A Microstructure Comparison of TiN with a Cr Metallic Interlayer and Boride Layers Formed on AISI 304 Steel: Wear Properties

High performance machining of hard-to-cut materials is a challenge. There are two major categories of most widely used hard-to-cut materials: (1) hardened tool steels for dies and molds fabrication as well as (2) aerospace materials such as Ni-based super-alloys and Ti-based alloys. Likewise, wear and corrosion are major causes of machinery downtime and material loss in industry contributing to decreased profits. Since wear is a surface phenomenon, the use of hard coatings can be an efficient solution, allowing the substrate to maintain its impact resistance and the coating can be produced to withstand wear, corrosion, abrasions and thermal loads while at the same time reducing costs by using diminutive amounts of hard materials [1-11]. A proposed solution consists of developing a hard, dense, wearand corrosion-resistant coating formed on a surface with certain affinity in fracture toughness, as well as the creation of a dislocation interface that prevents the propagation of the corrosive medium to the substrate and the propagation of micro-cracks [10, 11]. In particular, boriding is a recognized surface treatment for achieving high surface hardness (up to 2000 HV) and low coefficient of friction while improving the corrosion and erosion resistance and is being increasingly used in many industrial applications. Likewise, PVD (physical vapour deposition) is the one of the ways of their deposition onto tool steels substrate. The low deposition temperature is significant advantage of this method. However, these coatings show relatively low adhesion to substrate. Improvement of the adhesion may be achieved by modifying the substrate or adjusting physical proper-ties of the coating to the substrate as much as possible in order to achieve similar mechanical properties like hardness. The hard TiN (Titanium Nitride) coatings are also used for coating machine tools such as drills, lathe tool inserts, stamps and punches, and expensive forming tools such as injection molds for plastics. In the present study, the microstructure of three coating