Study On The Microstructure And Property Of High Strength Martensitic Iron-based Alloy Formed By Laser

In the light of the characteristics of the strength and toughness of Cr-Ni martensitic stainless steel,three kinds of Fe-17Cr-3Ni-0.8Si martensitic iron-based alloy powders with different contents of C and B elements were designed.By adjusting the content of C and B elements in powder,a laser rapid-shaping layer is prepared on the substrate,and use the Olympus microscope,X-ray diffractometer(XRD),scanning electron microscope(SEM),rockwell hardness tester,electro-hydraulic servo universal testing machine movement,vertical universal friction and wear testing machine and other equipment on microstructure and mechanical properties of laser forming were characterized.The results are as follows:(1)when the content of C and B elements is 0.12%~0.15% and 0.1% ~0.15%,the phase of the laser-shaped sample has the main phase of martensite and there is Cr C phase,and the secondary phase particles segregate at grain boundary.The hardness of the laser-forming sample is 53.2HRC~59.3HRC,the tensile strength is 1806MPa~1856MPa,the elongation is 2%~2.3%.When the loading coefficient is 0.4 and the frequency is 20 Hz,the fatigue fracture life of laser formed specimens is more than 105 times.(2)when the content of C and B elements are less than or equal to 0.08%,there are different lamellar martensite structures and a small amount of ferrite in the sample.The hardness of the laser-shaped sample is 29.2HRC~32.7HRC,the tensile strength is 1406MPa~1443MPa,and the elongation is 7.3%~10.4%.When the loading coefficient is 0.4 and the frequency is 20 Hz,the fatigue fracture life of laser formed specimens is more than 105 times.(3)When the contents of C and B elements are 0.25%~0.35% and ?0.08%,there are austenite,martensite and Cr23C6 phases in the samples.The hardness of the laser-shaped sample is 25.4HRC~29.1HRC,the tensile strength is 762MPa~884MPa,and the elongation rate is 3.6%~4.6%.When the loading coefficient is 0.4 and the frequency is 20 Hz,the maximum fatigue fracture life of laser formed specimens is 86708 times.