Effect Of B Content And Q&P Process On Microstructure And Mechanical Properties Of High-boron Iron-based Wear-resistant Alloys

Traditional wear-resistant materials mainly use carbide as the wear-resistant framework,but there are problems such as insufficient toughness and wear resistance.Based on this,this study proposes a high-boron iron-based wear-resistant alloy with higher hardness and better stability of the boride as the wear-resistant framework and high strength and toughness martensite as the matrix.It is a new type of wear-resistant material that uses boron as the main alloy element to replace chromium,molybdenum,nickel and other precious alloy elements.It has the advantages of low production cost and good forming processability.However,due to the continuous network distribution of boride in the alloy structure,the matrix is severely cracked,resulting in poor impact toughness of the alloy,which is also not conducive to the wear resistance of the alloy.Improved the impact toughness of the alloy mainly by changing the distribution of boride and increasing the volume fraction of retained austenite in the matrix structure of the alloy.This study uses methods such as changing the boron content in the alloy and performing Q&P process on the alloy to improve the impact toughness and wear resistance of the alloy.The boron content in the alloy is 1.6wt%(1#),1.9wt%(2#)and 2.2wt%(3#),respectively.Based on the study of its as-cast microstructure and mechanical properties,the influence of Q&P process on the microstructure and mechanical properties of the alloy is clarified.The results show that the as-cast microstructure of samples 1#,2# and 3# consist of ferrite,martensite,retained austenite and boride.The borides are distributed in a continuous network,mainly Fe2 B and Fe23(B,C)6.The volume fractions of boride in 1#,2# and 3# as-cast samples were 21.3%,26.6% and 29.7%,respectively,and the volume fractions of residual austenite were 10%,9.8% and 11.8%,respectively.After Q&P heat treatment,the boride in the alloy is still Fe2 B and Fe23(B,C)6.There is no ferrite in the structure,but the secondary martensite appears.The boron compounds in samples 1# and 2# showed obvious network disconnection,and the sample 3# was not obvious due to the higher boron content.With the increase of boron content,the hardness of as-cast samples increased from 59.3HRC to 65.5HRC,and the impact toughness decreased from 3.8J to 2.4J.When the austenitizing temperature is 1050℃,the austenitizing holding time is 2h,and the carbon partition temperature is 400℃.The hardness of samples 1#,2#,and 3# is 56.1HRC,59.2HRC,and 61.5HRC,respectively,and the impact toughness is 7.5J,6.3J,and 5.9J,respectively.The volume fraction of retained austenite is 17.4%.,14.7%,and 15.9%,respectively.The wear resistance of the samples was significantly improved after heat treatment.The wear resistance of 3# sample is the best,which is 4.9 times that of NM500.The wear resistance of 1# sample is the lowest,which is 3.1 times that of NM500.