Development of protective MMC coating on TZM alloy for high temperature oxidation resistance by LPCS


Kılıçay K.

SURFACE & COATINGS TECHNOLOGY, vol.393, 2020 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 393
  • Publication Date: 2020
  • Doi Number: 10.1016/j.surfcoat.2020.125777
  • Title of Journal : SURFACE & COATINGS TECHNOLOGY

Abstract

TZM is an important Mo based alloy for high temperature applications, however, oxide structures formed in an air atmosphere at high temperatures restrict its commercial applications. In this study, TZM alloys were coated with Ni-Zn-Al2O3 by low pressure cold spray (LPCS) in order to improve the high temperature oxidation behaviour. The effects on the microstructure, oxidation, and tribological properties of the MMC protective coating were examined. According to microstructural examinations, the LPCS solid-state coating had a wave-like lamellar structure due to an interlocking mechanism and consisted of ceramic alumina particles embedded in a Ni and Zn metal matrix. The EDS and XRD results showed that phase changes or oxidation were not formed in the LPCS coating due to the solid state deposition mechanism and low process temperature. The oxidation test results showed that the specific mass losses of the TZM alloy were sharply increased at high temperature due to the deformation of the oxygen in the molybdenum matrix. The Ni-Zn-Al2O3 MMC coating prevented oxidation on the TZM alloy at 600-1000 degrees C due to the reaction of the oxygen with the Ni and Zn elements generating a NiO and ZnO protective film layer on the coating surface. Dry sliding tests of the MMC coating were performed at different test loads for determination of the tribological performance. Although MMC coatings showed similar friction behaviour at different test loads, the wear rate in the 4 N test load was about 1.2 times higher than the 2 N loading.