Korean Institute of Surface Engineering

pISSN : 1225-8024 | eISSN : 3399-8403


공학

한국표면공학회지 (29권3호 163-175)

Microstructure and Thermal Fatigue Properties of Flame-Sprayed Nickel-Based Coatings

니켈계 용사층의 조직 및 열피로 특성

김형준;권영각;

포항산업과학연구원, 설비기술연구팀;

Abstract

Flame-sprayed Ni-based coatings are investigated in order to improve the thermal fatigue properties of gray cast iron in the presence of water spraying. The results of thermal cycling tests from room temperature to $1100^{circ}C$ indicate that thermal fatigue endurance is increased in the order of Ni-20%Cr, NiCr-6%Al, and Ni-5%Al. The thermal fatigue failure is caused by the formation of iron oxides between the coating and the substrate and then the thermal fatigue cracks have propagated either along the brittle iron oxide layer resulting in the spatting of the coatings in case of Ni-5%Al and NiCr-6%Al coatings or to the substrate resulting in the whole specimen fracture in case of Ni-20%Cr coating. It seems that the most governing factor for thermal fatigue resistance is the thermal expansion coefficient difference between the coating and the substrate. Microstructural variations before and after the tests are also discussed.

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