Ti-W-Si-Al Based Coated Tungsten Carbide End Mills In Cutting Hardened Steel Ⅲ

In last part we know that tungsten carbide end mills with (Ti,W,Si,Al)N coating film have the least tool wear at speed of below 3.33 m/s in cutting hardened steel. Here in this part we explain the superior quality of (Ti,W)N coating film.

1. Introduction

Hardened steels used for dies or molds are widely cut as a substitute for grinding. Polycrystalline cubic boron nitride (cBN) compact tools are used for cutting hardened steels, due to their higher hardness and higher thermal conductivity. However, in milling, major tool failure of cBN readily occurs by fracture because cBN has poor fracture toughness. Coated cemented tungsten carbide is an effective tool material for milling hardened steels because it has good fracture toughness and wear resistance. The physical vapor deposition (PVD) method is a widely used coating technology because of its lower treatment temperature, namely 470 K -870 K.

Recently, it has become possible to cut hardened steels with (Ti,Al)N-coated tungsten carbide cutting tools. However, as machine parts are often cut at higher cutting speeds for mass production, tool materials must have excellent fracture toughness and wear resistance. A titanium/tungsten-based coating film, namely (Ti,W)N coating film, has been developed. Titanium/tungsten-based coating film exhibits a superior critical scratch load.

(To be continued. This article is divided into several parts. Here is part 3. For part 2 please refer to http://news.chinatungsten.com/en/tungsten-information/80790-ti-10484; for part 4, please refer to http://news.chinatungsten.com/en/tungsten-information/80792-ti-10486)

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