Raising demands in industry lead to the request of better and enhanced functional surfaces, also on rolls parts in paper producing machines. Due to the higher usage of post-consumer recycled fibers on paper machines the run ability and machine cleanliness become a major issue. On one hand the contaminates called stickies can be responsible for sheet brakes, holes in the paper, web picking etc. On the other hand more sand containing waste paper enhances the impact on roll surfaces in operation. In this paper the different stickies (micro / macro / primary / secondary) and their impact on the paper production will be explained and the development to avoid stickies and contaminations together with high wear resistant coatings on roll surfaces in the paper machinery will be shown. Therefore a comparison of different materials and technologies regarding surface energy and peel force measurements are explained. Together with results of a pilot scale blade test rig the results in the market regarding anti stick properties wear resistance and corrosion resistance of the developed layer stack designs will be introduced.

This paper discusses the different types of rolls used in paper machines, the functions and performance required of them, and recent improvements achieved with the aid of thermal spray coatings. It presents examples showing how metal and ceramic coatings applied by HVOF and plasma spraying have reduced operating expenses and extended roll life by stabilizing and improving various surface properties.

This paper discusses the role of thermal spraying in the development of carbon-fiber rollers for web processing equipment. It provides a detailed review of the roller design covering key sizing and selection criteria with emphasis on roller surface performance. It describes the manufacturing process, which includes the application of a 30-35 mm HVOF-sprayed WC layer, and the tests used to verify that the coating meets design requirements and that the roller will provide stable rotation at ultrahigh speeds, sufficient traction force, and high abrasion resistance. A version of the HVOF-coated carbon-fiber roller discussed in this paper is installed in a slitter-winder, running smoothly at speeds up to 4800 rpm with no abrasive wear.

Carbon-fiber-reinforced plastic (CFRP) rolls are increasingly employed in manufacturing equipment due to their light weight, high stiffness, and low inertia and flexure. These rolls, however, are rarely used without a surface coating due to their lack of wear resistance and gripping properties. This paper examines the effects of thermal shock on an experimental carbide-type cermet coating deposited by atmospheric plasma spraying on a CFRP test roll. After thermal shock testing, coating cracks and peeling were observed. The underlying cause was determined and an improved coating, a nickel-base composite with high thermal shock resistance, has been developed, tested, and put to use in a papermaking line, where the rolls have been maintenance-free for more than four years.

In the sieve section of a paper producing machine, where the formation of paper occurs, a polyethylene sieve is guided over a set of ceramic blades to remove the water in the paper slurry. These sieves are running with velocities of 70 km/h and more. The high velocities lead to defects in the tissue structure of the sieve as well as on the blades. Moreover the presence of high abrasive particles like kaolin and carbonates in the paper slurry as well as its corrosive characteristics enforce the material wear. Present solutions include bulk ceramic blades but they cause defects on the sieves and they are quite expensive. New solutions are desired where these bulk ceramic blades can be replaced by intelligent coating systems that on one hand exhibit an extraordinarily high wear resistance but can minimize the wear of the PE sieve on the other hand. The presentation gives first results obtained by different types of ceramic and cermetic coating systems manufactured by thermal spray technology.

The demand for better paper qualities and for higher speed of the paper web requires a constant technological development of the existing calendering process. An important factor in modern calendering is the heated metal roll. Its surface has an important influence on the gloss and the smoothness of the paper. During operation these rolls are heated to temperatures of up to 200°C. Additionally, the rolls are exposed to severe abrasive wear by fine hard filler materials and to corrosion by the moisture of the paper. The SUMECAL coating systems - especially developed for calender rolls - surpass the hard chromium platings by far regarding the scratch and wear resistance and demonstrate better calendering properties. Paper text in German.

Some applications of high velocity oxygen fuel (HVOF) flame sprayed WC cermet coatings in paper mills are summarized. The WC cermet sprayed coating is one of the most widely used in the thermal spray industry. HVOF sprayed WC cermet coatings have such excellent physical and chemical properties that they are extensively employed in the industrial field. Typical properties for example, are wear resistance, high stress rotating bending or rolling contact fatigue strength, frictional characteristics, wettability for aqueous agent, non picking or non adhesive property against foreign material, thermal conductivity, mirror finished surface property and so on. They are derived from the compact, denser microstructure, containing fine-sized hard WC particles, high bond strength onto substrate. These characteristics obtained by HVOF sprayed WC cermet coatings are utilized to improve the surface functions of machine parts which are installed mainly in the press department, drying department, size press, calender department and finishing department of paper mills. In this study, examples of some application of WC cermet coatings in several types of rolls in paper mills are introduced.