Enhancing machining quality and tool wear resistance in nickel-based superalloy GH4169 deep hole boring: an optimized boring tool with additional guide pad strategy

Nickel-based superalloy GH4169, due to its high strength, hardness, and toughness, poses a severe challenge to the improvement of deep-hole boring processing quality. In response to this, an optimized BTA boring tool quipped with an additional third tungsten carbide guide pad strategy was independently designed. A tool-workpiece contact mechanics model is developed to elucidate the enhancement mechanism of the three-guide-pad layout on the dynamic stiffness of the tool system. The machining quality of the deep hole and the wear resistance of the tool were studied through boring experiments. The research findings indicate that the layout of three guide pads constructs a more complete stiffness matrix, which enhances the dynamic stiffness of the tool by utilizing multi-directional force balance and obtains more stable support constraints. The flank face wear width of the optimized BTA boring tool is 51 µm smaller than that of the conventional tool. The cutting insert and guide pads of the optimized tool show less severe wear. Compared with the conventional BTA boring tool, the optimized BTA boring tool shows approximately 0.45 mm smaller in hole straightness, 0.054 mm smaller in hole diameter runout, and 0.8 µm smaller in surface roughness, exhibiting superior cutting performance. The shear and extrusion of the tool induce a "gradient effect" in the bore wall surface layer, with nonlinearly varying residual compressive stress on the surface. The findings are significantly important for addressing the issue of poor machining quality in boring large depth-to-diameter ratio deep hole structures of difficult-to-machine metal materials and can provide valuable insights into understanding the boring mechanism, preventing tool failure, and controlling machining quality.