片狀石墨／球狀石墨鑄鐵熱浸鋁塗層之恆溫與熱循環氧化

Isothermal and Thermal Cycling Oxidation of Hot-dip Aluminide Coatings on Flake/Spheroidal Graphite Cast Irons

本研究使用熱浸鍍鋁施加鋁塗層在兩種成份相似且為肥粒鐵基地之鑄鐵材料——片狀石墨鑄鐵與球狀石墨鑄鐵，探討石墨形態對鑄鐵鋁塗層高溫氧化行為的影響。鑄鐵表面之熱浸鋁塗層是由純鋁層、鐵鋁介金屬層與石墨所組成。恆溫氧化與熱循環動力學結果顯示，塗覆鋁塗層之鑄鐵材料其氧化速率低於未塗覆塗層之鑄鐵材料。然而，由於兩類鑄鐵材料的石墨型態差異，使得兩類鑄鐵材料之熱浸鋁塗層的抗高溫氧化與熱疲勞能力也具有明顯的差異。片狀石墨鑄鐵之鋁塗層的抗高溫氧化性與抗熱疲勞性皆低於球狀墨鑄鐵之鋁塗層的抗高溫氧化性與抗熱疲勞性。

Two types of cast irons, flake graphite and spheroidal graphite, with a common ferrite matrix and similar compositions, were aluminized by hot-dipping. The as-coated aluminide layer consisted of an outer Al topcoat, an inner Fe-Al intermetallic layer, and dispersed graphite. Isothermal and thermal cycling oxidation tests on aluminized specimens were conducted. Cast irons with aluminide coatings exhibited a higher oxidation resistance than those without coatings. However, variations in graphite structure resulted in differences in the quality of the aluminide coatings. The aluminide coating on the flake graphite cast iron exhibited a less oxidation resistance and adhesion to the substrate.