Advances in Surface Engineering II: Session I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Surface Engineering Committee
Program Organizers: Tushar Borkar, Cleveland State University; Arif Mubarok, PPG; Rajeev Gupta, North Carolina State University; Sandip Harimkar, Oklahoma State University; Tanaji Paul, Florida International University
Monday 8:00 AM
February 24, 2020
Room: 9
Location: San Diego Convention Ctr
Session Chair: Rajeev Gupta, North Carolina State University
8:00 AM
Characterization of Precipitates Evolution in Laser Assisted Cold Spray of AA7050 and AA7075: Ning Zhu1; Luke Brewer1; 1University of Alabama Tuscaloosa
This presentation describes the evolution of precipitates during laser assisted cold spray (LACS) of AA7050 and AA7075. LACS improves the deposition efficiency compared to conventional cold spray by thermal softening of the substrate using in situ laser heating. The mechanical properties of AA7xxx alloys strongly depend on the size distribution of metastable precipitates. As such, the thermal profiles during deposition are key to strengthening the material without overaging it. AA7050 and AA7075 materials were deposited using cold spray both with and without laser heating. Electron microscopy is being applied to characterize the size distribution of precipitates in the starting powders, cold spray deposits and LACS deposits as a function of heat input from the laser. As the laser heat input increases, we have observed coarsening of both η phase precipitates and the aluminum grain size. Laser heat treatment also impacts the precipitate distribution in the substrate for larger heat inputs.
8:20 AM
Enhanced Bond Durability of 7xxx Automotive Alloy by Surface Modification: Theresa Macfarlane1; Tudor Piroteala1; Rashmi Monty1; Sazol Das1; Yudie Yuan1; Thomas Beck1; Lasitha Cumaranatunge1; 1Novelis Inc
Aluminum alloys have been used in the aerospace industry since the late 19th century because of their strength and light weighting ability. Among those alloys, 7xxx alloys are commonly used due to their high strength-to-weight ratio. With increased pressures to improve fuel economy of vehicles, 7xxx alloys are now being looked at for automotive applications where structural bonding is required. This study will review bond durability data generated with 7xxx alloys, prepared using conventional processing as well as using new surface modification techniques, where significant improvements in these bond durability test results have been seen. Data comparing these modified surfaces using techniques such as XPS, TEM, SEM and electrochemical measurements will also be discussed. In conclusion, this review will show that whilst these highly alloyed aluminum alloys may need to be treated differently to ensure good bond durability performance, they are certainly capable of meeting the performance requirement.
8:40 AM
Surface Chemistry and Subsurface Microstructure after Spot-by-spot laser-interference Processing of Al 2024-T3: Adrian Sabau1; Harry Meyer1; Donovan Leonard1; 1Oak Ridge National Laboratory
For adhesive joining and coating applications, non-chemical surface preparation techniques are needed to reduce the environmental impact and associated costs with chemical surface preparation. In this study, a laser-interference technique was employed for surface preparation of Al 2024-T3. The laser-interference power profile was created by splitting the beam and guiding both beams on the same spot, creating a line-interference pattern on the specimen surface. The specimens were laser-structured in the as-received condition with no additional surface preparation steps. The x-ray photoelectron spectroscopy was used to assess the “cleaning” of the surface and the extent of oxide layer regrowth. the scanning electron microscopy STEM was used to characterize the sub-surface microstructure modifications, such as the depth of heat-affected zone and precipitate dissolution. The scanning electron microscopy was used to assess changes in morphology of the Al surface, such as smoothing out of the sharp features in the as received Al sheet.
9:00 AM Invited
Multilayer, Multifunctional Thermal Coatings Enabled by Layered Manufacturing: Sanjay Sampath1; 1Stony Brook University
Overlay coatings find extensive applications in industry serving to protect components from wear, heat, electrical damage and corrosion. Coatings are first lines of defense for structures and components subjected to extreme environments. Specifically thermal sprayed coatings are used in aerospace, energy, heavy machinery, automotive and electronics. Coatings are various types including ceramics, materials, cermets and composites based on combinations there-of. Much of the current thermal sprayed overlays and usually monolithic single layers. However, there are many applications where the coating attributes needs to be multifunctional, especially where a variety of environmental degradation mechanisms occur concurrently. One approach to seek multifunctionality is through 2D/3D layered design and manufacturing. Thermal spray naturally lends itself to such opportunities as coatings are built in layers allowing optimization of chemistry, stress and microstructure through thickness. This presentation will overview examples of these strategies for applications and identify the fundamental issues.
