The deposition of yttria partially stabilised zirconia (PYSZ) onto aluminum alloy substrates using PVD techniques

Abstract

Yttria partially stabilised zirconia (PYSZ) has been shown to be a very effective material for use as a thermal barrier coating (TBC) in the aerospace industry. In the future however, TBCs will be used increasingly in internal combustion engines, in particular for adiabatic diesel engines and also in increasing the operating temperature of exhaust gases to enable the more efficient operation of catalytic converters. Internal combustion engines are likely to be increasingly manufactured from aluminium alloys, and this paper is therefore a report of a preliminary investigation looking at the feasibility of depositing PYSZ onto such materials using the r.f. PAPVD technique, employing electron beam evaporation and a 13.56 MHz r.f. power supply. Of particular interest in this work is the effect of the sputter etching times on the substrate, in terms of the adhesion and properties of the coating. The coatings have been tested with respect to their phase composition, microhardness, adhesion, thickness and surface morphology using a range of techniques including X-ray diffraction, EDX, SEM, ball cratering, microhardness testing, surface profilometry and scratch testing. The main results from these tests are reported.