol Guide Wire, Matthew Rudow

Master's Theses

Abbott Vascular encountered strength and variability issues when attempting to resistively weld 304 Stainless Steel to equiatomic Nitinol. Initial observations suggested that passivation layer (Cr₂O₃, TiO₂) formation affected the weld interface. One hundred 304 Stainless Steel/Nitinol pairs were allowed to oxidize in air at room temperature for allowed periods of time (.1, 1, 3, 5, 7, 12, 16, 24, 168, and 336 hours). Each pair was welded resistively with constant current. A Miyachi/Unitek Advanced Data Analysis Monitor (ADAM) recorded the peak resistance at the instance the weld was made. Resistances were compared to Instron …

Characterization And Analysis Of Low Room Temperature Ductility Nickel-Based Superalloy 718 Plus For Aircraft Engine Forgings, Jonathon Bracci

Materials Engineering

Schlosser Forge Co. forges low pressure turbine (LPT) cases from the nickel based superalloy 718 Plus using the ring rolling forging process. Schlosser has been experiencing low room temperature ductility problems in a number of their 718 Plus LPT cases. LPT cases are required to pass a 4D tensile test at room temperature with a minimum of 15 percent elongation. The ductility problem was reduced by increasing the forging temperature from 1825˚F to 1850˚F. Analysis was performed on 718 Plus samples taken from forged LPT cases that failed the room temperature ductility requirement and ones that passed the requirement. The …

Effects Of Beta Stabilizers On Quench Delay Susceptibility Of Ti-6al-4v, Kyle Logan

Materials Engineering

Tensile samples of Titanium 6Al-4V (Ti-6Al-4V) were machined from forgings containing rich and poor amounts of beta stabilizers in their compositions. The tensile samples were each heat treated two times. In the first round of heat treatments, the samples were either beta solution treated (BST), or solution treated (ST). Each sample was water quenched with varying quench delays of 10, 20, and 30 seconds. BST treated specimens were then overaged at 1350°F for 2 hours and air cooled (BSTOA); while the ST treated samples were aged at 990°F for 6 hours and air cooled (STA). Following heat treating, the tensile …

Microstructural Characterization Of Ti-6al-4v And Its Relationship To Sample Geometry, Blake Gaspar

Materials Engineering

A problem exists with a part produced by forging made by Shultz Steel of Ti-6Al-4V in the variance of properties throughout the part. There is one specific region that exhibits the most variance. The purpose of the report is to determine any microstructural differences within the region of interest in the part. When microstructures of the inner section and outer section of the part were looked at it was determined that they exhibited a martensitic structure. There was a noticeable difference in the lath structure between sections. The outer region contained larger more widely spread laths of an average length …

Morphology And Roughness Of Al2o3 On Ferritic Stainless Steel Foil For Diesel Catalytic Converter Applications, Megan Butala

Materials Engineering

The improved thermal properties of metal-substrate catalytic converters enable effective catalysis sooner after ignition than traditional ceramic monoliths, resulting in less harmful emissions. ACAT Global, a manufacturer of stainless steel catalytic converters, uses ferritic stainless steel substrates for low temperature catalytic converters for diesel automobiles. Production begins with an oxidizing heat treatment to increase surface roughness. The success of the second production step, the application of catalyst-containing ceramic slurry (washcoat), depends on the surface roughness that results from oxidation. Formation of the primary oxide of interest, alumina (Al₂O₃), is controlled by the stainless steel foil composition, …

Discontinuous Grain Boundaries Of Forged René 41, Steven Crump

Materials Engineering

Forged components must pass a grain size specification (grain size, distribution) for acceptance in an application. The varying amounts of plastic deformation during forging can lead to abnormally large recrystallized grain sizes in certain regions of the part, which will not pass specification. The question exists whether these abnormally coarse grains are truly comprised of poly crystalline fine grains with grain boundaries resistant to etching techniques. To investigate this abnormal grain size effect, a cross section of a forged René 41 nickel-based superalloy aircraft engine ring was cut and sectioned into six segments. Those segments were then prepared for microstructural …

Analyzing The Corrosion Resistance Of Ni-Shield 200 Coatings At Different Temperatures When Exposed To Sulphuric Acid, Alex Hussinger

Materials Engineering

Six steel samples each were twin wire arc sprayed with Hastelloy C-276 or Nickel-Shield 200 coatings approximately 0.020″ thick. These samples were then cut into 3″ by 3″ squares. A 2″ diamond grit hole saw was used to abrade and polish to a smooth surface a ring in the middle in order to get an O-ring mechanical seal. The samples were then weighed and loaded into a jig that started from the bottom up with a stainless steel plate, then the sample, then a Viton O-ring, a ¾″ thick glass plate with a 1 3/4″ hole cut in it, another …

Characterization Of Positive Macrosegregation At The Subsurface Of Direct-Chill Cast 7050 Aluminum Forging Billets, Aaron Youril

