Reaerach For Wear Hardfacing Alloy Of High Hardness And High Crack Resistance

At the moment, it obtains fine performance hardfacing alloys mainly byadding complex alloys such as ferrovanadium, ferrotungsten, ferromolybdenum,ferrochromium etc, but it’s the disadvantage of reducing the cost practice for thealloys’ high prices; Or using the simple Fe-Cr-C alloy system which can have ahigh hardness hardfacing alloy, but it has bad crack resistance because of lots ofcarbon. So it’s important to develop a new hardfacing alloy for engineeringapplication with high hardness, high crack resisitance and high wear resisitance.Based on the principle of reducing the cost and using simple alloy system, adoptingshielded metal arc welding plan to research a new Fe-Cr-B system wear hardfacingalloy of high hardness and high crack resistance only by the addition offerrochromium and ferroboron.First, using orthogonal test method to optimize coating mineral compositions，through experimental investigations find the impact of different mineralcompositions to the surfacing electrode’s slag detachability, slag coverage andhardfacing alloy’s crack resistance. It obtains an excellent coating formula withcombination property.Tested and analysed hardfacing alloy with Rockwell hardness tester,microhardness tester, optical microscope, scanning electron microscope(SEM),enery disperse spectroscopy(EDS), direct-reading spectrometer, X-ray diffractomeretc. The results show that graphite has little affect of hardfacing layer hardness, butit worse the crack resisitance; with the addition of right amount REMg can refinehardfacing layer’s structure and increase the crack resistance, the hardfacing alloymorphology chang from columnar crystals and dendrite to equally distributedisometric crystal. With the increase of boron, the hardness and abrasive resistancefirst increase then decrease. The microstructure of hardfacing alloy is major ofFe-Cr phrase,M23(C,B)6, B0.7Fe3C0.3, Fe3C and M7C3phrase, in which the boridewith chrysanthemum or herringbone shape wrapped up Fe-Cr phrase, and have amatrix of martensite and austenite.Using MM-200type fraction abrasion testing machine and SEM discussed theabrasion mechanism of the hardfacing alloy. In the wear processes, the boride with chrysanthemum or herringbone shape block the press-in of hard particle andmicroscopic cutting movement. At the later stage of wear, the boride fractured atimpact load of abrasive particle and it goes to the lower material.The paper developed a hardfacing alloy which has no crack with a hardness of65HRC, and it also has high wear resistance, can be applicable to high stress ofabrasive wear occasions, so it can be widely used in mining machine,cementindustry,coal machine etc.