Design And Preparation Of Febased Amorphous Alloy Coating And Its Properties

Compared with traditional coal-fired boliler, circulating fluidized bed bolier has a series of advantages, such as coal adaptability, pollution control, low-cost, load regulation performance, easy-to-ash utilization. It is widely used in electric power, petroleum, chemical, and waste disposal areas, but the serious erosion wear of the four-tube affected the normal operation of the unit. An effective way to solve this problem is to prepare one kind of ablation-resistant coating on the surface layer. Amorphous alloys have high strength, high hardness, wear resistance, corrosion resistance and other unique and outstanding performance, using spray technology to prepare amorphous coatings can put them into the engineering applications of wear-resistant protection, to a certain extent, ease the problems caused by erosion wear of the four-tube.In this study, the development process of amorphous alloys and factors of glass-forming ability were analyzed, the experience of formulation rules of amorphous alloy preparation were learned, and Fe-based cored wires with high glass forming ability were designed and prepared. FeCrMoCBSi amorphous coating and Fe-based low-alloy amorphous coating were deposited by high velocity arc spraying technology. The phase structure, microstructure, micro hardness, thermal stability, Oxidation resistance, Corrosion resistance, bond strength and abrasive wear resistance of the coatings were characterized. Effect of Si-B substition on property of FeCrMoCBSi amorphous coating, effect of Nickel RE on property of Fe-based low-alloy amorphous coating and effect of B and alloy content on property of Fe-based low-alloy amorphous coating were discussed. The erosion resistance of the Fe-based low alloy coatings in 30°, 90°erosion angle under different temperature were analyzed. Some of main experimental results and conclusions are listed as follows.The amorphous phase content of FeCrMoCBSi coating and Fe-based low alloy coating were 65.5%, 70.2%. The coatings have a typical layered structure and a good compactness. The micro-hardness of the coatings are in excess of 1300HV0.1, the bond strength are all greater than 30Mpa. The crystalline transition of the two coatings are 853K and 855K. The two amorphous coatings are all have good resistance to oxidation at 650℃compared with Fe based Boron carbide coating and Fe based Chromium carbide coating. The relative wear-resistant property of the FeCrMoCBSi coating is 5.1 times by GCr15 bearing ball at 450℃. The relative wear-resistant property of the Fe based low alloy coating is 5.2 times by GCr15 bearing ball at 500℃.The amorphous phase content of the FeCrMoCBSi amorphous coatings changed from 47% to 65.1% with the adjustment of silicon-boron, the micro-hardness of the coatings increase with the increase of amorphous content. The adjustment of silicon-boron did not affect the crystallization temperature of FeCrMoCBSi amorphous coatings. The coating has high amorphous phase content showed good abrasive wear resistance. Additions of Nickel RE promote the amorphous phase content of the Fe-based low alloy coating, the L-A2 coating has amorphous phase content of 76.5%, the crystallization transition temperature of the coating is also increased, and the coating showed higher hardness and better abrasive wear resistance.The amorphous phase content of the Fe-based low alloy coatings changed from 71.1% to 74.2% with the adjust of boron and alloy content, the coating with 16% atom fraction of boron added has the highest of amorphous phase content, the micro-hardness of the coatings increase with the increase of amorphous content. The changes of the amount of boron and alloy did't affect thermal stability of the Fe-based low alloy coatings.The coating has high content of amorphous phase has shown good resistance to ersion wear in a variety of test conditions. The erosion weight loss of Fe-based low-alloy amorphous coatings in 90°erosion angle is lager than in 30°erosion angle under the same condition. The erosion weight loss of Fe-based low-alloy amorphous coating showing different weight loss under different temperatures. The surface of Fe-based low-alloy amorphous coatings appearance clear-cutting, furrow-shaped scar and slight brittleness of pit-like spalling after eroded by the 30°angle test, brittle fracture and pit-like peeling appearance after eroded by the 90°angle test.