Materials Engineering

Segregation of alloying elements during casting of forging billets may persist to the final forged component leading to unacceptable surface appearance. Determination of the elements or compounds that segregate is the essential first step to solving this problem. Differential Scanning Calorimetry (DSC) was used to determine a composition profile of the macrosegregation occurring at the subsurface of an as-cast 7050 aluminum alloy billet. Data collection was carried out by separating 10 to 20 mg samples from the outer centimeter along the radius of the billet, as well as samples from the bulk interior of the billet for comparison with the …

Effect Of Heating Temperature, Heating Time And Initial Microstructure On Recrystallization Of Waspaloy During Heating For Forging, Marissa Hill

Materials Engineering

A fine, uniform grain size is required for creep limited Waspaloy in aircraft engine applications. Upon heating, Waspaloy does not always recrystallize in a uniform manner resulting in occasional large grains with a majority of the grains meeting the grain size requirements. Waspaloy’s microstructure was analyzed with different heat treatments and in the as-forged condition. The strengthening mechanism is the gamma prime phase. The gamma prime solvus temperature is 1908°F so the different heat treatments were determined around that temperature, as well as the forging temperature range of 1800-2150°F. At the 1850°F heat treatment, the microstructure recrystallized with small grains, …

A Quantitative Study Of The Weldability Of Inconel 718 Using Gleeble And Varestraint Test Methods, Sean Quigley

Master's Theses

Nickel super alloy Inconel 718 was tested and compared to Haynes 230 using Gleeble and Varestraint mechanical test methods. Hot cracking susceptibility was examined in either alloy using a sub-scale Varestraint test method at 5 augmented strain levels: 0.25%, 05.%, 1%, 2%, and 4%. Maximum crack length, total crack length, and number of cracks were measured for each strain level. Gleeble hot ductility on-heating and on-cooling tests were performed on both alloys. Inconel 718 was tested on-heating at target temperatures of 1600˚F, 2000˚F, 2100˚F, 2200˚F, and on cooling at 1600˚F, 1700˚F, 1800˚F, 1900˚F, and 2100˚F. Haynes 230 was tested on-heating …

Design, Fabrication, And Characterization Of A Thin-Film Nickel-Titanium Shape Memory Alloy Diaphragm For Use In Micro-Electro-Mechanical Systems, Brian Joel Alvarez

Master's Theses

Previous work done at Cal Poly has shown that thin-film nickel-titanium (NiTi) can be easily sputtered onto silicon wafers and annealed to create a crystallized shape memory alloy (SMA) film. Initial work on creating devices yielded cantilevers that were highly warped due to thin-film stress created during the sputtering process. The objective of this work was to create a thin-film NiTi SMA device that could be better characterized. A membrane was selected due to the simplicity of fabrication and testing which would also oppose the thin-film stress due to the increase in attachment points to the substrate.

Silicon wafers were …

Effect Of Au Content On Microstructural Evolution Of Snagcu Solder Joints That Undergo Isothermal Aging And Reliability Testing, Patrick J. Hyland

Master's Theses

Electronics, especially, printed circuit boards (PCBs) are a widespread technology. Metal coatings or “surface finishes” are often added to PCB board pads and component leads during manufacturing to improve their performance. Electroplated nickel/gold over copper is a popular surface finish for printed circuit boards and component leads. The presence of gold in solder joints, however, is known to have detrimental effects referred to as gold embrittlement. It is generally understood that tin-lead solder joints with less than 3 weight percent (wt%) of gold will not experience reliability issues. The acceptable level of gold in lead-free solder joints, however, is less …

Dissimilar Metal Weld Variability Due To Lot Differences In Nitinol/ Stainless Steel Interface, Matthew R. Rudow

Materials Engineering

Abstract

An experiment was conducted to determine and reduce the causes of variation between a 304 Stainless Steel and super elastic Nickel Titanium dissimilar metal weld. Six factors were established to understand the cause of variation: perpendicularity, final grind, surface finish, weld force, weld pulse duration, and alignment. Using a rotational test with an air piston break pressures were established and charted in Minitab to identify trends. It was shown that weld force and weld pulse duration were the two factors that had the most influence on break strength. This data also showed that higher strength groups had less variability. …

The Effects Of Heat Treatment On Area Percent Porosity And Corrosion Behavior Of High-Nickel Thermal Spray Coatings, Travis Crowe, Alec Guraydin

Materials Engineering

Samples of two Thermal Spray Coating (TSC) alloys on a low carbon steel substrate were obtained: alloy C276 and Nicko-Shield 200. Specimens of each alloy were subjected to heat treatments at temperatures at 1100° for 60 minutes and 1200° for 10 minutes, with some specimens left in the as-sprayed condition. Three replicates were prepared for each condition. Thin 1” strips were cut using a diamond wafering blade for porosity measurements and 2” x 1” specimens were cut for corrosion testing using a SiC abrasive saw. The porosity specimens were mounted in acrylic resin, polished, and examined using SEM. From these …

Characterization Of The Relationship Between The Microstructure And Tensile Strength Of Annealed Ti-6al-4v, Aldo Corona

