In some examples, a material may be subject to shot peening of a relatively long duration to improve cavitation erosion resistance of the material. For example, the material surface may be shot peened to cause grain reduction and an increase in hardness to a depth of 60 m or more, while the surface remains relatively smooth. As one example, the method may include treating a surface of austenitic stainless steel by impacting the surface with shot media for a treatment duration of 15 to 40 minutes at a shot peening intensity corresponding to an Almen strip type A intensity of 5A to 10A.

In a trial peening step, a shot peening process is applied to a back face 40B of a mold 40 in which an opening of a closed-end water cooling hole 42 is formed. Next, in an evaluation step, compressive residual stress and surface roughness of a region shot-peened in the trial peening step are measured and an extent of shot peening treatment in the trial peening step is evaluated based on measurement results. Next, in a peening step, a surface of the water cooling hole 42 in the mold 40 is shot-peened under peening conditions set based on peening conditions for the trial peening step and on evaluation results produced in the evaluation step.

There is disclosed a high-hardness atomized powder comprising in mass %: 2 to 8% of B; and one or two or more of Ti, Cr, Mo, W, Ni, Al, and C in an amount satisfying the following expression:
0(Ti %/10)+(Cr %/25)+(Mo %/10)+(W %/6)+(Ni %/10)+(Al %/10)+(C %/1)1.00,
the balance being Fe and unavoidable impurities, and having a particle diameter of 75 m or less. The powder, which has high hardness and is inexpensive, is particularly suitable for a powder for a projecting material for shot peening.

In an exhaust gas purification apparatus or other apparatuses that are supplied with ammonia generated from a urea aqueous solution and causes selective reduction and purification of nitride oxides, a shot peening treatment is applied to a welded portion of its exhaust pipe which is made of a ferritic stainless steel plate and through which exhaust gas containing ammonia and hydrogen passes. By shot peening the welded portion of the exhaust pipe, a tensile residual stress in the welded portion of the exhaust pipe can be replaced with a compressive residual stress, and further the diameter of metal crystal grains in the welded portion can be reduced. In this way, the durability of the exhaust pipe can be improved.

A process for manufacturing a V-pulley is disclosed. A metallic cylindrical pulley blank is integrally formed by removing material of a circumferential surface of the pulley blank to form a plurality of circumferential V-belt grooves. The pulley blank is subjected to precision machining and shot blasting to form a rough shot blasting layer on the side surfaces of the V-belt grooves. At least one through hole is axially drilled along a longitudinal central axis of the pulley blank from one axial end to opposite axial end of the shot blasted pulley blank to fluidly connect all of plurality of V-belt grooves followed by mounting and fastening a mold for casting tooth rings at the bottoms of the plurality of V-belt grooves and receiving a metal casting fluid into the plurality of V-belt grooves from one end portion of the through hole to form the tooth rings.

In a trial peening step, a shot peening process is applied to a back face 40B of a mold 40 in which an opening of a closed-end water cooling hole 42 is formed. Next, in an evaluation step, compressive residual stress and surface roughness of a region shot-peened in the trial peening step are measured and an extent of shot peening treatment in the trial peening step is evaluated based on measurement results. Next, in a peening step, a surface of the water cooling hole 42 in the mold 40 is shot-peened under peening conditions set based on peening conditions for the trial peening step and on evaluation results produced in the evaluation step.