Apparatus and method for machining of hard metals with reduced detrimental white layer effect

Abstract

An apparatus and a method are disclosed for reducing a thickness of a thermomechanically-affected layer on an as-machined surface of a hard metal workpiece being machined by a hard cutting tool exerting a thermomechanical load on a surface of the workpiece. The method involves reducing the thermomechanical load on the surface of the workpiece, and the apparatus includes a means for reducing the thermomechanical load on the surface of the workpiece.

1 . A method for reducing a thickness of a thermomechanically-affected layer on an as-machined surface of a hard metal workpiece being machined by a hard cutting tool exerting a thermomechanical load on a surface of the workpiece, comprising reducing the thermomechanical load.  
     
     
         2 . A method as in  claim 1 , wherein the cutting tool initially has a first temperature prior to contacting the surface of the workpiece, and wherein the thermomechanical load is reduced by cooling the cutting tool to a second temperature lower than the first temperature before the cutting tool contacts the surface of the workpiece or while the workpiece is being machined.  
     
     
         3 . A method as in  claim 2 , wherein the cutting tool is cooled by an external cooling means.  
     
     
         4 . A method as in  claim 3 , wherein the cooling means comprises at least one inert, water-free coolant.  
     
     
         5 . A method as in  claim 3 , wherein the cooling means comprises at least one cryogenic fluid.  
     
     
         6 . A method as in  claim 1 , wherein at least a portion of the thermomechanical load is a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, and wherein the thermomechanical load is reduced by reducing the component of the cutting force.  
     
     
         7 . A method as in  claim 6 , wherein the cutting tool has an inclination angle, and wherein the component of the cutting force is reduced by making the inclination angle more positive.  
     
     
         8 . A method as in  claim 6 , wherein the cutting tool has a rake angle, and wherein the component of the cutting force is reduced by making the rake angle more positive.  
     
     
         9 . A method as in  claim 4 , wherein the cutting tool has a hardness and a resistance to cracking, and wherein cooling the cutting tool with the cooling means results in an increase in the hardness or an increase in the resistance to cracking.  
     
     
         10 . A method as in  claim 1 , wherein the hard metal workpiece comprises an iron-containing alloy.  
     
     
         11 . A method as in  claim 1 , wherein the hard cutting tool is made at least in part of a material selected from a group containing a ceramic compound; a ceramic-ceramic composite; a ceramic-metal composite; a diamond-like, metal-free material; an alumina-based ceramic; a cubic boron nitride-based ceramic material; a tungsten carbide-based material; and a cermet-type material.  
     
     
         12 . A method for reducing a thickness of a thermomechanically-affected layer on an as-machined surface of a hard metal workpiece being machined by a hard cutting tool initially having a first temperature prior to contacting the surface of the workpiece, the hard cutting tool exerting a thermomechanical load on a surface of the workpiece, at least a portion of the thermomechanical load being a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising the steps of: 
 cooling the cutting tool to a second temperature lower than the first temperature before the cutting tool contacts the surface of the workpiece or while the workpiece is being machined; and    reducing the component of the cutting force.    
     
     
         13 . A method for mitigating a detrimental effect of a thermomechanical load in a machined surface of a hard metal workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool machining the workpiece, thereby forming the machined surface, comprising cooling the machined surface by a cooling means having an initial temperature in a range of about −250° C. to about +25° C.  
     
     
         14 . A method as in  claim 13 , wherein the cooling means comprises at least one stream containing a cryogenic fluid or at least one ice particle having a temperature less than about −75° C.  
     
     
         15 . A method as in  claim 13 , wherein the cooling means comprises at least one inert, water-free coolant.  
     
     
         16 . A method as in  claim 13 , wherein the hard metal workpiece comprises an iron-containing alloy.  
     
     
         17 . A method as in  claim 13 , wherein the hard cutting tool is made at least in part of a material selected from a group containing a ceramic compound; a ceramic-ceramic composite; a ceramic-metal composite; a diamond-like, metal-free material; an alumina-based ceramic; a cubic boron nitride-based ceramic material; a tungsten carbide-based material; and a cermet-type material.  
     
     
         18 . A method for mitigating a detrimental effect of a thermomechanical load in a machined surface of a hard metal workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool machining the workpiece, thereby forming the machined surface, comprising the steps of: 
 cooling the machined surface by a cooling means having an initial temperature in a range of about −250° C. to about +25° C.; and    cooling the cutting tool simultaneously by the cooling means.    
     
     
         19 . A method for mitigating a detrimental effect of a thermomechanical load in a machined surface of a hard metal workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool machining the workpiece, thereby forming the machined surface, wherein at least a portion of the thermomechanical load is a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising the steps of: 
 cooling the machined surface by a cooling means having an initial temperature in a range of about −250° C. to about +25° C.; and    reducing the component of the cutting force.    
     
     
         20 . A method as  claim 19  wherein the cutting tool has an inclination angle, and wherein the component of the cutting force is reduced by making the inclination angle more positive and the cooling means comprises at least one stream containing a cryogenic fluid or at least one ice particle having a temperature less than about −75° C.  
     
