CTLR VECTORED 2 ACR'S TO PREVENT LOSS OF SEPARATION AT SAME ALT.

Narrative

THE FLT DEPARTED BUF AT XX27 LCL FOR AN UNEVENTFUL FLT UNTIL ARRIVING IN THE CHICAGO AREA. WE WERE TALKING TO ORD APCH CTL WHEN HE ISSUED A CLRNC TO DEPART PAPPI INTXN (OBK 077/16) HDG 180 DEGS AND MAINTAIN 6000'. APPROX 1 MIN LATER HE TOLD US TO TURN LEFT 150 DEGS AND DSND TO 5000'. I REPEATED THE CLRNC AND SET 5000' IN THE ALT ALERT WINDOW. THE F/O SET 150 DEG HDG. AT APPROX 5300' I NOTICED TFC AT 2:30 THAT APPEARED TO BE ABOUT OUR ALT; AND 5-7 MI. I ALERTED THE F/O AND NOTED THAT HE APPEARED TO BE HDG IN OUR DIRECTION. HE AGREED AND WITHIN THE NEXT 10 SECS AND IN ORDER; THE OTHER ACFT FLASHED HIS LNDG LIGHTS; NOTING THAT HE SAW US. HIS RWY TURN OF LIGHTS WERE ALREADY ON; AND THIS INDICATED TO ME THAT THIS WAS AN LGT. APCH CTL TOLD US TO 'LEVEL AT 6000' AND TURN LEFT 090 DEGS.' I REPLIED WE WERE ALREADY AT 5000' TFC IN SIGHT; AT WHICH POINT HE TOLD LGT Y TURN LEFT. (I DIDN'T CATCH THE HDG.) A COMPANY HAS BUSTED HIS ALT. LGT Y TURNED LEFT (N) AT THAT TIME AND STATED HE HAD US IN SIGHT. ORD APCH CTLR THEN GAVE US A HDG OF 180 DEGS AGAIN; TO WHICH I REPEATED THE CLRNC AND ADVISED HIM 5000' WAS OUR ASSIGNED ALT. WE WERE THEN GIVEN AN APCH CLRNC TO RWY 27R (G/S OUT) APCH AND CONTACT TWR 118.1 AT TAFFS. AT TAFFS I WAS UNABLE TO GET ANY RESPONSE ON 118.1; SO I SWITCHED TO 120.75 AND RECEIVED CLRNC TO LAND. AN UNEVENTFUL LNDG AND PARKING AT GATE WAS ACCOMPLISHED. NO EVASIVE ACTION ON OUR PART; NOR LGT Y'S; UNTIL THE CTLR ORDERED THE TURN. ALTHOUGH THE SEP WAS LESS THAN THE CTLR WOULD HAVE LIKED; NO DANGER OF A COLLISION EXISTED. LGT Y WOULD HAVE AND DID PASS BEHIND US.