Materials Engineering

Tensile coupons of Ti-6Al-4V were heat treated at varying annealing temperatures from 1200°F (648°C) to 1450°F (787°C)  at 50°F  (23°C) increments for 1 hour. The samples were air cooled to room temperature or furnace cooled to 800°F (426°C) followed by air cooling to room temperature. Four tensile coupons were treated at each annealing temperature and cooling rate. Alpha case was observed to form on the surface of the samples post heat treatment with a maximum depth of 25 µm (.001 in). Samples were tensile tested for their ultimate tensile strength, yield strength, and percent elongation.  Samples across all annealing temperatures …

Characterization Of Inconel 718: Using The Gleeble And Varestraint Testing Methods To Determine The Weldability Of Inconel 718, Nathaniel Oscar Knock

Master's Theses

Nickel based superalloys were developed to withstand the severe thermal and mechanical environment associated with rocket propulsion systems and jet engines. In many alloy systems the strength of a component rapidly deteriorates as the operating temperature increases. Nickel based superalloys, however, retain strength over a range of temperatures which includes the operating range for many propulsion systems. This improved performance is accomplished by a combination of solid-solution strengthening, precipitation strengthening and grain-boundary strengthening. Furthermore, super-alloy systems are designed for ease of fabrication, to include machining, welding and heat treating. Inconel 718 was developed to overcome problems with post-weld cracking that …

The Effects Of Applied Strain And Heat Treatment On The Properties Of Niti Wire During Shape Setting, Frank Zapoticla

Master's Theses

NiTi components are commonly subjected to thermo-mechanical heat treatments during production and fabrication. This study investigates the effects of applied strain of 0-10% and heat treatments of 300-600ºC for times of 2-30 minutes during shape-setting of Ti–50.8 at% Ni wire with a nominal diameter of 0.495 mm and an initial transition temperature, Af, of 12ºC. Strain was applied prior to heat treatments by coiling NiTi wire, essentially producing coiled springs, around different diameter steel mandrels to obtain different strain levels. The samples of NiTi wire under applied strain were heat treated in a salt bath, followed by a rapid quench. …

The Effects Of Carbon, Boron And Vanadium On The Microstructural Evolution And Hardness Of Steel-Based Hardfacing Alloys, Kyle Rafa

Materials Engineering

Current hardfacing alloys provide insufficient wear resistance due to either cracking or significant material wear. To increase wear resistance of steel-based hardfacing alloys, the effects of composition on microstructure and hardness were investigated in a progression of alloys. Initially, seven new alloys were prepared varying the carbon-boron ratio with the total constant at 3 wt%. Small arc-melt cast circular ingots were produced roughly 1 x 0.5 inches. Metallography provided insufficient phase magnification, thus a SEM equipped with EDS was used, allowing for microstructure and phase composition analysis. Four distinct carbide phases were found and image analysis software allowed for carbide …

Characterization Of Aluminum-Boron Carbide Particulate Metal Matrix Composites, Eric Blank

Materials Engineering

The analysis of die-cast 380 aluminum-boron carbide particulate metal matrix composites (MMC) was performed in order to see if the samples had the required tensile strength of 300 MPa. 10wt% B4C die-cast samples were produced and tested. Half were heat treated to the T6 condition and the others were left as cast. Using ASTM standard B 557M it was found that the average tensile strength for the as-cast samples was 130 MPa and the heat treated samples had a tensile strength of 93 MPa. These values were both lower than expected. The heat treated samples were not expected to have …

Effects Of A Solution Anneal Quench Delay On The Heat Treatment Response Of Aluminum 2219-T6, Daniel James Filomeo

Materials Engineering

The ageing response for aluminum 2219-T6 was investigated to determine the effects a quench delay (QD) could have on tensile properties. Before testing commenced, furnace surveys were conducted to ensure they could meet the required temperature stability of + 10˚F (+6˚C). MIL-H-6088 specified a maximum quench delay of 15 seconds for parts thicker than 2.29 mm (0.090 in). An investigation was conducted on how different quench delay times changed the ageing response of T6 heat treated for Al 2219. Heat treatments were performed according to the ASM Handbook. Preliminary tests were performed on 1-1.5 in. cube blocks of Al 2219 …

Shielding Effectiveness Of Superalloy, Aluminum, And Mumetal Shielding Tapes, Cindy Suit Cheung

Master's Theses

Using MIL-HDBK-419A, MATLAB and Nomographs, Shielding Effectiveness for the Magnetic Field, Electric Field, and Plane Wave were calculated over a frequency range from 10 Hz to 1 GHz. The three shielding tapes used included superalloy, aluminum, and mumetal. Calculations for Shielding Effectiveness involve the computation of Absorption Loss, Reflection Loss, and Re-Reflection Correction Factor. From the outcome of the calculations, it was suitable to conclude that all three metals fulfill the 40 dB Shielding Effectiveness requirements for SGEMP fields for frequencies greater or equal to 1 MHz. Accordingly, all three shielding tapes provide at least 40 dB of shielding to …