At a diameter-decreasing operation during manufacture of a poppet valve, an intermediate stem portion at which a valve head portion and an intermediate stem portion are made integral by way of a neck portion may be inserted between/among diameter-decreasing tools. Application of compressive forces from compressing surfaces of the diameter-decreasing tools may cause a part of the intermediate stem portion to be decreased in diameter and may cause a main body portion of a first stem portion to be formed and may cause formation of a stepped portion which is continuous with the main body portion, and formation, by an absence of decrease in diameter, of a second stem portion which is broader in girth than the main body portion and which is continuous with the neck portion and which is also continuous with the main body portion by way of the stepped portion.

A system to attach valve seat inserts to an aluminum cylinder head of an automobile vehicle includes a cylinder head of an automobile vehicle engine having a valve seat portion. A valve seat insert is positioned in the valve seat portion of the cylinder head. A fusion bond is created between the valve seat insert and the valve seat portion by laser welding thereby fusing the valve seat insert to the valve seat portion.

A system to attach valve seat inserts to an aluminum cylinder head of an automobile vehicle includes a cylinder head of an automobile vehicle engine having a valve seat portion. A valve seat insert is positioned in the valve seat portion of the cylinder head. A fusion bond is created between the valve seat insert and the valve seat portion by laser welding thereby fusing the valve seat insert to the valve seat portion.

A low-carbon iron-chromium-molybdenum alloy comprises, in weight percent: carbon from about 0.1 to about 0.8 percent; manganese from about 0.1 to about 4 percent; silicon from about 0.1 to about 0.5 percent; chromium from 14 to about 16 percent; nickel up to about 8 percent; vanadium up to about 0.1 percent; molybdenum from 14 to about 16 percent; tungsten up to about 6 percent; niobium from about 0.1 to about 0.8 percent; cobalt up to about 0.2 percent; boron up to 0.1 percent; nitrogen up to about 0.1 percent; copper up to about 1.5 percent; sulfur up to about 0.05 percent; phosphorus up to about 0.05 percent; balance iron from about 50 to about 65 percent; and incidental impurities wherein the alloy contains a ratio of Cr/Mo of about 0.9 to about 1.1. The alloy can be used as a valve seat insert for combustion engines.

A low-carbon iron-chromium-molybdenum alloy comprises, in weight percent: carbon from about 0.1 to about 0.8 percent; manganese from about 0.1 to about 4 percent; silicon from about 0.1 to about 0.5 percent; chromium from 14 to about 16 percent; nickel up to about 8 percent; vanadium up to about 0.1 percent; molybdenum from 14 to about 16 percent; tungsten up to about 6 percent; niobium from about 0.1 to about 0.8 percent; cobalt up to about 0.2 percent; boron up to 0.1 percent; nitrogen up to about 0.1 percent; copper up to about 1.5 percent; sulfur up to about 0.05 percent; phosphorus up to about 0.05 percent; balance iron from about 50 to about 65 percent; and incidental impurities wherein the alloy contains a ratio of Cr/Mo of about 0.9 to about 1.1. The alloy can be used as a valve seat insert for combustion engines.

A nickel-niobium intermetallic alloy contains, in weight percent, silicon from about 1.5 to about 3.5 percent; chromium from 5 to about 15 percent; nickel from about 45 to about 75 percent; niobium from about 14 to about 30 percent; cobalt up to about 7 percent; and iron up to about 10 percent; wherein the nickel plus niobium content is about 70 to about 90 percent and the total silicon, chromium, cobalt and iron content is about 10 to about 30 percent. The alloy can have a cast microstructure of at least 95 volume percent intermetallic phases and no more than about 5 volume percent solid solution phases. The intermetallic phases can include rod-like intermetallic phases of Ni.sub.3Nb and Ni.sub.8Nb.sub.7. The microstructure can be a lamellar microstructure and/or the microstructure can have less than 5 volume percent Ni—Fe and Ni—Co rich intermetallic phases.

A nickel-niobium intermetallic alloy contains, in weight percent, silicon from about 1.5 to about 3.5 percent; chromium from 5 to about 15 percent; nickel from about 45 to about 75 percent; niobium from about 14 to about 30 percent; cobalt up to about 7 percent; and iron up to about 10 percent; wherein the nickel plus niobium content is about 70 to about 90 percent and the total silicon, chromium, cobalt and iron content is about 10 to about 30 percent. The alloy can have a cast microstructure of at least 95 volume percent intermetallic phases and no more than about 5 volume percent solid solution phases. The intermetallic phases can include rod-like intermetallic phases of Ni.sub.3Nb and Ni.sub.8Nb.sub.7. The microstructure can be a lamellar microstructure and/or the microstructure can have less than 5 volume percent Ni—Fe and Ni—Co rich intermetallic phases.

An internal combustion engine includes an engine block, a piston, a cylinder head, and a valve train. The engine block includes a cylinder block including a cylinder bore and a crankcase defining a crankcase chamber with a crankshaft positioned within the crankcase chamber. The piston is coupled to the crankshaft and configured to reciprocate within the cylinder bore. The cylinder head is coupled to the cylinder block. The valve train includes a camshaft, a first and second pushrod, a first and second rocker arm, an exhaust valve housed, and an intake valve. The first rocker arm, the second rocker arm, the exhaust valve, and the intake valve each include at least a layer of a low friction material. The first and second pushrod each pass through a pushrod seal to prevent fluid from reaching the rocker chamber to fluidly isolate the rocker chamber from the crankcase chamber.

An internal combustion engine includes an engine block, a piston, a cylinder head, and a valve train. The engine block includes a cylinder block including a cylinder bore and a crankcase defining a crankcase chamber with a crankshaft positioned within the crankcase chamber. The piston is coupled to the crankshaft and configured to reciprocate within the cylinder bore. The cylinder head is coupled to the cylinder block. The valve train includes a camshaft, a first and second pushrod, a first and second rocker arm, an exhaust valve housed, and an intake valve. The first rocker arm, the second rocker arm, the exhaust valve, and the intake valve each include at least a layer of a low friction material. The first and second pushrod each pass through a pushrod seal to prevent fluid from reaching the rocker chamber to fluidly isolate the rocker chamber from the crankcase chamber.

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.