Study On Subsequent Processing And Microstructure And Properties Of Spray Deposited Gcr15 Bearing Steel

Spray forming technology has the unique advantage of short process, low cost, high production in the fabrication of materials. But there are too many controllable parameters in spray process, the parameters are interact by each other. The process of the parameters choosing is complicated, there is not complete metallurgical bonding between droplets, between droplet and interface. As a results,there are pores in the billet. These pores will bring the strong stress concentration, reduce the effective bearing area of the materials, so that to decrease the mechanical properties, it is the bottleneck of this technology spreading.GCr15 which was commonly used in bearing steel industry is employed in this paper, made use of scanning electron microscope, metallurgical microscope and Gleeble-1500D thermal simulation machine etc., study the structure and high temperature rheological behavior of spray forming GCr15 deposited preform and over spray powder, utilize heat compressing method to improve the organization and mechanical properties of GCr15 deposited preform, so as to grope the suitable subsequent processing and constitute equations.The detection of the microstructure indicated that there were some different size of pores with irregular shape, crescent shape, and nearly spherical shape in spray deposited preform which could not be seen and were filled in all the sample, and as a result lead to a lower density of deposit preform with an average density of 85.51%.An orthogonal experiment, has been used to evaluate the influence of deformation temperature, deformation rate, deformation degree and heating rate on densification efficacyY, which was comprehensive evaluated based on density, grain size and grain evenness. The results show that deformation temperature affect the densification efficacy of spray depositedGCr15 alloy obviously. The optimization deformation temperature was 850℃, deformation rate was 0.1 mm·s-1, deformation degree was 60% and heating rate was 10℃·s-1. The densification efficacy of the spray deposited preform was improved by using optimum. To be specific, the relative density increased by 12.31%, the grain size of decreased by 79.27% and the grain evenness of increased by 24.8%. GCr15 spray deposited preform occurs strain hardening and obviously dynamic recrystallization in the course of hot compression, the flow stress increases with the increase of strain rates an d decreases with the increase of temperature; the forecast of flow stress is in good agreement with the experiment, its rheological action can be described by hyperbolic function of the constitute equations accurately.