The Effects of Shot Peening Treatment on the Hardness and Fatigue Strength of HQ 805

Machinery steels like HQ 805 are usually used in industrial application like shafts, wheels, and gears because of the combination between toughness and high strength. However, this materials are susceptible to damage because of fatigue. In overcoming the problem, surface modification by surface hardening is required. Shot peening is a conventional and low cost surface treatment which is efficient to increase fatigue strength. The effects of shot peening treatment on the hardness and fatigue strength on HQ (High Quality) 805 machinery steel were investigated in this paper. Shot peening treatment was conducted to the surface of HQ 805 material by using steel ball with 0.6 mm diameter and 40-50 HRC roughness. It was conducted with 7 bar compressor pressure, 100 mm shot distance from the nozzle to the sample surface in 10, 20 and 30 minutes shot duration. The effects of shot peening duration were investigated. The hardness test was conducted using micro Vickers hardness test method, the surface roughness was measured by using Surfcom profilometer 120 A, the fatigue strength was measured by using rotating bending machine, whereas surface morphology was observed by using SEM. It was found out that shot peening increase the hardness and fatigue strength of HQ 805 material. The hardness increased from 327 to 481 HVN, whereas the fatigue strength increased 29.5 % from 401 to 518 Mpa.