热处理工艺对硬质合金表面金刚石薄膜附着性能的影响

Effects of Heat-Treatment on the Adhesive Strength of Diamond Films Coated on the Cemented Carbide Substrates

文章针对提高硬质合金刀具金刚石涂层结合力问题,提出了一种热处理和酸处理相结合的预处理工艺,详细研究和分析了800~1 000℃范围内,热处理温度变化与硬质合金刀具表面形貌、金刚石涂层质量、涂层与刀具间附着力之间的关系。热处理工艺显著降低了生长过程中钴对金刚石涂层石墨化的催化作用,进一步提高了碳化钨颗粒的比表面积及金刚石二次形核密度,得到的金刚石涂层晶粒尺寸及压应力较小。过高的热处理温度虽然可以细化基体表面,增加基体与金刚石涂层之间的"机械锁合"作用,但预处理过程中残留在基体表面的深坑却不利于金刚石涂层附着力的提高,在外力的作用下容易在深坑附近产生微裂纹。实验结果显示,在氩气气氛中,900℃时热处理的硬质合金基体表面生长的金刚石涂层质量和附着力最佳。

In this paper, to improve the adhesive strength of diamond films for the cemented substrates before depositing process, a new approach combined with heat-treatments and acid treatments was investigated. Relations between heat-treatments and surface morphologies, quality of diamond films and the adhesive strength were analyzed within the temperature range of 800-1 000℃. Heat treatment on the cemented substrate was an effective method to improve the adhesive strength for diamond films. With the heating process, large tungsten particles can be refined to small size which can enhance the ＂interlock functions＂ between diamond films and the substrate, and improve the density of secondary nucleation. The redundant metal cobalt was removed effectively to prevent the catalytic actions, which may cause the transformation from diamond to graphite. However, the adhesive strength was decreased with high temperature heating process subject to the holes left on the substrate surface. Results show that the samples heated at 900~C owned the strongest adhesive strength and least compressive stress for diamond films.