     
         21 . A method for mitigating a detrimental effect of a thermomechanical load in a machined surface of a hard metal workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool machining the workpiece, thereby forming the machined surface, wherein at least a portion of the thermomechanical load is a component of the cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising the steps of: 
 cooling the machined surface by a cooling means having an initial temperature in a range of about −250° C. to about +25° C.;    cooling the cutting tool simultaneously by the cooling means; and    reducing the component of the cutting force.    
     
     
         22 . A method as in  claim 21 , wherein the cutting tool has an inclination angle, and wherein the component of the cutting force is reduced by making the inclination angle more positive and the cooling means comprises at least one stream containing a cryogenic fluid with at least one ice particle having a temperature less than about −75° C.  
     
     
         23 . A method for machining a hard metal workpiece, whereby a thickness of a thermomechanically-affected layer on an as-machined surface of the workpiece is reduced, the workpiece being machined with a hard cutting tool initially having a first temperature prior to contacting the surface of the workpiece, the hard cutting tool exerting a thermomechanical load on a surface of the workpiece, comprising cooling the cutting tool to a second temperature lower than the first temperature before the cutting tool contacts the surface of the workpiece or while the workpiece is being machined.  
     
     
         24 . A workpiece machined by a method as in  claim 23  and characterized by an improved surface or an improved property.  
     
     
         25 . A method for machining a hard metal workpiece, whereby a detrimental effect of a thermomechanical load is mitigated in a machined surface of the workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool forming the machined surface of the workpiece, comprising cooling the machined surface by a cooling means having an initial temperature in a range of about −250° C. to about +25° C.  
     
     
         26 . A workpiece machined by a method as in  claim 25  and characterized by an improved surface or an improved property.  
     
     
         27 . A method for machining a hard metal workpiece, whereby a thickness of a thermomechanically-affected layer on an as-machined surface of the workpiece is reduced, the workpiece being machined with a hard cutting tool, the hard cutting tool exerting a thermomechanical load on a surface of the workpiece, at least a portion of the thermomechanical load being a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising reducing the component of the cutting force.  
     
     
         28 . A workpiece machined by a method as in  claim 27  and characterized by an improved surface or an improved property.  
     
     
         29 . A method for machining a hard metal workpiece, whereby a thickness of a thermomechanically-affected layer on an as-machined surface of the workpiece is reduced, the workpiece being machined with a hard cutting tool initially having a first temperature prior to contacting the surface of the workpiece, the hard cutting tool exerting a thermomechanical load on a surface of the workpiece, at least a portion of the thermomechanical load being a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising the steps of: 
 cooling the cutting tool to a second temperature lower than the first temperature before the cutting tool contacts the surface of the workpiece or while the workpiece is being machined; and    reducing the component of the cutting force.    
     
     
         30 . A method for machining a hard metal workpiece, whereby a detrimental effect of a thermomechanical load is mitigated in a machined surface of the workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool forming the machined surface of the workpiece, comprising the steps of: 
 cooling the machined surface by a cooling means having an initial temperature in a range of about −250° C. to about +25° C.; and    cooling the cutting tool simultaneously by the cooling means.    
     
     
         31 . A method for machining a hard metal workpiece, whereby a detrimental effect of a thermomechanical load is mitigated in a machined surface of the workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool forming the machined surface of the workpiece, wherein at least a portion of the thermomechanical load is a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising the steps of: 
 cooling the machined surface by a cooling means having an initial temperature in a range of about −250° C. to about +25° C.; and    reducing the component of the cutting force.    
     
     
         32 . A method for machining a hard metal workpiece, whereby a detrimental effect of a thermomechanical load is mitigated in a machined surface of the workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool forming the machined surface of the workpiece, wherein at least a portion of the thermomechanical load is a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising the steps of: 
 cooling the machined surface by a cooling means having an initial temperature having a range of about −250° C. to about +25° C.;    cooling the cutting tool simultaneously by the cooling means; and    reducing the component of the cutting force.    
     
     
         33 . An apparatus for reducing a thickness of a thermomechanically-affected layer on an as-machined surface of a hard metal workpiece being machined by a hard cutting tool exerting a thermomechanical load on a surface of the workpiece, comprising a means for reducing the thermomechanical load.  
     
     
         34 . An apparatus as in  claim 33 , wherein the hard metal workpiece comprises an iron-containing alloy.  
     
     
         35 . An apparatus as in  claim 33 , wherein the hard cutting tool is made at least in part of a material selected from a group containing a ceramic compound; a ceramic-ceramic composite; a ceramic-metal composite; a diamond-like, metal-free material; an alumina-based ceramic; a cubic boron nitride-based ceramic material; a tungsten carbide-based material; and a cermet-type material.  
     
