Experimental Investigation to Increase the Life of Gearbox Bushes used in General Engineering Applications

Abstract

As the need for interchangeable parts which require grinding limits of 0.025 mm or less has increased, components which can withstand load and give more life are required. Nitriding is an important thermo-chemical surface treatment that is used to improve the wear and corrosion resistance as well as the fatigue endurance of steel parts. The Nitriding process is a method of obtaining very high surface hardness with a minimum of distortion and can be done at temperatures which permit complete finishing of the object to be nitrided before the operation. This is a great advantage over the cyanide process or the case hardening process. The inherent disadvantage of case hardened parts is warpage particularly those made from certain grades of steel and of non uniform sections. The cost of the scrap due to rejections has been high and a process of heat treating which would eliminate losses caused by distortion in finished parts would be of great advantage. The Cylinders and Pistons which form an important part of the general engineering use undergo large number of cycles. Due to the high utilization these parts are to be surface hardened to delay the early worn out situation. In the present paper, surface hardening of bushes made of 17-4 PH material by nitriding at different case depths are studied to see the suitability of replacement of bushes in gear box and in general engineering applications, to reduce the replacement of spares and also breakdown maintenance costs is attempted. The precipitation hardening steel (17-4PH) used in critical areas of the Nuclear Power Plants where the situation demands highly surface hardened parts. The experimental work is carried by simulating the actual use of bush in a gear box of a Granite Cutting Machine. The life of bush made of various materials and with different case depths in the nitriding process is obtained from simulated process. The bush made of 17-4 PH material with 0.15 mm nitriding case depth could withstand more number of cycles than that of bushes made of other materials.