Effects of Spray Parameters and Heat Treatment on the Microstructure and Mechanical Properties of Titanium Coatings Formed by Warm Spraying

• Published in: Journal of thermal spray technology Vol. 24; no. 8; pp. 1459 - 1479
• Main Authors: Molak, R. M., Araki, H., Watanabe, M., Katanoda, H., Ohno, N., Kuroda, S.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.12.2015
• Subjects: Analytical Chemistry; Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Machines; Manufacturing; Materials Science; Peer Reviewed; Processes; Surfaces and Interfaces; Thin Films; Tribology; microstructure; warm spraying; miniature specimen; porosity; mechanical properties
• ISSN: 1059-9630; 1544-1016
• DOI: 10.1007/s11666-015-0343-y

The microstructure and mechanical properties of Ti coatings deposited by warm spraying were investigated with the aim to find a set of optimum parameters for the spray process as well as for the subsequent heat treatment. Titanium powder was deposited with different nitrogen flow rates in a range from 0.5 to 1.5 m 3 /min. It was shown that spray parameters, which affect the temperature and velocity of in-flight particles, have significant influence on the fabricated coatings properties. Especially the increase of the warm spraying combustion pressure from 1 to 4 MPa resulted in an increase in the particle velocity to above 1100 m/s. This modification significantly increased the density and was beneficial for controlling the oxygen level in Ti coatings. Miniature tensile specimens with a total length of 9 mm were used to perform tensile tests for the Ti deposits. The optimal mechanical properties were achieved for specimens formed at a middle range of nitrogen flow rate (0.75 m 3 /min). Subsequently, several heat treatments were performed in order to enhance the mechanical properties of the as-sprayed coatings. It was found that the post-spray heat treatment significantly enhanced the strength and elongation of the Ti deposits determined by miniature specimen tensile test.