The influence of some process parameters of sputter ion plating on the deposition of tungsten on chemical vapour deposition (CVD) grown diamond wafers has been investigated. Direct deposition will give stressed films with bad adhesion. The level of stress can be reduced by moving the substrate away from direct ion bombardment. Further improvement in adhesion has been achieved following treatment with oxygen ions prior to depositing tungsten. Poorly CVD grown diamond wafers have disintegrated following coating with tungsten at high sputtering rate.