High‐Temperature Erosion and Corrosion Measurement of Thermally Sprayed Materials

Abstract

World steel production will probably increase by up to 20 % in the next 10 years. [1] To meet the market demands regarding price, quality, and environmental protection, steel manufacturers have continuously to optimize their production processes. Quality and productivity are increased through activities in research and development. These include waste reduction, improvement of plant disposability, and long-term management concepts.High-velocity abrasion and other mechanical forces attack the heat exchanger tubes in steel plants and power plants. [2] In waste incinerators, chemical plant, and biomass combusting plants, aggressive media provide additional modes of degradation. [3] Owing to the operating conditions, boilers are subject to fireside corrosion and erosion, resulting in tubewall thinning and premature failure. [4,5] One way of protecting boiler tubes against failure by tribochemical strain is to use surface coatings with specific properties. Thermal spraying is a suitable process for the application of such coatings, preferably in composite layers that combine an economically simple buffer layer and a functional surface layer. [5,6] Table 1 shows the main corrosive gases and their concentration as used in standard experiments to define the hightemperature corrosion of metals and alloys in aggressive gas atmospheres. [7] Gas compositions were selected on the basis of real waste incineration atmospheres. The differences are caused by the composition of waste in the reference plants (municipal waste, [8] industrial waste, [10] and ¹specialª waste [9] with high contents of plastics and rubber).The corrosion behavior of 2.25Cr-1Mo-steel was investigated in HCl-and SO 2 -enriched atmospheres at 500 C by Spiegel. [8] The experiments in HCl-enriched atmosphere showed that the main mechanism of corrosion is active oxidation. The addition of up to 1000 ppm SO 2 gas to the HCl-containing atmosphere had no particular effect on the corrosion phenomena. No formation of sulfates or sulfites was observed. As typical of active oxidation, only layers of Fe 3 O 4 and Fe 2 O 3 were found on the surface.Numerous materials such as unalloyed, low-alloyed, alloyed, high-alloyed, and super alloy steels were studied under the operating conditions of waste incinerators at 530± 640 C by Mayerhuber and Cerjak. [9] All these materials showed high corrosion rates. The corrosion attack under these conditions led to thick, multi-layered, porous, and poorly adherent corrosion products. The published laboratory tests reveal that Ni-or Co-based alloys have higher corrosion resistance than high-alloyed steels. NiCrBSi coatings applied by APS atmospheric plasma spraying (APS) were tested in several corrosive atmospheres (HCl±O 2 ±N 2 , SO 2 ±O 2 ±N 2 , and HCl±SO 2 ±O 2 ±N 2 ) with and without H 2 O. [7,11,12] It turned out that the HCl±H 2 O±O 2 ±N 2 gas mixtures are more corrosive than the others.As the corrosive atmospheres with H 2 O are more similar to real conditions in waste incinerators, it was necessary to investigate the influence...

Use of plasma spray technology for deposition of high temperature oxidation/corrosion resistant coatings – a review

“…Cha and Wolpert [78] conducted high-temperature erosion and corrosion tests of thermally spray coatings on 15Mo3 and 13CrMo44 base materials. The coatings were Ni-based materials like Colmonoy 62 (NiCrFeBSi) and NiCrBSi/WC and Co-based material T800 fabricated by thermal spray processes like HVOF, flame sprayed and sintered (FS/sinter) and air plasma spray (APS).…”

High-temperature erosion of Fe-based coatings reinforced with cermet particles

“…One of the most widespread protection approaches is the application of a thermally sprayed coating. 6,12,13 Commonly, borides, 14 cermets 6,15 and stellites, 4,16 as well as nickel-based 8,10,17,18 and iron-based 13,19,20 alloys are applied as coating materials. The last group of alloys is gaining increasing attention because of their good mechanical properties 21-24 and their relatively low price.…”