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Print[Ferro-alloys.com]CHINESE scientists working at the University of Western Australia have developed a new composite that is wear-resistant under high temperatures, and can be used for applications such as boilers in power plants.
The new Iron-Sialon ceramic matrix composite was developed from ferro-silicon alloy and commercial-grade industrial alumina powders by reaction sintering under a nitrogen atmosphere.
“Most thermal power plants use circulating fluid bed boilers,” materials scientist Dr Jingzhou Yang says.
“In China, Australia and … other countries, power supply mainly relies on coal firing which requires high temperature wear-resistant linings and components.
“We undertook this research to develop a new, more wear-resistant ceramic matrix composite.
“The currently used alumina-based ceramic linings [are] low cost but their wear resistance, fracture resistance and thermal shock resistance are not good enough.”
As a result, he says, power plant maintenance schedules include lengthy downtime to repair worn equipment, reducing the stability and reliability of the power supply.
He says the team developed a composite consisting of continuous-phase Sialon ceramic and discrete phase iron alloy.
“The ductile alloy phase could improve the fracture resistance and thermal shock resistance of the ceramic matrix and make the composite exhibit good wear resistance,” he says.
“The methodology is called in situ nitridation-reaction sintering.
“We use very common and cheap industrial alumina and ferro-silicon alloy powders as raw materials, and sinter them at a high temperature of 1400-1700 degrees in nitrogen … for several hours.
“Then the alumina will transform to the more wear-resistant ceramic of Sialon.
“Iron alloy particles distribute in Sialon matrix discontinuously, which leads to the good fracture resistance and thermal shock resistance of this Sialon matrix composite.”
Dr Yang says the new iron alloy particle-reinforced Sialon matrix composite has better erosion-wear resistance than alumina ceramic at a comparable manufacturing cost.
“Fe–Sialon composites showed better erosion wear resistance than the control material of alumina ceramic at 1200?C, although having much lower density and slightly lower bending strength,” he says.
Dr Yang says it could be used as new generation wear-resistant linings in equipment for power generation as well as sectors such as mining exploration and processing, thereby lengthening equipment life and saving millions of dollars.
He says further research is indicated.
“We are planning to further study the fracture resistance and thermal shock resistance, and understand why this composite shows good performances containing good wear resistance,” he says.
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