A Combined Process of Thermal Spraying and Casting for Fixing Hard Wear-Resisting Coating on the Internal Surface of the Cast Products

本研究的目的是克服内表面喷涂的困难。通过试验研究，开发了一种在铸件缸体壁等小孔内表面固定硬质耐磨涂层的新工艺。热喷涂技术与铸造技术巧妙结合。核心部件先前通过热喷涂工艺涂上硬质耐磨涂层，然后在铸造模具中构建。只去掉核心部件后，铸件孔的内表面就保留了所需的涂层，如WC-12%Co涂层。采用高速氧燃料火焰（HVOF）喷涂工艺生产的WC-12%Co涂层硬度在Hv900以上，为铝合金铸件表面提供了有效的耐磨保护。虽然HVOF喷涂不能将WC-12%Co涂层直接沉积在树脂覆膜砂芯表面，但采用补充铝衬底涂层使其成为可能。在剪切模式下，WC-12%Co涂层对AC4B铝合金铸件的粘接强度为5 ~ 10mpa。采用ni -10%铝合金覆盖层、铸型预热、ni -10%铝合金覆盖层表面粗化等方法，将其提高到10-20 MPa。对Ni-10%Al、Cu-10%Al和Zn三种复盖材料进行了试验。结果表明，ni -10%铝合金覆盖层对增强WC-12%Co涂层与AC4B铸件的结合力最为有效。

The aim of this research is to overcome the difficulty of internal surface spraying. Experimental investigational were carried out to develop a new technique in order to fix the hard wear-resisting coating on the internal surface of small holes such as cylinder wall in the cast products.Thermal spraying technology and casting technology were skillfully combined. The core components, previously coated hard wear-resisting coating by applying thermal spraying process, were builts in a casting mold. The desired coating such as WC-12%Co coating is left on internal surface of the hole on the cast product after removing just the core component from it. WC-12%Co coating produced by the process of high velocity oxygen-fuel flame(HVOF)spraying has a hardness above Hv900, therefore, it provides an effective wear-resisting property for protecting the surface of aluminum alloy cast products. Although HVOF spraying could not deposit the WC-12%Co coating directly on the surface of resin coated sand core, adoption of the supplemental aluminum underlay coating made it possible. Adhesive strengh of the WC-12%Co coating to the AC4B aluminum alloy cast products is 5-10 MPa in shear mode. It was improved to 10-20 MPa by applying overlay coating of Ni-10%Al alloy, preheating of the casting mold and by roughening the Ni-10%Al alloy overlay coating surface. Three kinds of overlay coating materials Ni-10%Al, Cu-10%Al and Zn were experimented. It was revealed that the overlay coating of Ni-10%Al alloy was most effective to strengthen the adherence between WC-12%Co coating and the cast AC4B body.