Effect of MQL on wear behavior of various coated tools in hobbing (Fundamental experiments using fully coated tools)

This paper deals with the effect of minimal quantity lubrication (MQL) on tool life (flank wear), crater wear of various coated high-speed steel tools and finished surface roughness in hobbing. Experiments were conducted by simulation hobbing by fly tool cutting on a milling machine. The results are summarized as follows. (1) When changing the kinds of coating films, a TiAlN-coated tool showed the longest tool life. Tool lives of almost of the tested coated tools obtained with MQL system are longer than those obtained by dry cutting, and the wear reduction effect by MQL was recognized. Especially, an AlCrSiN-coated tool showed the tool life more than twice compared with dry cutting. (2) It is assumed that the crater wear is caused by the delamination of the coting film, and the crater wear in the case of MQL occurs earlier than that in dry cutting. Both in dry cutting and MQL, the crater wear does not appear on the AlCrSiN-coated tool, which is effective for the crater wear. (3) In all of tested coated tools, the finished surface roughness obtained with MQL is smaller than that obtained by dry cutting. When using TiAlN- and AlCrSiN-coated tools, the surface roughness reduction effect by MQL is large. The TiAlN-coated tool showed the smallest surface roughness of the four kinds of coated tools. (4) From the viewpoints of tool life, crater wear and finished surface roughness, TiAlN- and AlCrSiN-coated tools are suitable for MQL system.