Dry machining of soft metal-modified aluminum castings with carbon-coated tools

Abstract

Additions of small but effective amounts of one or more of bismuth, indium, lead and/or tin to a silicon-containing aluminum casting alloy markedly improves the dry machinability of a casting made from the modified alloy. But dry machining of such castings is synergistically improved by the use of cutting tools with cutting surfaces coated with microcrystalline diamond or diamond-like carbon coatings. The use of such carbon-coated tools enables remarkable improvement in dry machinability even at reduced levels of the soft metal in the alloy.

1 . A method of making an aluminum alloy article comprising: 
 making a casting of the article from an aluminum alloy comprising, by weight, 5% to 18% silicon, a small amount up to about 2% by weight of one or more machining lubricity-imparting elements selected from the group consisting of bismuth, indium, lead and tin; the casting containing a dispersed phase containing the lubricity-imparting element; and    machining a surface of the casting with a cutting tool to remove cast material without the use of a machining fluid, the cutting tool being a tungsten carbide cutting tool having a surface coated with diamond-like carbon or microcrystalline diamond.    
     
     
         2 . A method of making an aluminum alloy article comprising: 
 making a casting of the article from an aluminum alloy comprising, by weight, 5% to 18% silicon, 1.3% max iron, 0.2% max copper or 2% to 5% copper, 1.3% max magnesium, 0.6% max manganese, about 0.03% to about 2% of one or more machining lubricity-imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum; the casting containing a dispersed phase containing the lubricity-imparting element; and    machining a surface of the casting with a cutting tool to remove cast material without the use of a machining fluid, the cutting tool being a tungsten carbide cutting tool having a surface coated with diamond-like carbon or microcrystalline diamond.    
     
     
         3 . The method of making an aluminum alloy article as recited in  claim 2  comprising making a casting of the article from an aluminum alloy comprising, by weight, 5% to 13% silicon, 1.3% max iron, 0.2% max copper, 1.3% max magnesium, 0.6% max manganese, about 0.03% to about 2% of one or more machining lubricity-imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum.  
     
     
         4 . The method of making an aluminum alloy article as recited in  claim 2  comprising making a casting of the article from an aluminum alloy comprising, by weight, 5% to 13% silicon, 1.3% max iron, 2% to 5% copper, 1.3% max magnesium, 0.6% max manganese, about 0.03% to about 2% of one or more machining lubricity-imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum.  
     
     
         5 . The method of making an aluminum alloy article as recited in  claim 2  comprising making a casting of the article from an aluminum alloy comprising, by weight, 16% to 18% silicon, 1.3% max iron, 4% to 5% copper, 0.4% to 0.65% magnesium, 0.1% max manganese, about 0.03% to about 2% of one or more machining lubricity-imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum.  
     
     
         6 . The method of making an aluminum alloy article as recited in  claim 2  comprising making a casting of the article from an aluminum alloy comprising, by weight, 5% to 7.5% silicon, 1% max iron, 2% to 5% copper, 0.5% max magnesium, 0.6% max manganese, about 0.03% to about 2% of one or more machining lubricity-imparting elements selected from the group consisting of bismuth, indium, lead and tin, and aluminum.