around a cylinder or the roll coating is produced by using a flexible mat which is fixed to the roll frame by melting by using induction laser or any other suitable heating these methods are described in detail in the valmet fi patent no 70 273 and in the fi patent appln 853544 when the coating is produced by spraying it is carried out by spraying of two powder components which are a carbide and binder material and b matrix metal with respect to the properties of moistening and surface tension the coating is close to the properties of granite which has been traditionally used in the roll concerned the long term operating quality of the carbide coating is ensured by the high wear resistance produced by the high hardness 1100 hv and by the good resistance to corrosion based upon the alloying both of these factors retain the microporosity and surface roughness which are essential in view of the detaching of the web the original level of microporosity can be regulated by means of the parameters of the coating process the carbide coating will also withstand the alterations predictable in future paper machine conditions which are corrosion strain and higher temperatures filler contents and increasing linear loads the coating will also endure situations of thermal shock moreover the invention will be illustrated by means of the following examples and the accompanying figure on the.