Improvement in tool life of coated high speed steel drills using the activated reactive evaporation process

Abstract

Type M-10 high speed steel drills of diameter 0.25 in were coated with TiC and TiN using the activated reactive evaporation process. The coated drills were tested by drilling holes into plates of AISI 4150 steel of thickness 1 in at a hardness level of 300 HB. The speed used was 900 rev min -1 and the feed rate was 0.007 in rev -1. For comparison, uncoated and the standard black-oxide-coated drills were also tested using the same conditions. The average number of holes to failure was seven for uncoated drills, 33 for black-oxide-coated drills and 141 for the TiC- and TiN- coated drills. These results show that the TiC- and TiN-coated drills have tool lives of 20 times that of uncoated drills and 4.2 times that of black-oxide-coated drills under these test conditions. Torque and thrust measurements were made during the drilling test of same steel plates at 770 rev min -1 and a feed rate of 0.008 in rev -1 at Lockheed Company of California, Burbank. The TiC- and TiN-coated drills showed 15%-18% less thrust, 10%-23% less torque and eight to ten times the tool life of uncoated drills under these conditions. They also showed 15%-18% less thrust and 2.5 to three times the tool life in relation to the black-oxide-coated drills.