Abstract
Surface coating is an effective approach to improve cutting tool performance, and multiple or gradient coating structures have become a common development strategy. However, composition mutations at the interfaces decrease the performance of multi-layered coatings. The key mitigation technique has been to reduce the interface effect at the boundaries. This study proposes a structure design method for property-component gradient coatings based on process control. The method produces coatings with high internal cohesion and high external hardness, which could reduce the composition and performance mutations at the interface. A ZrTiN property gradient ternary nitride coating was deposited on cemented carbide by multi-arc ion plating with separated Ti and Zr targets. The mechanical properties, friction behaviors, and cutting performances were systematically investigated, compared with a single-layer coating. The results indicated that the gradient coating had better friction and wear performance with lower wear rate and higher resistance to peeling off during sliding friction. The gradient coating had better wear and damage resistance in cutting processes, with lower machined surface roughness Ra. Gradient-structured coatings could effectively inhibit micro crack initiation and growth under alternating force and temperature load. This method could be extended to similar ternary nitride coatings.
Highlights
With the rapid development of high- and ultra-high-speed cutting and dry cutting technology, and the constant emergence of new engineering materials with excellent mechanical properties, the condition of the cutting deformation zone is becoming extremely harsh [1]
Better performances are demanded of cutting tools, including hardness, strength, and heat-resistance
The coating is subjected to enormous external extrusion and shearing effects at the workpiece–coating interface, and high temperature and thermal shock at the tool–coating interface [13]
Summary
With the rapid development of high- and ultra-high-speed cutting and dry cutting technology, and the constant emergence of new engineering materials with excellent mechanical properties, the condition of the cutting deformation zone is becoming extremely harsh [1]. As an efficient and economical approach to improving the performances of existing materials [2,3,4], surface coating technologies have been rapidly developed and widely applied in coated tools [5,6,7]. The cutting area in actual cutting processes must withstand extremely high force and temperature [12], and there are intensive interactions between the tool, workpiece, and coating at two interfaces: tool–coating and workpiece–coating. Excellent comprehensive mechanical performances of Materials 2018, 11, 758; doi:10.3390/ma11050758 www.mdpi.com/journal/materials
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