A powder admixture useful for making a sintered valve seat insert includes a first iron-base powder and second iron-base powder wherein the first iron-base powder has a higher hardness than the second iron-base powder, the first iron-base powder including, in weight percent, 1-2% C, 10-25% Cr, 5-20% Mo, 15-25% Co, and 30-60 wt. % Fe, and the second iron-base powder including, in weight %, 1-1.5% C, 3-15% Cr, 5-7% Mo, 3-6% W, 1-1.7% V, and 60-85% Fe. The powder admixture can be sintered to form a sintered valve seat insert optionally infiltrated with copper.

A method of improving corrosion resistance of a cylinder cover including a port that is an intake port or an exhaust port. The cylinder cover is configured such that an annular cooling water passage is formed between an inner peripheral surface of the port and a valve seat ring when the valve seat ring is inserted in the port. The method includes forming a weld overlay layer on each of sealed regions of the inner peripheral surface of the port by laser metal deposition using a welding material made of a nickel-based alloy, a copper alloy, stainless steel, or a titanium alloy, the sealed regions being positioned at both sides of the cooling water passage, respectively.

A layer-sintered valve seat ring is disclosed. The layer-sintered valve seat ring includes at least two materials including a function material for a tribological contact with an opposite runner and a support material for the function material. The support material includes: C: 0.5 to 1.8% by weight; Cr: 3 to 16% by weight; Mo: 1 to 5% by weight; W: 0.5 to 5.5% by weight; V: 0.4 to 4.0% by weight; Cu: 12 to 25% by weight; Fe: 41.3 to 82.6% by weight; Mn: up to 0.6% by weight; Si: up to 1.8% by weight; and a remainder of production-related contamination in the form of at least one of Ni, Co, Ca, P, and S that are present in contents of <0.3% by weight each.

A layer-sintered valve seat ring is disclosed. The layer-sintered valve seat ring includes at least two materials including a function material for a tribological contact with an opposite runner and a support material for the function material. The support material includes: C: 0.5 to 1.8% by weight; Cr: 3 to 16% by weight; Mo: 1 to 5% by weight; W: 0.5 to 5.5% by weight; V: 0.4 to 4.0% by weight; Cu: 12 to 25% by weight; Fe: 41.3 to 82.6% by weight; Mn: up to 0.6% by weight; Si: up to 1.8% by weight; and a remainder of production-related contamination in the form of at least one of Ni, Co, Ca, P, and S that are present in contents of <0.3% by weight each.

The present invention addresses the problem of providing a sintered alloy valve guide capable of inhibiting valve adhesion even in a high-temperature environment. The problem can be solved by a sintered alloy valve guide impregnated with a lubricating oil including pores that are sealed on the valve guide outer circumferential surface. More particularly, the problem is solved by the sealing step of performing a sealing treatment of pores on the outer circumferential surface of a sintered body impregnated with a lubricating oil.

The disclosure includes manufacturing a semimanufactured cylinder head (3) having a shielding curtain portion (16g) and spraying metal powder (P) onto an annular valve seat portion (16f) using a cold spray method to form a valve seat film (16b). The shielding curtain portion (16g) projects in an annular shape from an annular edge portion of an opening portion (16a) of an intake port (16) or an opening portion (17a) of an exhaust port (17) toward the center (C) of the port. The annular valve seat portion (16f) is located on an outer side of the port than the shielding curtain portion (16g).

A method of preparing an engine valve is provided. The method includes hot forging a heat resistant steel at 1,150 to 1,250° C. to mold a valve, aging the molded valve and hollowed-out processing the aging valve. Additionally, the method includes nitride-heating the hollow valve and grinding a surface of a neck of the nitride-heated valve to remove a nitride layer.

A method of preparing an engine valve is provided. The method includes hot forging a heat resistant steel at 1,150 to 1,250° C. to mold a valve, aging the molded valve and hollowed-out processing the aging valve. Additionally, the method includes nitride-heating the hollow valve and grinding a surface of a neck of the nitride-heated valve to remove a nitride layer.

An iron-based alloy includes, in weight percent, carbon from about 0.75 to about 2 percent; manganese from about 0.1 to about 1 percent; silicon from about 0.1 to about 1 percent; chromium from about 3 to about 6 percent; nickel up to about 4 percent; vanadium from about 1 to about 3 percent; molybdenum from about 4 to about 7 percent; tungsten from about 4 to about 7 percent; cobalt from about 4 to about 7 percent; boron up to about 0.1 percent; nitrogen from about 0.001 to about 0.15 percent, aluminum from about 0.001 to about 0.6 percent, copper from about 0.1 to about 1 percent, sulfur up to about 0.3 percent, phosphorus up to about 0.3 percent, up to about 5 percent total of tantalum, titanium, hafnium and zirconium; iron from about 65 to about 80 percent; and incidental impurities. The alloy is suitable for use in elevated temperature applications such as in valve seat inserts for combustion engines.

An iron-based alloy includes, in weight percent, carbon from about 0.75 to about 2 percent; manganese from about 0.1 to about 1 percent; silicon from about 0.1 to about 1 percent; chromium from about 3 to about 6 percent; nickel up to about 4 percent; vanadium from about 1 to about 3 percent; molybdenum from about 4 to about 7 percent; tungsten from about 4 to about 7 percent; cobalt from about 4 to about 7 percent; boron up to about 0.1 percent; nitrogen from about 0.001 to about 0.15 percent, aluminum from about 0.001 to about 0.6 percent, copper from about 0.1 to about 1 percent, sulfur up to about 0.3 percent, phosphorus up to about 0.3 percent, up to about 5 percent total of tantalum, titanium, hafnium and zirconium; iron from about 65 to about 80 percent; and incidental impurities. The alloy is suitable for use in elevated temperature applications such as in valve seat inserts for combustion engines.