Heat insulation coat, coated member, and method of manufacturing coated member

Abstract

[Technical Problem] An object is to provide a heat insulation coat having a novel form/structure different from conventional ones. [Solution to Problem] The present invention provides a heat insulation coat having a spongy body that is composed of non-linear pores and a skeleton incorporating the pores. The skeleton is an amorphous body comprising Al, Si, O, and impurities and has an amorphous peak specified by X-ray diffraction analysis at a position of 3.5 Å or more as the lattice spacing. The heat insulation coat has an apparent density of 1 g/cmor less, a volumetric specific heat of 1,000 kJ/m·K or less, and a thermal conductivity of 2 W/m·K or less. The spongy body is obtained through forming a base layer, such as by thermal-spraying an aluminum alloy that contains a large amount of Si, and performing an anodizing process by AC/DC superimposition energization on the base layer. The amount of Si in the base layer may be, for example, 16 to 48 mass % with respect to the alloy as a whole. The heat insulation coat of the present invention is excellent in the swing characteristics and may be provided on the inner wall surface of a combustion chamber of an internal combustion engine.