Study Of Fe-based Surfacing Material Reinforced By In-situ Synthesized Hard Particles

The welding materials for hardfacing usually have much carbon and valuable alloyelements in modern industry. With the precipitation of hard alloying carbides insurfacing layer, iron-based coating could be strengthened. However, some weaknesseswere found when these hardfacing materials were extensively used, such as coating’spoor toughness and carbide’s instability at high temperature. These problems have badeffect on the wear resistance of surfacing layer which greatly reduces device’s servicelife. Therefore, the development of surfacing material which has low carbon andalloying content, high hardness and excellent wear resistance has very importantapplication value.In this study, we first designed to strengthen Fe-based coating by in-situ synthesizednitrides through tungsten nitrogen arc welding. The effect of different elements contenton nitrides’ synthesis was researched when nitrogen was the main component of theprotect gas. The particles’ precipitation behavior and strengthening mechanism werealso studied in this work. Deposited metal’s microstructure and performance were testedby modern analytical methods. The results showed that precipitates’ quantity and sizeincreased with the rise of nitrogen’s proportion in mixed gas and boron’s content. Themaximum microhardness of hardfacing metal was998HV. There were three kinds ofprecipitates in deposited layer: TiN with square or dendritic shape, TiB2with blockshape and (Ti、V)N with granular shape. In particles’ precipitation process, TiB2and VNboth nucleated on TiN’s surface, then grew up to TiB2-TiN and (Ti、V)N compositereinforced particles. They didn’t continuously distribute in the matrix which lead togood toughness and crack resistance of deposited metal.On this basis, we tried to develop a new type of self-shielded flux cored wire whichused nitrogen in air and nitrogen fixation metal in core as the reactants in synthesisreaction. The deposited metal containing carbonitride particles was manufactured byopen arc welding. The surfacing layer was consisted of martensite, carbonitrideprecipitations and residual austenite. The main component of the precipitations wasTi(C、N) and VN which could mutually dissolved to become a new type of MX binarycarbonitrides. The hardness of deposited alloy was more than58HRC since the effect ofprecipitation particles. Abrasion testing showed that the abrasive wear resistance of nitrogen-alloying deposited metal was superior to the surfacing alloy of high chromiumcasting.