ZHOU Li
,
SUN Dale
,
LIU Changsheng
,
WU Qiong
钢铁研究学报(英文版)
The fatigue behavior of high speed steel (HSS) roll materials for hot rolling was researched under watercooling conditions by laser impacting. The microstructure of HSS sample and the morphologies of fatigue samples were observed by scanning electron microscope. The phase structure was detected by XRD. The morphology of situ oxide scale was observed by optical microscope, and the expansion coefficient was measured by TGA. The experiment results indicate that the cracks come into being at the carbidematrix interface, but there are no cracks in the matrix after many times of laser impacting treatment, for the situ sample taken from the fractured roll surface, big carbides are more sensitive to the fatigue, and peel off prior to small ones. The relevant fatigue mechanisms are also discussed.
关键词:
high speed steel;fatigue;laser impacting;stress concentration;carbide
DONG Danyang
,
LIU Changsheng
,
ZHANG Bin
钢铁研究学报(英文版)
Based on the Miedema′s formation heat model for binary alloys and the Toop′s asymmetric model for ternary alloys, the formation heat, excess entropy, and activity coefficients of silicon ranging from 1 900 K to 4 100 K in the FeSiC melt formed during the laser cladding high silicon coatings process were calculated. The results indicated that all values of lnγ0Si, εCSi, ρSiSi and ρCSi are negative in the temperature range and these values increase as the temperature increases. And all values of εSiSi and ρSiCSi are positive and these values decrease with increasing temperature. The isoactivity lines of silicon are distributed axisymmetrically to the incident laser beam in the melt pool vertical to the laser scanning direction. And the isoactivity lines of silicon in the front of the melt pool along the laser scanning direction are more intensive than those in the back of the melt pool. The activity of silicon on the bottom of the melt pool is lower than that in the effecting center of laser beam on the top surface of the melt pool and it may be the important reason for the formation of the silicides and excellent metallurgical bonding between the laser cladding coating and the substrate.
关键词:
laser cladding;silicon steel;high silicon content coating;thermodynamic calculation;Miedema′s formation heat model
