High hardness silicon nitride sintered bodies

Claim 2

A high hardness silicon nitride sintered body for use as a bearing material prepared from a mixture including 3-7 wt% Y 2 O 3 , 1-4 wt% MgO and 1-2 wt% ZrO 2 as sintering aids, said sintered body consisting essentially of 10-50 wt% α-Si 3 N 4 with the remainder being β-Si 3 N 4 , wherein said sintered body has a Knoop hardness of not less than 15.5 GPa, a bending strength of not less than 100 kg/mm 2 and a rolling fatigue life of not less than 1×10 7 cycles.

Claim 3

A high hardness silicon nitride sintered body according to claim 1, wherein said α-Si 3 N 4 is present in an amount of 15-45 wt% and said sintered body has a Knoop hardness of not less than 16.0 GPa.

Claim 4

A high hardness silicon nitride sintered body according to claim 1, wherein said α-Si 3 N 4 is present in an amount of 26-40 wt% and said sintered body has a Knoop hardness of not less than 16.5 GPa.

Claim 5

A high hardness silicon nitride sintered body according to claim 1, wherein said sintered body has a Young's modulus of not less than 290 GPa.

Claim 6

A high hardness silicon nitride sintered body according to claim 1, wherein said sintered body has a Young's modulus of not less than 295 GPa.

Claim 7

A high hardness silicon nitride sintered body according to claim 1, wherein said sintered body has a Young's modulus of not less than 300 GPa.

Claim 8

A hot isostatic pressed high hardness silicon nitride sintered body for use as a bearing material prepared from a mixture including 3-7 wt% Y 2 O 3 , 1-4 wt% MgO and 1-2 wt% ZrO 2 as sintering aids, said sintered body consisting essentially of 15-45 wt% α-Si 3 N 4 with the remainder being β-Si 3 N 4 , wherein said sintered body has a Knoop hardness of not less than 16.0 GPa, a bending strength of not less than 100 kg/mm 2 and a rolling fatigue life of not less than 1×10 7 cycles.

Claim 9

A hot isostatic pressed high hardness silicon nitride sintered body for use as a bearing material prepared from a mixture including 3-7 wt% Y 2 O 3 , 1-4 wt% MgO and 1-2 wt% ZrO 2 as sintering aids, said sintered body consisting essentially of 15-45 wt% α-Si 3 N 4 with the remainder being β-Si 3 N 4 , wherein said sintered body has a Knoop hardness of not less than 16.0 GPa, a bending strength of not less than 100 kg/mm 2 and a rolling fatigue life of not less than 1×10 7 cycles.

Claim 10

A hot isostatic pressed high hardness silicon nitride sintered body according to claim 7, wherein said α-Si 3 N 4 is present in an amount of 26-40 wt% and said sintered body has a Knoop hardness of not less than 16.5 GPa.

Claim 11

A hot isostatic pressed high hardness silicon nitride sintered body according to claim 7, wherein said sintered body has a Young's modulus of not less than 290 GPa.

Claim 12

A hot isostatic pressed high hardness silicon nitride sintered body according to claim 7, wherein said sintered body has a Young's modulus of not less than 295 GPa.

Claim 13

A hot isostatic pressed high hardness silicon nitride sintered body according to claim 7, wherein said sintered body has a Young's modulus of not less than 300 GPa.

Claim 14

A hot isostatic pressed high hardness silicon nitride sintered body for use as a bearing material consisting essentially of 10-50 wt% α-Si 3 N 4 with the remainder being β-Si 3 N 4 , said body being formed by a method comprising: mixing Si 3 N 4 powder with 3-7 wt% Y 2 O 3 , 1-4 wt% MgO and 1-2 wt% ZrO 2 powders to form an initial mixture; pulverizing said initial mixture to form a resultant mixture; drying said resultant mixture to form a powder; shaping said powder to form a shaped powder compact; and sintering said shaped powder compact in an N 2 atmosphere at a temperature of about 1600-1720° C. for about 1-3 hours to form said sintered body; wherein said sintered body has a Knoop hardness of not less than 15.5 GPa, a bending strength of not less than 100 kg/mm 2 and a rolling fatigue life of not less than 1×10 7 cycles.

Claim 15

A hot isostatic pressed high hardness silicon nitride sintered body for use as a bearing material consisting essentially of 10-50 wt% α-Si 3 N 4 with the remainder being β-Si 3 N 4 , said body being formed by a method comprising: mixing Si 3 N 4 powder with 3-7 wt% Y 2 O 3 , 1-4 wt% MgO and 1-2 wt% ZrO 2 powders to form an initial mixture; pulverizing said initial mixture to form a resultant mixture; drying said resultant mixture to form a powder; shaping said powder to form a shaped powder compact; and sintering said shaped powder compact in an N 2 atmosphere at a temperature of about 1600-1720° C. for about 1-3 hours to form said sintered body; wherein said sintered body has a Knoop hardness of not less than 15.5 GPa, a bending strength of not less than 100 kg/mm 2 and a rolling fatigue life of not less than 1×10 7 cycles.

Claim 16

A hot isostatic pressed high hardness silicon nitride sintered body for use as a bearing material consisting essentially of 10-50 wt% α-Si 3 N 4 with the remainder being β-Si 3 N 4 , said body being formed by a method comprising: mixing Si 3 N 4 powder, predominantly consisting of 96% by weight α-Si 3 N 4 , with 3-7 wt% Y 2 O 3 , 1-4 wt% MgO and 1-2 wt% ZrO 2 powders to form an initial mixture; pulverizing said initial mixture to form a resultant mixture; drying said resultant mixture to form a powder; shaping said powder to form a shaped powder compact; pressureless sintering said shaped powder compact to form a sintered body; and hot isostatic pressing said sintered body in an N 2 atmosphere at a pressure of 400 atm and a temperature of about 1530-1750° C. to form a hot pressed sintered body; wherein said hot isostatic pressed sintered body has a Knoop hardness of not less than 15.5 GPa, a bending strength of not less than 100 kg/mm 2 and a rolling fatigue life of not less than 1×10 7 cycles.

Claim 17

A hot isostatic pressed high hardness silicon nitride sintered body for use as a bearing material consisting essentially of 10-50 wt% α-Si 3 N 4 with the remainder being β-Si 3 N 4 , said body being formed by a method comprising: mixing Si 3 N 4 powder, predominantly consisting of 96% by weight α-Si 3 N 4 , with 3-7 wt% Y 2 O 3 , 1-4 wt% MgO and 1-2 wt% ZrO 2 powders to form an initial mixture; pulverizing said initial mixture to form a resultant mixture; drying said resultant mixture to form a powder; shaping said powder to form a shaped powder compact; pressureless sintering said shaped powder compact to form a sintered body; and hot isostatic pressing said sintered body in an N 2 atmosphere at a pressure of 400 atm and a temperature of about 1530-1750° C. to form a hot pressed sintered body; wherein said hot isostatic pressed sintered body has a Knoop hardness of not less than 15.5 GPa, a bending strength of not less than 100 kg/mm 2 and a rolling fatigue life of not less than 1×10 7 cycles.