New technique for determining temperature distribution in cemented carbide cutting tools

Abstract

A new technique has heen developed which allows the temperature distribution developed in cemented carbide inserts during metal cutting to be observed. The technique uses a series of iron- and iron-silicon-bonded carbides; each hinder type transforms to austenite at a characteristic temperature during metal cutting, subsequently forming a transformation product which appears as a heat-affected zone (HAZ) when metallographic sections are etched in nital and viewed between crossed polarizers or under dark-field illumination. Temperature maps were then constructed by tracing the boundary of each HAZ. The technique was used to study the effect of TiN coatings on tool temperatures. When cutting plain-carhon steel En8 (080A40) or Cr--Ni--Mo steel En24 (817M40), tool temperatures were reduced by TiN coatings; this may be because the chip/tool contact length was reduced when using coated inserts. When cutting grey cast iron, tool temperatures were similar for TiN-coated and uncoated inserts because the chip tool contact lengths were identical for both tool types.