Effect Of Ti And N On Microstructure And Properties Of Austenite High Chromium Cast Iron

High chromium white cast iron has strong wear resistance,which is extensively used in various fields of industrial production.Some mechanical parts,such as rolls and puncher guide plate,are used in hostile environments such as high temperatures,high pressures,and chills.The general high-chromium wear-resistant cast iron materials are prone to martensite transformation in the high and low temperature alternating environment,which leads to volume expansion,causing cracks on the surface of mechanical components and increase the material wear rate.Therefore,the development of high-chromium cast iron materials with pure austenite matrix,which possesses excellent mechanical properties and abrasive resistance,has realistic practical significance for the components used in such environments.The raw materials used in this study were austenite hypereutectic high-chromium cast iron.Studies were done through metallurgical microscope,hardness test and impact toughness test,abrasion resistance test,XRD,SEM and other analytical instrument to explore the influence of heat treatment process and different titanium,nitrogen addition on the high chromium cast iron microstructure,mechanical properties and abrasion resistance.The conclusions are the following:(1)The experimental HCCI materials(3.33%C,33%Cr)were quenched at 950、1000、1050、1100°C for 2h and tempered at 260°C for 2h.The austenite in the microstructure didn’t transform into martensite,so that its hardness was improved a little.It has a higher hardness value of 47.5 HRC when quenched at 1000°C.When the temperature increased,the abrasion loss of the material is gradually reduced.The abrasion resistance is better when quenched at 1050°C.And the abrasion loss is decreased to about 39.5%of the as-cast sample.(2)Compared with the absence of Ti and N,the addition of appropriate amounts of Ti and N,the microstructure of high-chromium cast iron is significantly refined and the number of carbides is gradually increased.The long-grained primary carbides are gradually finely divided,which make its hardness and impact toughness significantly improved.(3)After experimental comparison and analysis,it was determined that 1.2%Ti+0.2%N is the preferred distribution ratio.The hardness of the high chromium cast iron under this composition was 49.3HRC,and the impact toughness was 4.49 J/cm~2.Compared to high chromium cast iron without adding Ti and N,the hardness increased7 HRC and the impact toughness increased 49.2%,and the wear resistance also increased significantly.The abrasion loss is 7.44%of the high-chromium cast iron material without adding Ti and N,displaying excellently good wear resistance.(4)When Ti and N were not added,the wear mechanism of hypereutectic high-chromium white cast iron was mainly adhesive wear.The types of fractures were brittle cleavage fracture.With the appropriate addition of Ti and N,the wear mechanism changes to abrasive wear,and in the meanwhile,the fracture type changes to quasi-clear cleavage fracture.