Study On Fe-Cr-C Hardfacing Alloys With High Carbon Contents

Three fields are primarily studied in this paper as below:1. The formula of hardfacing electrodes with high carbon contents is studied. The effects of alloy elements to processing properties of electrodes are investigated.2. The effects of carbon to microstructure and mechanical property of hardfacing layer are researched.3. The orientation control of the primary carbides in the hardlayer is studied.Titanium-calcium type of electrode coating are selected by studying typical formula of coatings and transfer efficiency of carbon.Effects of carbide to welding process are investigated by controlling carbon content. With increasing carbon content welding process get worse. When carbon content is lower the hardfacing layer has no crack; when it is increased the transverse cracks appear at first and the longitudinal cracks appear with the increasing of the carbon contents. Welding process get worse with an increase in chromium content and smooth bead turn to be discontinuous.Effects of carbon to macrohardness and abrasive resistance of hardfacing layer are studied by adding the graphite to the electrode coatings gradually. Several conclusions can be got in this paper by X-ray phase analysis, SEM analysis, electron energy spectrum analysis, TEM analysis, microhardness analysis and metallographic observation: The quantity and volume of the primary carbide increase gradually with increasing carbon content; The volume of the eutectic carbide becomes larger with an increase in carbon contents and the eutectic carbides grow around primary carbides; The further the eutectic carbides are from primary carbides the denser they are-, Primary carbides and eutectic carbides isolatedly distribute on the base metal; Thehardness of hardfacing layer increases with increasing carbon content. But when exceeding 6%, the increase get slow; The relationship between carbon content and abrasive resistance was investigated by abrasion test. The abrasive resistance increases with an increase in carbon content between 3.14% and 5.16% .Two methods are used to study law of directional growth for primary carbides:Firstly, increase of the carbon contents of hardfacing layer.Secondly, raise degree of supercooling when welding.These two kinds of methods can both make carbide grow directly, but has some difference. The volume of primary carbides get larger when carbon content is increased but get smaller when raising cooling speed. It can be concluded by abrasive test that good abrasive resistance can be got by raising degree of supercooling based on increasing carbon content in hardfacing layer properly.