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Evaluating the Role of Localised Part Properties in Corrosion Resistance of Additive Manufacturing Parts

Project Code: 34248

Start date and planned duration: February 2021, 24 months

Objectives

  • Quantify the corrosion resistance of as-built AM materials and evaluate the significance of local surface characteristics, microstructure, and porosity or micro flaws, on corrosion resistance.
  • Demonstrate process control techniques to determine the surface finish and porosity of AM parts.

Project Outline

The porosity and surface finish of additive manufactured (AM) parts have a significant influence on the corrosion behaviour of the materials, particularly in aggressive environments that may lead to pitting, crevice corrosion or stress corrosion cracking.

This project will develop optimisation procedures and quantitative experimental data on corrosion resistance of AM parts as a function of surface roughness and porosity to provide informed consultancy and recommendations to industry about the adoption of AM technologies for applications in corrosive environments. It will test and develop manufacturing procedures to control common corrosion drivers in AM of SS316L and duplex stainless steel (DSS) parts. Different AM technologies will be tested, including laser powder bed fusion (L-PBF), and laser metal deposition (LMD). AM process parameters will be developed in the two technologies to control porosity and surface roughness to determine their respective influences on corrosion performance. In order to control part properties, process parameters such as laser scan path, laser power, scan speed, hatch spacing, layer thickness, re-melting strategies, and laser focal offset will be considered.

The influence of these process parameters on surface roughness can vary with geometry and orientation, even within the same part. L-PBF parts are created with different deposition parameters for the outer surfaces and the core regions, which may result in different corrosion properties. The parameters for outer surfaces are often referred to as contour parameters. Up and down facing vertical surfaces are controlled by different upskin / downskin contour parameters respectively which may also result in differing surface roughness and microstructure at these locations

The surface roughness of a single AM part can thus exhibit different values on different faces depending on local process parameters and orientations. Such varying roughness behaviour may result in varying corrosion resistance across different faces in the same AM component. More uniform microstructures and surface characteristics can be achieved only by developing localised process parameters in the as-built part.

 

Industry Sectors

Power

Oil and Gas

 

Benefits to Industry

A successful outcome will create the following new capabilities:

  • Increased understanding of the effect of materials and processes on the corrosion resistance of AM components. This research will provide industry with information that can be used to improve corrosion resistance in the AM materials investigated, and provide guidelines for other relevant AM materials.
  • Market leading knowledge on the development of advanced L-PBF and LMD process parameters to improve corrosion resistance. The developed process parameters and manufacturing methods will be accessible to industry for future certification of AM processes and components.
  • Market leading knowledge on the effect and control of porosity, surface roughness, and anisotropy in corrosion resistance of SS316L and DSS AM materials. This will help industry to improve corrosion resistance of AM parts by implementing advanced process parameters and relevant surface finish post processing.
  • Experimental quantitative data on corrosion resistance of optimised AM components. These data will help industry to take informed decisions relevant to the adoption of AM technologies for the manufacture of corrosion-resistant components.

These are expected to generate the following benefits for industry:

  • Defined process parameters and manufacturing methods for the certification of corrosion-resistant AM parts.
  • The ability to additively manufacture corrosion resistant parts with consistent and repeatable properties.
  • Cost and time savings in the manufacture of replacement parts for corrosive environment applications. The corrosion resistance data that will be obtained will provide industry with valuable information relevant to the adoption of AM technologies for the manufacture of high urgency spare parts.
  • Quality improvement of corrosion-resistant AM parts by providing high quality materials with topology optimisation potential to optimise critical geometric-features which promote corrosion development in conventionally manufactured components.

 

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