电火花加工在聚晶金刚石耐磨带成形中的工艺适配与效率提升研究

Process adaptability and efficiency enhancement of electrical discharge machining for polycrystalline diamond hardbanding profiling

摘要:

针对聚晶金刚石耐磨带类超硬复合材料机械磨削成形时大余量去除效率低、砂轮磨损大等问题，围绕电火花加工在聚晶金刚石耐磨带成形中的工艺适配与效率提升开展实验研究。区别于放电与机械作用在同一加工区同步进行的复合加工方式，也不同于采用旋转轮电极完成材料去除的电火花磨削，本文将电火花加工与机械磨削设置为前后独立工序，提出电火花粗加工、60目粗磨整形和400目精磨修整分阶段进行余量分配的加工方法。以胎体金属包镶热稳定聚晶金刚石（TSP）块的环形聚晶金刚石耐磨带为对象，首先分别对胎体包镶材料和TSP材料电火花加工响应进行分析，再开展复合材料表面电火花加工参数优选，最后开展耐磨带电火花成形与机械磨削修整，并与纯机械磨削、纯电火花加工进行工艺对比评价。结果表明：纯机械磨削表面粗糙度为2.63 μm，但质量去除率仅为0.20625 g/h，加工效率受限；电火花加工质量去除率可达1.23053 g/h，具有较高去除效率，虽然加工表面粗糙度为16.62 μm，难以直接满足表面质量要求，但在机械磨削修整进行小余量去除后，能使质量去除效率较纯机械磨削提高160.2%，同时将表面粗糙度控制在2.92 μm，接近纯机械磨削水平。研究表明，电火花加工经参数适配后可有效用于聚晶金刚石耐磨带类超硬复合材料高效率成形，并可为深井钻杆接头聚晶金刚石耐磨带加工提供工艺参考。

Abstract:

To address the low bulk stock-removal efficiency and severe grinding-wheel wear encountered during the mechanical grinding and profiling of superhard composites such as polycrystalline diamond （PCD） hardbanding， an experimental study was conducted into the process applicability and efficiency enhancement of electrical discharge machining （EDM） for PCD hardbanding profiling. Unlike hybrid processes in which electrical discharge and mechanical actions occur simultaneously within the same machining zone， and electrical discharge grinding using a rotating wheel electrode， the proposed method arranges electrical discharge machining and mechanical grinding as sequential， independent operations and allocates the machining allowance across three stages： EDM roughing， profile grinding with a 60-grit wheel， and finish grinding with a 400-grit wheel. The investigated PCD hardbanding consisted of thermally stable polycrystalline diamond （TSP） blocks embedded in a metal matrix. Firstly， the EDM responses of the metal-matrix material and TSP material were characterized separately. The EDM parameters for machining the composite surface were then optimized. Finally， the hardbanding was profiled by EDM and subsequently finished by mechanical grinding， and the combined process was comparatively evaluated against pure mechanical grinding and pure EDM alone. The results showed that pure mechanical grinding produced a surface roughness of 2.63 μm， but its mass removal rate was only 0.20625 g/h， resulting in limited machining efficiency. EDM achieved a mass removal rate of up to 1.23053 g/h， demonstrating substantially higher stock-removal efficiency. Although the EDM-processed surface exhibited a roughness of 16.62 μm and could not directly satisfy the surface-quality requirement， subsequent mechanical grinding with a small finishing allowance increased the overall mass removal efficiency by 160.2% compared with pure mechanical grinding， while reducing the surface roughness to 2.92 μm， a level close to that achieved by pure mechanical grinding. These results demonstrate that， after appropriate parameter optimization， EDM can be effectively applied to the high-efficiency profiling of superhard composites used in PCD hardbanding. The proposed process provides a technical reference for machining PCD hardbanding on drillpipe tool joints used in deep-well drilling.