Cermet alloy containing nitrogen

A drill formed of a cermet comprising hard dispersed phases mainly composed of one member selected from the group consisting of a nitride compound of titanium and a carbo-nitride compound of titanium, said cermet alloy further comprising at least one metal selected from the group consisting of groups IVa, Va and VIa of the periodic table excluding titanium, and binder metal phases selected from the group consisting of nickel and cobalt, wherein

• said hard dispersed phases include a metal atom group containing titanium and a nonmetal atom group containing nitrogen,
• the amount of said titanium contained in said metal atom group is at least 0.5 and not more than 0.95 as an atomic ratio,
• the amount of said nitrogen contained in said nonmetal atom group is at least 0.1 and not more than 0.7 as an atomic ratio,
• said hard dispersed phases comprise a fine grained portion having a mean grain size within the range of at least 0.2 .mu.m and not more than 0.6 .mu.m and a coarse grained portion having a mean grain size within the range of at least 1 .mu.m and not more than 3 .mu.m,
• the volume ratio of said fine grained portion to said coarse grained portion is at least 0.3 and not more than 3, and wherein
• the proportion of said binder metal phases contained in said cermet, is at least 5 percent by weight and not more than 30 percent by weight.

A drill formed of cermet, comprising a head section including cutting means for cutting a work piece and a shank section carrying said head section, said cermet comprising hard dispersed phases mainly composed of one member selected from the group consisting of a nitride compound of titanium and a carbo-nitride compound of titanium, said cermet alloy further comprising at least one metal selected from the group consisting of groups IVa, Va and VIa of the periodic table excluding titanium, and binder metal phases selected from the group consisting of nickel and cobalt, wherein

• said hard dispersed phases include a metal atom group containing titanium and a nonmetal atom group containing nitrogen,
• the amount of said titanium contained in said metal atom group is at least 0.5 and not more than 0.95 as an atomic ratio,
• the amount of said nitrogen contained in said nonmetal atom group is at least 0.1 and not more than 0.7 as an atomic ratio,
• the proportion of said binder metal phases contained in said cermet is at least 5 percent by weight and not more than 30 percent by weight, said hard dispersed phases of said cermet forming said head section comprise a fine grained portion with a mean grain size of at least 0.2 .mu.m and not more than 0.6 .mu.m and a coarse grained portion with a mean grain size of at least 1 .mu.m and not more than 3 .mu.m,
• the volume ratio of said fine grained portion to said coarse grained portion is at least 0.3 and not more than 3, and wherein
• said hard dispersed phases of said cermet forming said shank portion are formed substantially by grains having a grain size within the range of at least 0.2 .mu.m and not more than 0.6 .mu.m.

A sintered hard alloy drill comprising a head section for cutting a workpiece and a shank section carrying said head section, wherein

• said head section is formed of a cermet comprising hard dispersed phases mainly composed of one member selected from the group consisting of a nitride compound of titanium and a carbonitride compound of titanium, said cermet alloy further comprising at least one metal selected from the group consisting of groups IVa, Va and VIa of the periodic table excluding titanium, and binder metal phases selected from the group consisting of nickel and cobalt, wherein
• said hard dispersed phases include a metal atom group containing titanium and a nonmetal atom group containing nitrogen,
• the amount of said titanium contained in said metal atom group is at least 0.5 and not more than 0.95 as an atomic ratio,
• the amount of said nitrogen contained in said nonmetal atom group is at least 0.1 and not more than 0.7 as an atomic ratio,
• said hard dispersed phases comprise a fine grained portion with a mean grain size of at least 0.2 .mu.m and not more than 0.6 .mu.m and a coarse grained portion with a mean grain size of at least 1 .mu.m and not more than 3 .mu.m,
• the volume ratio of said fine grained portion to said coarse grained portion is at least 0.3 and not more than 3,
• the proportion of said binder metal phases contained in said cermet is at least 5 percent by weight and not more than 30 percent by weight, and wherein
• said shank portion is integrally joined with said head portion, and formed of WC cemented carbide containing cobalt.