The present invention relates to a thermal spray coating made of cermet, and a thermal spray powder used to gain such a thermal spray coating.
It is known according to the prior art to provide a thermal spray coating made of cermet on the surface of the cavity of a die casting mold and on the surface of a roll in a hot dip plating bath in order to prevent damage caused by melted metal. Japanese Laid-Open Patent Publication No. 2004-300555 discloses a thermal spray material which is useful for such an application.
In the case where a thermal spray coating made of cermet is provided on the surface of a base member made of a metal, the coefficient of thermal expansion of the thermal spray coating is smaller than the coefficient of thermal expansion of the base member. Therefore, the thermal spray coating may peel or crack. As a result, there is a risk that the base member cannot be sufficiently prevented from being damaged.
Japanese Laid-Open Patent Publication No. 2004-277828 discloses the provision of an intermediate layer, exhibiting a coefficient of thermal expansion between those of the thermal spray coating and the base member, between the thermal spray coating and the base member as a means for preventing peeling and cracking of the thermal spray coating. In this case, however, another problem may arise such that cost increases due to an increase in the number of steps of providing an intermediate layer.