Tribological and microstructural behaviour in coatings applied using GTAW and HVOF (thermal spraying process) and used to recover AISI/SAE D2 grade tool steels

ABSTRACT

Fe-Cr-Mo alloys are used in coatings for protecting components that are subjected to conditions involving wear and corrosion. The high velocity oxygen fuel (HVOF) method used for tool steel alloys for cold working with the use of Fe-Cr-Mo substrates has yielded good results in the field of spray coatings. HOVF is a great method for applying coatings and recovering diameters that become worn down during the operating process. New surfaces and materials can be provided without the distortion caused by conventional welding processes. It is a great method for materials that are susceptible to cracking due to the formation of hard and off-balance phases with compositions with high contents of carbon and chromium, due to the conditions of the process, which combine a relatively low flame temperature and a time of low exposure. The microstructure and characteristics of the coating are determined by the physical and chemical properties of the particles impregnated in the substrate which in turn depend on a lot of parameters such as the design of the spray gun, oxygen/fuel ratio, injection method, particle size and shape, among others. This study investigates the influence of the processing parameters on the mechanical and microstructural properties of the Diamalloy 1008 coating (mixed Fe-Cr-Mo alloy), which is applied using high velocity oxygen fuel (HVOF) and five different types of electrode applied using TIG (GTAW) welding in a tool steel for cold working. These coatings are usually used as a protection against corrosion and wear, but also have the ability to recover damaged areas as is the case with stamping dies in the automotive industry. The samples were characterised using optical microscopy and scanning electron microscopy in order to evaluate the quality of the material deposited on the substrate; Vickers microhardness and Pin-Ball Disc were used to quantify the mechanical properties of the coatings.

KEYWORDS:

• GTAW
• HVOF
• wear

Acknowledgments

The Editorial Board would like to thank all authors and readers of this journal.

Additional information

Funding

This work was supported by the Brazilian Welding Association.