Ultrafine Tungsten Carbide Grain Growth Under Laser Action Mechanism Research

The laser welding technology is used to realize the connection between the ultra-fine cemented carbide material and the steel to obtain the heat affected zone of the cemented carbide.The post-weld samples are processed in combination with cutting,polishing,etc.and image information is acquired using an optical microscope.The microstructure and composition distribution of the heat affected zones were observed and analyzed by scanning microscopy.The paper systematically studied the microstructure of the heat affected zone of ultra-fine cemented carbide and steel laser welding,the distribution of WC grains under different welding speeds and the growth mechanism of abnormal large WC grains.1.Ultra-fine cemented carbide WC-TaC-TiC-Co and stainless steel 316 L were connected by laser welding in the experiment.With a welding power of 3.5k W and welding speeds of 0.015m/s,0.020m/s and 0.025m/s,the welding of steel and cemented carbide substrates was obtained under the three process conditions.2.The microstructure and grain size of the ultra-fine cemented carbide WC-TaC-TiC-Co heat affected zones were studied.The results show that under the same welding power,as the welding speed increases,the grain size grows significantly compared to the area where the uppermost part is not affected by the heat input.3.Analyzed the mechanism of abnormal large WC grain growth.Through the observation of the microstructure and microstructure of the abnormally large WC grains,it can be concluded that a single abnormally large WC grain can be seen that the shape is relatively regular and the edges are relatively smooth,showing a triangular and elongated shape.The regular anomalous large WC grains are surrounded by a large number of regular small grains;the WC grains with small grain size surround the abnormally large WC grains and form a large area containing a large number of pores.