Presentation Title

Pack Aluminizing of Iron, Nickel and Cobalt – A Comparative Study

Faculty Mentor

Dr. Vilupanur Ravi, Chemical and Materials Engineering, Cal Poly Pomona

Start Date

17-11-2018 1:30 PM

End Date

17-11-2018 1:45 PM

Location

C302

Session

Oral 3

Type of Presentation

Oral Talk

Subject Area

engineering_computer_science

Abstract

Surface modification is a cost-effective way to improve the lifetimes of industrial metal alloys in high temperature corrosive environments. The pack cementation method is an efficient way to achieve protective coatings. A fundamental understanding of this process as applied to pure metals can provide the deep insights needed to coat more complex, multicomponent alloys. In this study, the effect of pack process variables, i.e., temperature, time and pack compositions, on coating characteristics (thickness, mass change, microstructures) for pure metals - iron, nickel and cobalt, was examined. Each of these metals has a different crystal structure. They are also the main constituent of a large number of engineering alloys. Optical and scanning electron microscopy were utilized to characterize the aluminide coatings produced using HAPC method to obtain quantitative thickness measurements as well as selected microstructural features. The type of substrate material had a dramatic effect on the formation of aluminide coatings on their surface. A comparative analysis of the same will be presented.

Summary of research results to be presented

The substrate that is being coated has a significant effect on the morphology of the coating produced and affects the possibility of producing a successful coating with good adherence and consistent coverage. Across all coating parameters used in this experiment, the coatings on Ni substrates have the thickest (up to ~70 μm) and the most consistent coating thickness (lowest coefficient of variation, 10%), while those on Fe have the least consistent coating thickness (~ 50% CV). Comparing AlCl3 and NH4Cl activators, the latter produced more uniform coatings on Fe and Co while the coatings thicknesses were the most consistent for Ni substrates in each of these packs. It was seen that aluminide coatings on cobalt substrates at either temperature (650°C or 750°C) and with either activator had similar microstructures, composed of an inner layer with a fairly uniform morphology, a middle layer with narrow columnar grains, and an outer layer with long and narrow columnar grains. Likewise, coatings produced on nickel substrates at either temperature and with either activator had similar microstructures and were thicker than coatings on iron and cobalt for each corresponding set of coating conditions. The coatings on nickel consisted of a thin inner layer and an outer layer of equiaxed grains. The grains of the outer layer varied in size, with a higher concentration of very fine grains seen near the inner layer. Successful coatings on Fe were not produced at 650°C due to the inconsistent coverage and poor adherence.

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Nov 17th, 1:30 PM Nov 17th, 1:45 PM

Pack Aluminizing of Iron, Nickel and Cobalt – A Comparative Study

C302

Surface modification is a cost-effective way to improve the lifetimes of industrial metal alloys in high temperature corrosive environments. The pack cementation method is an efficient way to achieve protective coatings. A fundamental understanding of this process as applied to pure metals can provide the deep insights needed to coat more complex, multicomponent alloys. In this study, the effect of pack process variables, i.e., temperature, time and pack compositions, on coating characteristics (thickness, mass change, microstructures) for pure metals - iron, nickel and cobalt, was examined. Each of these metals has a different crystal structure. They are also the main constituent of a large number of engineering alloys. Optical and scanning electron microscopy were utilized to characterize the aluminide coatings produced using HAPC method to obtain quantitative thickness measurements as well as selected microstructural features. The type of substrate material had a dramatic effect on the formation of aluminide coatings on their surface. A comparative analysis of the same will be presented.