In the world, automobile rim production is carried out in a repeatable quality with low pressure die casting process. Traditional die coatings used to separate molds on casting mold surfaces cause significant losses in production due to their weak strength. The applicability of an alternative mold coating application with thermal sprayings has been examined in this study. MgO-ZrO 2 based ceramic thermal barrier coatings are deposited on the mold surfaces by flexicord spray method.

The application of ceramic die coatings on tool steel dies in the casting industry has been common practice for many decades. The main function of these coatings is to provide a thermal barrier to prevent premature solidification during die filling, and protect the tool steel die from the effects of molten metal during casting with aluminium alloys. Although these coatings provide good insulation they are fragile and require on-going in-situ maintenance by machine operators. These inherent poor qualities makes the die casting process difficult to control and to maintain cast product quality because the solidification pattern and porosity changes and leads to increased cast product rejects. To overcome the limitations a novel die coat has been developed for the light metal casting industry utilising thermal spraying of co-deposited MgZrO 2 and polymer particles. The coating is then thermally treated to reveal a fine network of porosity that has been found by heat transfer coefficient testing to enhance the thermal properties and overall coating durability during casting. This paper describes the porosity control system which was used to tailor the heat transfer coefficient of co-deposited MgZrO 2 and polymer coatings and compare them with the heat transfer coefficient of commercially available die coats. The inherent porosity and the overall coating thickness were found to have a large effect on the heat transfer coefficient. Results of industrial trials are also presented and show that co-deposited MgZrO 2 and polymer coatings provide considerable improvements to productivity and enhanced coating life in Gravity and Low Pressure Die casting of aluminium alloys.