Influence of cold-sprayed, warm-sprayed, and plasma-sprayed layers deposition on fatigue properties of steel specimens

• Main Authors: Cizek, J., Matejkova, M., Dlouhy, I., Siska, F., Kay, C. M., Karthikeyan, J., Kuroda, S., Kovarik, O., Siegl, J., Loke, K., Khor, Khiam Aik
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Article
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Materials::Material testing and characterization
• Online Access: https://hdl.handle.net/10356/107368; http://hdl.handle.net/10220/25626
• Institution: Nanyang Technological University

Titanium powder was deposited onto steel specimens using four thermal spray technologies: plasma spray, low-pressure cold spray, portable cold spray, and warm spray. The specimens were then subjected to strain-controlled cyclic bending test in a dedicated in-house built device. The crack propagation was monitored by observing the changes in the resonance frequency of the samples. For each series, the number of cycles corresponding to a pre-defined specimen cross-section damage was used as a performance indicator. It was found that the grit-blasting procedure did not alter the fatigue properties of the steel specimens (1% increase as compared to as-received set), while the deposition of coatings via all four thermal spray technologies significantly increased the measured fatigue lives. The three high-velocity technologies led to an increase of relative lives to 234% (low-pressure cold spray), 210% (portable cold spray), and 355% (warm spray) and the deposition using plasma spray led to an increase of relative lives to 303%. The observed increase of high-velocity technologies (cold and warm spray) could be attributed to a combination of homogeneous fatigue-resistant coatings and induction of peening stresses into the substrates via the impingement of the high-kinetic energy particles. Given the intrinsic character of the plasma jet (low-velocity impact of semi/molten particles) and the mostly ceramic character of the coating (oxides, nitrides), a hypothesis based on non-linear coatings behavior is provided in the paper.