9:40 AM Break
10:00 AM
Laser Assisted Cold Spray Applied to Austenitic Stainless Steel: Venkata Satish Bhattiprolu1; Luke Brewer1; 1University of Alabama
This presentation will show the microstructural and mechanical response of 304 stainless steel material produced by the laser assisted cold spray (LACS) process. LACS involves in situ laser heating of supersonically sprayed metallic powder in the particle size range 40-50 µm in diameter. In the recent past, cold spray has been implemented with good success for additive repair of various metallic components. Cold sprayed stainless steel often possesses limited ductility due to extensive strain hardening during the particle impact process. To enhance ductility, we have deposited 304 stainless steel using high pressure nitrogen gas spray, while applying in situ laser heating. Detailed analysis employing electron microscopy, diffraction, and micro/nanohardness are being used to capture the mechanical response and evolution of the microstructure. We will present initial results showing the ability of the laser heating to recrystallize the cold sprayed particle microstructure, in turn improving the ductility of the coating.
10:20 AM
High Temperature Oxidation Behaviors of SiON Coated AISI 441 in Different Atmospheres: Kathy Lu1; Kaustubh Bawane1; Rajendra Bordia2; 1Virginia Polytechnic Institute and State University; 2Clemson University
Silicon oxynitride (SiON) coated AISI 441 was prepared using pyrolysis of dip coated perhydropolysilazane (PHPS) precursor polymer. The high-temperature oxidation behaviors of SiON coated AISI 441 substrates were studied in Ar+O2, Ar+H2O, and Ar+CO2 atmospheres at 800°C for 100 hours. The SiON coated AISI substrates showed better performance in all three atmospheres as compared to the uncoated AISI 441 substrate. The result was attributed to the dense, crack free SiON coating which provided complete separation between oxidizing species and the steel substrate. The thin oxide scale was observed on top of the SiON coating for all the atmospheres, which was attributed to the diffusion of metallic species (Cr, Mn, and Fe) in the AISI 441 substrate through the SiON coating.
10:40 AM
Contact Angle Measurement Comparisons of Common Additive Materials and Processes: Holly Martin1; Arthur Kasson2; Ibrahim Al Qanber1; Brett Conner1; 1Youngstown State University; 2KRUSS USA
The wettability and surface energy of materials is important to understand because it demonstrates the tendency of a liquid material to spread across solid surfaces. The more easily a liquid spreads across the solid, the higher the wettability and surface energy of that surface. This spreading of liquids is vitally important in the use of binder jet printing, where the metal powder is held together by a binder material. To ensure that the metal powder and binder material adhere together, the metal powder must be adequately wetted by the binder. The KRUSS Drop Shape Analyzer 100 allows for the examination of contact angles and surface energy for both solid surfaces and powder materials. Various particle size distributions powders and sands will be examined with water and with the binder material to determine wettability, while the surface energy will be determined using water and diiodomethane.
11:00 AM
Investigation on the Laser Surface Treatment of Steel and Aluminum with a Single Mode Pulsed Fiber Laser Source: Quentin Perry Auger1; Jean-Michaël Deschênes1; Alex Fraser1; 1Laserax Inc
The effects of modifying the microstructure of a surface on its macroscopic properties have been studied intensively in the last decade, a well-known example being the generation of superhydrophobic surfaces with laser beams. For such kind of surface treatment, where the surface roughness (Ra value) is typically either increased or decreased, pulsed fiber lasers are an excellent tool. By focusing energy into a small spot on the surface, local intensity greater than the ablation threshold of the material can be reached and a portion of it is removed from the surface. Controlling the size and spacing of each of these holes or trenches allows to precisely modify the roughness. For this study, we used a single mode pulsed fiber laser combined with a high-speed galvanometer scanner. Several parameters of the process were optimized in order to determine the induced roughness rate achievable at full power on steel and aluminum.