For high-efficiency grinding of difficult-to-cut materials such as titanium and nickel alloys, a high porosity is expected and also a sufficient mechanical strength to satisfy the function.However, the porosity increase is a disadvantage to the mechanical strength. As a promising pore forming agent, alumina bubbles are firstly induced into the abrasive layer to fabricate porous cubic boron nitride(CBN) wheels. When the wheel porosity reaches 45%, the bending strength is still high up to 50 MPa with modified orderly pore distribution. A porous CBN wheel was fabricated with a total porosity around 30%. The grinding performance of the porous composite-bonded CBN wheel was evaluated in terms of specific force, specific grinding energy, and grinding temperature, which were better than those of the vitrified one under the same grinding conditions. Compared to the vitrified CBN wheel, clear straight cutting grooves and less chip adhesion are observed on the ground surface and there is also no extensive loading on the wheel surface after grinding.
In order to develop the high-efficiency and precision machining technique of Ti Cp/Ti–6Al–4V particulate reinforced titanium matrix composites(PTMCs), high-speed grinding experiments were conducted using the single-layer electroplated cubic boron nitride(CBN) wheel and brazed CBN wheel, respectively. The comparative grinding performance was studied in terms of grinding force, grinding temperature, grinding-induced surface features and defects. The results display that the grinding forces and grinding temperature obtained with the brazed CBN wheel are always lower than those with the electroplated CBN wheel. Though the voids and microcracks are the dominant grinding-induced surface defects, the brazed CBN wheel produces less surface defects compared to the electroplated wheel according to the statistical analysis results. The maximum materials removal rate with the brazed CBN wheel is much higher than that with the electroplated one. All above indicate that the single-layer brazed CBN super-abrasive wheel is more suitable for high-speed grinding of PTMCs than the electroplated counterpart.
Plunge grinding experiments were carried out on CSS-42L stainless steel with the white fused alumina wheel.The grinding forces were measured with variations in accumulated material removal volume.Then the morphological features of worn grinding wheel were analyzed by optical microscopy and the grinding temperatures were measured with a thermocouple.For comparison,C45 steel was ground under the same conditions.The results indicated that the grinding forces of CSS-42L were at least twice that of C45 steel.When the accumulated removal volume overcame 375mm^3,strong adhesion was found between the abrasives and workpiece CSS-42L.Nevertheless,adhesion was hardly found after 800mm^3 workpiece C45 steel was removed.In order to enhance the machining property of CSS-42L,a brazed CBN wheel was incorporated into the grinding of CSS-42L,and the grinding forces and temperatures were found significantly decreased,whose maximum decreasing amplitude was about 70%and 80%,respectively.
Yang ChangyongXu JiuhuaFu YucanDing WenfengSu Honghua