     
         36 . An apparatus for reducing a thickness of a thermomechanically-affected layer on an as-machined surface of a hard metal workpiece being machined by a hard cutting tool initially having a first temperature prior to contacting the surface of the workpiece, the hard cutting tool exerting a thermomechanical load on a surface of the workpiece, at least a portion of the thermomechanical load being a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising: 
 a means for cooling the cutting tool to a second temperature lower than the first temperature before the cutting tool contacts the surface of the workpiece or while the workpiece is being machined; and    a means for reducing the component of the cutting force.    
     
     
         37 . An apparatus for mitigating a detrimental effect of a thermomechanical load in a machined surface of a hard metal workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool machining the workpiece, thereby forming the machined surface, comprising a means for cooling the machined surface by at least one stream of a coolant having an initial temperature in a range of about −250° C. to about +25° C.  
     
     
         38 . An apparatus as in  claim 37 , wherein the at least one stream contains a cryogenic fluid or at least one ice particle having a temperature less than about −75° C.  
     
     
         39 . An apparatus as in  claim 37 , wherein the stream contains at least one inert, water-free coolant.  
     
     
         40 . An apparatus for mitigating a detrimental effect of a thermomechanical load in the machined surface of a hard metal workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool machining the workpiece, thereby forming the machined surface, wherein at least a portion of the thermomechanical load is a component of the cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising: 
 a means for cooling the machined surface by at least one stream containing at least one inert, water-free coolant having an initial temperature in a range of about −250° C. to about +25° C.;    a means for cooling the cutting tool simultaneously by at least another stream containing at least one inert, water-free coolant; and    a means for reducing the component of the cutting force.    
     
     
         41 . An apparatus for machining a hard metal workpiece, whereby a thickness of a thermomechanically-affected layer on an as-machined surface of the workpiece is reduced, the workpiece being machined by a hard cutting tool initially having a first temperature prior to contacting the surface of the workpiece, the hard cutting tool exerting a thermomechanical load on a surface of the workpiece, comprising a means for cooling the cutting tool to a second temperature lower than the first temperature before the cutting tool contacts the surface of the workpiece or while the workpiece is being machined.  
     
     
         42 . A workpiece machined by an apparatus as in  claim 41  and characterized by an improved surface or an improved property.  
     
     
         43 . An apparatus for machining a hard metal workpiece, whereby a detrimental effect of a thermomechanical load is mitigated in a machined surface of the workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool forming the machined surface of the workpiece, comprising a means for cooling the machined surface by a stream of a fluid having an initial temperature in a range of about −250° C. to about +25° C.  
     
     
         44 . A workpiece machined by an apparatus as in  claim 43  and characterized by an improved surface or an improved property.  
     
     
         45 . An apparatus for machining a hard metal workpiece, whereby a thickness of a thermomechanically-affected layer on an as-machined surface of the workpiece is reduced, the workpiece being machined by a hard cutting tool exerting a thermomechanical load on a surface of the workpiece, at least a portion of the thermomechanical load being a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising a means for reducing the component of the cutting force.  
     
     
         46 . A workpiece machined by an apparatus as in  claim 45  and characterized by an improved surface or an improved property.  
     
     
         47 . An apparatus for machining a hard metal workpiece, whereby a thickness of a thermomechanically-affected layer on an as-machined surface of the workpiece is reduced, the workpiece being machined by a hard cutting tool initially having a first temperature prior to contacting the surface of the workpiece, the hard cutting tool exerting a thermomechanical load on a surface of the workpiece, at least a portion of the thermomechanical load being a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising: 
 a means for cooling the cutting tool to a second temperature lower than the first temperature before the cutting tool contacts the surface of the workpiece or while the workpiece is being machined; and    a means for reducing the component of the cutting force.    
     
     
         48 . An apparatus for machining a hard metal workpiece, whereby a detrimental effect of a thermomechanical load is mitigated in a machined surface of the workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool forming the machined surface of the workpiece, comprising: 
 a means for spraying the machined surface with at least one stream of a fluid having an initial temperature in a range of about −250° C. to about +25° C.; and    a means for spraying at least one other stream of the fluid simultaneously on the cutting tool.    
     
     
         49 . An apparatus for machining a hard metal workpiece, whereby a detrimental effect of a thermomechanical load is mitigated in a machined surface of the workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool forming the machined surface of the workpiece, wherein at least a portion of the thermomechanical load is a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising: 
 a means for spraying the machined surface with at least one stream of a fluid having an initial temperature in a range of about −250° C. to about +25° C.; and    a means for reducing the component of the cutting force.    
     
     
         50 . An apparatus for machining a hard metal workpiece, whereby a detrimental effect of a thermomechanical load is mitigated in a machined surface of the workpiece, the thermomechanical load being exerted on a surface of the workpiece by a hard cutting tool forming the machined surface of the workpiece, wherein at least a portion of the thermomechanical load is a component of a cutting force, the component being applied in a direction normal to the surface of the workpiece, comprising: 
 a means for spraying the machined surface with at least one stream of a fluid having an initial temperature in a range of about −250° C. to about +25° C.;    a means for spraying at least one other stream of the fluid simultaneously on the cutting tool; and    a means for reducing the component of the cutting force.