Study On Fatigue Failure Analysis For Hardfacing Layer

The roller press machine is an important equipment in the cement industry,which is mainly used for crushing ore, grinding raw material and grinding clinker. Inorder to improve the wear resistance of the surface of the roller press machine, theroller surface is often deposited by the hardfacing layer. Because the disbonding ofwear layer resulted from fatigue is one of the important reasons for the roller pressfailure, the study on influencing factors of the generation and expansion of the fatiguecracks between the hardfacing layer and the substrate is very meaningful to improvethe anti-fatigue performance of the hardfacing layer.By self-shielded welding, using three self-shielded welding wires （KSW-615,KSW-626, KSW-645） to prepare three different types of surfacing layer: the basemetal+high chromium cast iron hardfacing layer、transition layer+high chromiumcast iron hardfacing layer、titanium carbide hardfacing layer. The main microstructuref the transition layer is austenite, the average Rockwell hardness and the measuredmicrohardness of which are27and343; The bottom microstructure of the basemetal+high chromium cast iron hardfacing layer is the hypoeutectic microstructureincluding Austenite and eutectic organization, the upper microstructure of which is thehypereutectic organization including carbides （（Fe,Cr）₇C₃and Cr₇C₃）) and eutecticmicrostructure. The Rockwell hardness of the bottom and upper of the surfacing layerare55.8and61, the measured carbide microhardness of which are793.5; Because ofthe limited influence of the transition layer with High Cr and high Mn, the mainmicrostructure of transition layer+high chromium cast iron hardfacing layer is theeutectic microstructure, the Rockwell hardness of the bottom and upper of thesurfacing layer are60and61, the measured carbide microhardness of which is797;The main microstructure of titanium carbide hardfacing layer are the particulatetitanium carbide and austenite, the average Rockwell hardness and the measuredmicrohardness of which are56and712.Titanium carbide hardfacing layer has good anti-fatigue performance, which hasthe highest fatigue strength of three types of hardfacing layer, when the loading force is increased to2700KN, the number of cycles is8000, and there are disbonding cracksgenerated in the hardfacing layer. The microstructure of the surfacing layer are finetitanium carbide particulates and austenite, these fine titanium carbide particles isdispersion-like distributed in the austenitic matrix, so that the surfacing layer has goodplasticity and toughness and can withstand high stress load.When the loading force is1350KN, the number of cycles is6000, and the basemetal+high chromium cast iron hardfacing layer near the fusion line has disbondingcracks generated. When the loading force is600KN, the number of cycles is16000,and there has no disbonding crack generated near the fusion line, which alsoshows that the high chromium cast iron hardfacing layer is not suitable for large load.The transition layer+high chromium cast iron hardfacing layer is the worstsurfacing layer for anti-fatigue performance among three types of hardfacing layer,when the loading force is1350KN, the number of cycles is2000, and there has nodisbonding cracks generated near the fusion line. The main microstructure of thehardfacing layer is the hypereutectic microstructure and has poor plasticity andtoughness, which is very prone to disbonding cracks generated near the fusion line bythe role of external forces. Therefore, when the high chromium cast iron hardfacinglayer is chose, selected reasonable transition layer is very important in order toimprove the anti-fatigue performance of the hardfacing layer. According to thedifference of hardingfacing layers, reasonable transition layer can be selected.