Microstructural and tribological studies of as-sprayed and heat-treated HVOF Cr3C2–CoNiCrAlY coatings with a CoNiCrAlY bond coat

• The heat treatment of the coating produced a hardness decrease inside the coating.
• The coating heat treatment caused a hardness increase on the top coating surface.
• The oxidation of the top coating surface produces a reduction of the wear rate.
• The use of a bond coat improves the thermal shock resistance of the system.
• HVOF coating is proposed to prolong the life of dies in hot-working processes.

Die wear is an important problem for manufacturers in hot-working processes, e.g. metal die casting, hot extrusion and thixoextrusion of aluminium, magnesium or steel, as well as glass and plastics processing. The dies have to be capable of withstanding complex thermal and mechanical loads, while giving a sufficient wear resistance against abrasion and adhesion at very high temperatures. In order to improve the wear resistance and reduce the heating of the extrusion die it can be protected with a hard cermet coating. The purpose of this work is to study the high-temperature performance of Cr3C2–CoNiCrAlY coating and explore the potential application of this coating to prolong the life of tooling and dies while reducing maintenance and increasing shelf life and dimensional control. A 75Cr3C2–25CoNiCrAlY coating with a CoNiCrAlY bond coat was sprayed by HVOF thermal spray process on a steel substrate. Coatings were heat-treated at a range of temperatures between 900 °C and 1100 °C. The mechanical and tribological properties of coatings were determined as a function of the temperature of heat treatment. The bond coat effect on the thermal shock resistance of Cr3C2–CoNiCrAlY coating was analysed.