Study of CVD overaluminising on different CoNiCrAlY bond coats deposited by HighVelocity Oxygen Fuel (HVOF), Low Pressure Plasma Spray (LPPS) and Vacuum PlasmaSpray (VPS)

摘要

Coating technology is progressing at a steady rate with continuous significant improvements in the coatingsperformance. In the aerospace field, as well as in the stationary gas turbine field, coatings deposited by differentprocesses (thermal spray, CVD, EBPVD) play an important role in order to increase the performances of theengines. In particular, in order to improve the resistance to oxidation and corrosion at high temperature, aluminiumis deposited by several techniques (pack aluminising, above the pack and CVD) in alternative or addition to thermalspray coatings (mainly MCrAlY alloys where M stands for Co, Ni or CoNi). These MCrAlY coatings are generallydeposited by Low Pressure Plasma Spray (LPPS) or Vacuum Plasma Spray (VPS), but also by High VelocityOxygen Fuel (HVOF) and Air Plasma Spray (APS). This paper addresses the study of aluminium coatingsdeposited by CVD on CoNiCrAlY bond coats deposited by different processes: VPS with F4 gun, LPPS with EPIgun and HVOF. The aim is to verify if and how the different CoNiCrAlY coatings obtained by these three processeswith different content of oxides and porosity could affect the deposition rate and quality of the Al coatings. Theobtained samples have been characterized from the metallographic point of view in order to determine porosity,thickness and structure of both CoNiCrAlY and Al coatings. Al coating thickness has been taken as parameter inorder to define the Al coating deposition rate on the three different CoNiCrAlY coatings. Further tests for thedetermination of aluminium content and chemical composition of the coatings are in progress.